GFA Aerotowing Manual

Transcription

THE GLIDING FEDERATION OF AUSTRALIA
AEROTOWING MANUAL
OPS 0003 - GFA Aerotowing Manual
December 2006
AEROTOWING MANUAL
The reference document for the assessment of competency of tug
pilots and the issuing of Towing Permits
Issue 3, December 2006
Published by:
The Gliding Federation of Australia
Building 130, Wirraway Road,
Essendon Airport, Victoria 3014,
Australia
ABN 99 008 560 263
Phone: (03) 0379 7411
Fax: (03) 9379 5519
Email: secretary@gfa.org.au
© Copyright – Gliding Federation of Australia, 2006
This issue of the Aerotowing Manual is approved by the Civil Aviation Safety
Authority
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Table of Contents
1.
2.
AEROTOWING - GENERAL POLICY ................................................................. 1
PILOTS ............................................................................................................... 1
2.1
HOW TO OBTAIN A GLIDER TOWING PERMIT ........................................ 1
2.2
VALIDITY AND RECENCY REQUIREMENTS FOR A GLIDER TOWING
PERMIT .................................................................................................................. 2
3. CASA DELEGATES ............................................................................................ 2
3.1
HOW TO BECOME A CASA DELEGATE ................................................... 2
3.2
VALIDITY AND RECENCY REQUIREMENTS FOR CASA DELEGATES .. 3
4. GLIDER TOWING PERMITS - “CHAIN OF COMMAND” .................................... 3
5. GFA MEMBERSHIP OF TUG PILOTS ............................................................... 3
6. PRIVILEGES, LIMITATIONS AND VALIDITY OF GLIDER TOWING PERMITS 4
6.1
GENERAL .................................................................................................... 4
6.2
GLIDER TOWING PERMIT ......................................................................... 4
6.3
CROSS-COUNTRY TOWING...................................................................... 4
6.4
DOUBLE TOWING APPROVAL .................................................................. 4
6.5
OUTLANDING RETRIEVE APPROVAL ...................................................... 4
6.6
VALIDITY OF GLIDER TOWING PERMITS ................................................ 4
6.7
VALIDITY OF CAR 149 GLIDER TOWING DELEGATIONS ....................... 5
7. PHILOSOPHICAL APPROACH TO TOWING GLIDERS .................................... 5
7.1
DESIRABLE BACKGROUND ...................................................................... 5
7.2
ASSESSMENT OF SUITABILITY ................................................................ 6
7.3
APPLICATION OF THE PROCEDURES IN THIS MANUAL ....................... 7
7.4
THE RELATIONSHIP OF GLIDING EXPERIENCE TO SUCCESSFUL
GLIDER-TOWING .................................................................................................. 7
8. COMPETENCY STANDARDS TO BE DEMONSTRATED FOR ISSUE OF
GLIDER TOWING PERMIT ........................................................................................ 7
8.1
NORMAL PROCEDURES ........................................................................... 7
8.1.1 Ground Preparation .................................................................................. 7
8.1.2 Take-off .................................................................................................... 8
8.1.3 Climb ........................................................................................................ 8
8.1.4 Release .................................................................................................... 9
8.1.5 Descent .................................................................................................... 9
8.1.6 Joining Circuit ........................................................................................... 9
8.1.7 Approach and Landing ........................................................................... 10
8.1.8 Cruising on Tow ..................................................................................... 10
8.1.9 Descending on Tow ................................................................................ 10
8.1.10 Further Considerations ....................................................................... 10
8.2
ABNORMAL PROCEDURES..................................................................... 10
8.2.1 “Stop” signal on take-off run ................................................................... 10
8.2.2 Partial power failure ................................................................................ 11
8.2.3 Glider airbrakes (or tail-chute) open during climb ................................... 11
8.2.4 Order to glider pilot to release ................................................................ 11
8.2.5 Glider unable to release ......................................................................... 11
8.2.6 Glider and tug unable to release ............................................................ 11
8.2.7 The “tug upset” ....................................................................................... 11
8.3
DOUBLE TOWING APPROVAL ................................................................ 11
8.3.1 Procedures ............................................................................................. 11
8.3.2 Pilot qualifications and operational requirements ................................... 12
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8.3.5 Notification.............................................................................................. 13
8.4
OUTLANDING RETRIEVE APPROVAL .................................................... 13
8.4.1 Prerequisites .......................................................................................... 13
8.4.2 Ground preparation ................................................................................ 13
8.4.3. Notification ............................................................................................ 14
9. EXPANDED GUIDELINES FOR GLIDER TOWING PERMIT ........................... 14
9.1
NORMAL PROCEDURES ......................................................................... 14
9.1.1 The purpose of an aerotow..................................................................... 14
9.1.2. Daily inspection ..................................................................................... 14
9.1.3 Performance of tug/glider combination ................................................... 15
9.1.4 Awareness of glider limitations ............................................................... 15
9.1.5 Glider airbrakes ...................................................................................... 16
9.1.6 Greater chance of engine failure in tugs ................................................. 16
9.1.7 Minimum fuel for tow .............................................................................. 17
9.1.8 Pre take-off checks ................................................................................. 17
9.1.9 Ground signals ....................................................................................... 18
9.1.10 Take-off technique .............................................................................. 19
9.1.11 The steady climb ................................................................................. 21
9.1.12 High-tow and low-tow.......................................................................... 22
9.1.13 “Boxing the slipstream” ....................................................................... 24
9.1.14 Releasing from tow ............................................................................. 25
9.1.15 The descent ........................................................................................ 25
9.1.16 Landing ............................................................................................... 26
9.1.17 Baulked approaches and go-arounds ................................................. 26
9.1.18 If in doubt, drop the rope ..................................................................... 26
9.1.19 Approaching too low ........................................................................... 27
9.1.20 Cruising on tow ................................................................................... 27
9.1.21 Descending on tow ............................................................................. 28
9.1.22 The Non-Manoeuvring Area (NMA) .................................................... 29
9.1.23 Some suggested towing patterns ........................................................ 29
9.2
ABNORMAL PROCEDURES..................................................................... 30
9.2.1 “Stop” signal during take-off run ............................................................. 30
9.2.2 Engine failure ......................................................................................... 30
9.2.3 Glider’s airbrakes coming open on ground-run....................................... 31
9.2.4 Glider’s airbrakes coming open during climb .......................................... 31
9.2.5 Other reasons for poor rate of climb ....................................................... 31
9.2.6 Order to glider pilot to release - the “wave-off” signal ............................. 32
9.2.7 Glider unable to release ......................................................................... 32
9.2.8 Double-release failure - landing on tow (optional - not mandatory for
Permit) .............................................................................................................. 33
9.3
THE “TUG UPSET” .................................................................................... 34
10. EXPANDED GUIDELINES FOR OUTLANDING RETRIEVE APPROVAL ........ 36
10.1 GENERAL .................................................................................................. 36
10.2 PRELIMINARIES ....................................................................................... 36
10.3 THE LANDING ........................................................................................... 37
10.3.1 Lack of markings ................................................................................. 37
10.3.2 Obstacles on the approaches ............................................................. 37
10.3.3 Lack of wind information ..................................................................... 37
10.3.4 Unreliable information and pressure to perform .................................. 37
10.3.5 Apply the glider pilots’ five ‘S’ rule ...................................................... 37
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10.3.6 Further reading ................................................................................... 39
10.3.7 Removing the rope ............................................................................. 39
10.4 THE TAKE-OFF ......................................................................................... 40
10.4.1 Pacing out the paddock ...................................................................... 40
10.4.2 Factors affecting the take-off .............................................................. 40
10.4.3 Take-off technique .............................................................................. 41
11. THE MANAGEMENT OF ENGINES AND RELATED ITEMS IN THE GLIDERTOWING ROLE ........................................................................................................ 42
11.1 AIR-COOLED HORIZONTALLY-OPPOSED ENGINES (LYCOMING,
CONTINENTAL, ETC) .......................................................................................... 42
11.1.1. General ............................................................................................... 42
11.1.2 Daily inspections ................................................................................. 42
11.1.3 Pilot operation ..................................................................................... 44
11.2 AIR-COOLED IN-LINE ENGINES (GYPSY MAJORS, ETC.) .................... 46
11.2.1 General ............................................................................................... 46
11.2.2 The “Armstrong” starter....................................................................... 47
11.3 LIQUID-COOLED ENGINES...................................................................... 49
11.3.1 Partially liquid-cooled engines ............................................................ 51
11.4 PROPELLERS ........................................................................................... 52
11.4.1 Fixed pitch propellers .......................................................................... 52
11.4.2 Variable-pitch and two-speed propellers ............................................. 52
11.4.3 Constant speed propellers .................................................................. 52
11.4.4 Cowl flaps ........................................................................................... 53
11.5 FUEL REQUIREMENTS, AVGAS AND MOGAS ....................................... 54
11.6 ROPES, RINGS AND WEAK-LINKS. ........................................................ 54
12. APPENDIX - MISCELLANEOUS INFORMATION AND STANDARD FORMS . 57
12.1 A TYPICAL GLIDER-TOWING PERFORMANCE CHART (PAWNEE 235)
57
12.2 CUTAWAY OF A TYPICAL TUG ENGINE (LYCOMING 0-540) ................ 58
12.3 EXTRACT FROM CIVIL AVIATION REGULATIONS - DAILY INSPECTION
SCHEDULE .......................................................................................................... 59
12.4 EXTRACT FROM CIVIL AVIATION REGULATIONS - PERMISSIBLE
MAINTENANCE BY PILOTS ................................................................................ 61
12.5 COMPETENCE CHECK LIST - INITIAL GLIDER-TOWING PERMIT ........ 62
12.6 COMPETENCE CHECK LIST - DOUBLE TOWING APPROVAL .............. 64
12.7 COMPETENCE CHECKLIST - OUTLANDING RETRIEVE APPROVAL ... 65
12.8 GLIDER TOWING PERMIT, DOUBLE TOWING AND OUTLANDING
RETRIEVE APPROVALS ..................................................................................... 66
12.9 CIVIL AVIATION REGULATIONS (CARS) 92 AND 93 - USE OF
AERODROMES .................................................................................................... 67
12.10 CIVIL AVIATION ADVISORY PUBLICATION (CAAP) 92-1, GUIDELINES
FOR AEROPLANE LANDING AREAS ................................................................. 68
12.11 EXTRACT FROM AERONAUTICAL INFORMATION PUBLICATION
(AIP) - DAYLIGHT/DARKNESS GRAPHS (END OF DAYLIGHT ONLY) ............. 74
12.12 CONVERSION OF ARC TO TIME ......................................................... 78
12.13 CROSSWIND COMPONENT CHART.................................................... 79
13. SELF-TEST QUESTIONS AND ANSWERS ..................................................... 80
13.1 GLIDER-TOWING PERMIT – QUESTIONS .............................................. 80
13.2 GLIDER TOWING PERMIT – ANSWERS ................................................. 84
13.3 DOUBLE TOWING APPROVAL – QUESTIONS ....................................... 88
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13.4 DOUBLE TOWING APPROVAL – ANSWERS .......................................... 89
13.5 OUTLANDING RETRIEVE APPROVAL – QUESTIONS ........................... 90
13.6 OUTLANDING RETRIEVE APPROVAL – ANSWERS .............................. 91
NOTES FOR DELEGATES ...................................................................................... 93
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AEROTOWING MANUAL
1.
AEROTOWING - GENERAL POLICY
The aerotowing of gliders is only permitted by pilots whose competence for
the task has been assessed and who hold a Glider Towing Permit. The
Permit is subject to certain recency requirements.
A Glider Towing permit is issued by a Delegate of the Civil Aviation Safety
Authority (CASA) under Civil Aviation Regulation (CAR) 149 only when the
delegate has assessed the pilot as competent in glider towing operations.
2.
PILOTS
2.1
HOW TO OBTAIN A GLIDER TOWING PERMIT
Candidates for glider-towing approval must hold a Private or higher category
licence and a minimum of 100 hours total aeronautical experience, of which
at least 40 hours shall be on CASA-registered Australian or overseasregistered fixed-wing aircraft. Of the remaining experience, glider, military
(fixed wing) and ultralight (3-axis control) flying time may be counted in full
toward the total aeronautical experience.
As glider tugs exist in a wide variety of types, the candidate must hold the
endorsements (e.g. tailwheel, constant-speed) applicable to the type to be
used for towing.
A gliding certificate is strongly recommended and may be mandatory in
some clubs. As a minimum, the candidate must be in current practice as a
glider pilot in an aerotow environment before issue of a towing permit. This
currency shall include exposure to the various tug signals, to ensure
familiarity from the glider end.
When the above conditions are satisfied, the candidate may commence
glider-towing in a double-control aircraft with the CASA delegate or an
experienced tug pilot nominated by a delegate as pilot in command. The
applicant must demonstrate competency to the CASA delegate and the
delegate will issue a Glider Towing Permit if satisfied the pilot is competent.
A Glider Towing Permit authorises a pilot to tow one glider at a time from
marked aerodromes and/or established gliding sites only, unless further
privileges are annotated.
The privileges, limitations and revalidation
requirements of a Glider Towing Permit are notified on the Permit.
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2.2
VALIDITY AND RECENCY REQUIREMENTS FOR A GLIDER
TOWING PERMIT
A Glider Towing Permit remains valid as long as the pilot’s licence (i.e.
medical certificate and flight review) is current and the pilot meets recency
requirements. The recency requirements for glider towing are notified on the
Glider Towing Permit.
Note: The Glider Towing Permit is issued by the CASA delegate for the
period stated on the Permit. This is normally while the holder of the Permit
holds a valid licence and medical certificate.
The longer a tug pilot has lacked the recency requirements of the Permit, the
longer it is likely to take to satisfy the delegate of his/her competence to
obtain recency by this means.
3.
CASA DELEGATES
3.1
HOW TO BECOME A CASA DELEGATE
Experienced pilots may make an application to become a CASA delegate for
the issue of Glider Towing Permits. Application will be to CASA via the GFA
RTO/Operations responsible for the applicant’s club and with the
recommendation of the GFA Chief Technical Officer – Operations. The GFA
will expect delegates to be endorsed by a gliding club or organization.
Experience requirements to be recommended by GFA to hold a CASA
delegation are as follows:
A Private or higher category licence;

Significant relevant aeronautical experience, including;
o A minimum of 175 hours total aeronautical experience, at least 100 of
which must be in aeroplanes;
o A minimum of 50 hours glider towing experience (more if overall
experience is close to the minimum);

Must have held a Glider Towing permit, with privileges including
outlanding retrieve approval, for at least twelve months;

Must have a demonstrated aptitude for assessing the competence of
pilots for the glider towing task.
If the above conditions are satisfied, and subject to the recommendation of a
representative of the GFA, the candidate may apply for a CASA delegation
as described above. Successful applicants will be appointed as CASA
delegates by means of a CASA Instrument of Delegation.
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Refer also to the notes for CASA delegates in Appendix 1 to this manual on
page 93.
3.2
VALIDITY AND RECENCY REQUIREMENTS FOR CASA
DELEGATES
A CASA Instrument of Delegation is valid for the period stated in the
Instrument of Delegation. Recency requirements are the same as for a
Glider Towing Permit.
Refer also to Notes for CASA delegates in Appendix 1 to this manual on
page 93.
4.
GLIDER TOWING PERMITS - “CHAIN OF COMMAND”
To sum up Sections 2 and 3, the chain of command for Glider Towing
permits is as follows :CASA delegates
Holders of CASA Instruments of Delegation for the issue of Glider towing
permits. Subject to renewal by CASA (normally on GFA recommendation),
which may entail CASA surveillance of the applicant’s activities.
Tug pilots
Assessed by a CASA delegate in accordance with the procedures described
in this manual. Issued with Glider Towing Permit by CASA delegate. If
recency requirements are met the holder may exercise the privileges of the
Permit. If the six-month recency requirements are not met (see 13.1.3) the
tug pilot must satisfy a delegate of his/her competence, which the delegate
may signify by signing the holder’s personal flying log book.
5.
GFA MEMBERSHIP OF TUG PILOTS
Although it is not strictly a requirement that a tug-pilot be a member of the
Gliding Federation of Australia, such membership confers the protection of
the various GFA insurances on the pilot and becoming a member would be a
wise move.
It is important to note that a tug pilot who is not a member of the GFA has no
protection from the Federation’s Broad-Based Liability (BBL) or Contingent
Liability policies.
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6.
PRIVILEGES, LIMITATIONS AND VALIDITY OF
GLIDER TOWING PERMITS
6.1
GENERAL
A Glider Towing Permit authorises the holder to act as pilot in command of
an aeroplane in glider-towing operations in such a way as not to endanger
any other traffic. It is recommended that a tug aircraft should not be flown
within 100 metres horizontally or 200 feet vertically of another aircraft, except
in the case of establishing such separation from a glider or gliders released
by that tug aircraft.
6.2
GLIDER TOWING PERMIT
The holder of a Glider Towing Permit in its simplest form may tow a single
glider in operations from a Licensed Aerodrome or from an established and
suitably marked gliding site approved by the GFA and which meets the
requirements of an Aircraft Landing Area.
6.3
CROSS-COUNTRY TOWING
Cross-country glider tows from and to such aerodromes or sites as
described in 6.2 are permitted by a pilot holding the appropriate licence for
carrying out such flights (This means pilots holding a private or higher
category licence, or the old “Unrestricted” licence may carry out such tows.
Pilots still holding the old “Restricted” licence may not carry out such tows,
unless the planned destination is within a designated training area
associated with the departure aerodrome).
No double towing or outlanding retrieves are permitted unless these
activities are authorised by the holder’s Glider Towing Permit. See below.
6.4
DOUBLE TOWING APPROVAL
The holder of a Glider Towing Permit which includes double towing may tow
two gliders in accordance with the procedures laid down in this manual and
notified on the approval document.
6.5
OUTLANDING RETRIEVE APPROVAL
As notified by the approval document, the holder of a Glider Towing Permit
which includes outlanding retrieve approval may launch gliders from
unmarked paddocks and is authorised to land in such paddocks solely for
the purpose of launching a glider, subject to the approval of the land-owner.
6.6
VALIDITY OF GLIDER TOWING PERMITS
Glider Towing Permits shall be valid for the period shown on the Permit.
This is normally the period of validity of the holder's Flight Crew Licence
(Aeroplanes), subject to the recency requirements of the Permit being met.
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6.7
VALIDITY OF CAR 149 GLIDER TOWING DELEGATIONS
CASA Instruments of Delegation are valid for the period shown on the
Instrument, provided the delegate holds a current Glider Towing permit, and
are subject to the conditions specified in the Instrument of Delegation.
CASA will normally seek the GFA’s recommendation before issuing or
renewing a delegation.
7.
PHILOSOPHICAL APPROACH TO TOWING GLIDERS
Although it seems to state the obvious, the sole task of the tug pilot is to
launch gliders as safely and efficiently as possible. The reason it is
mentioned here is that tug pilots sometimes forget this basic fact and seem
to acquire a belief that the glider is almost secondary to the business of
flying a tug aircraft. Thus we get problems like towing too far away, towing
downwind, towing into the sun for long periods, rough handling, excessively
steep turning, "cowboy" descent patterns, etc. Tug pilots may sometimes
need reminding that they exist solely for the benefit of the glider pilots and if
they do not adhere to legal requirements and/or the operating procedures
set by the club, they may be shown the door.
7.1
DESIRABLE BACKGROUND
Most tugs are “taildraggers” and it is becoming increasingly difficult to obtain
training on this type of aircraft in the mainstream flying schools, almost all
school aircraft being nosewheel designs. A small number of flying schools
specialise in taildragger endorsements, often together with aerobatics.
Alternatively, new pilots considering glider-towing as another string to their
bow are strongly recommended to join the Australian Ultralight Federation
(AUF) and do some flying at one of their schools in one of the more
demanding taildragger machines such as the Lightwing or Skyfox, as these
are likely to have flying characteristics (but not the mass) closer to the type
of aircraft they will be using to tow gliders.
Experience has shown that the best tug pilots are light aircraft pilots with a
strong VFR background in aircraft which are quite demanding to fly, such as
Austers, Cessna 180s and the ultralights mentioned above.
Pilots
experienced on such aircraft tend to have good "hands on" skills and their
lookout is of a good enough standard for gliding clubs to rely on.
Another reason to insist on a good background in a relevant aircraft type is
that a tug pilot has to put up with a pressure to fly which was not present
before. For example, if conditions get a bit tricky (e.g. crosswind), the glider
pilots may be quite happy to keep flying but the tug pilot may never have
flown in such conditions before. With glider pilots breathing down his neck to
be launched, it is much more difficult to choose to stop flying than it was
before. This is where any lack of experience becomes apparent, sometimes
resulting in an accident or incident. Delegates may be disinclined to issue
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Permits to pilots who lack the experience and/or competence to handle such
conditions, or recommend they consolidate their skills with a flying school.
Additionally, it is worth remembering that the kind of turbulent conditions that
upset some power-pilots are the very conditions sought by glider pilots and a
tug pilot will be going up and down all day in these conditions, rather than
climbing to cruise in the smooth air on top of the turbulent layer.
Finally, delegates and gliding clubs should beware of pilots who have
learned to fly on tricycle-gear aircraft, then do a minimal conversion to an
easy-to-fly taildragger like a Citabria and appear at a gliding club wanting to
start a towing conversion. If such pilots have a strong gliding background,
they are usually not a problem, gliders needing good hands-on skill to
operate safely and many of them being of taildragger design. If they have no
gliding background and only a minimal taildragger conversion, they need to
be watched very carefully. Although everybody has to start somewhere and
some pilots do adapt very well, others never really cope and either need
extra work back at the flying school or decide that aerotowing is not for them.
7.2
ASSESSMENT OF SUITABILITY
Keeping in mind the desirable background outlined above, the CASA
delegate’s task is to make an assessment of the pilot's suitability for the
aerotowing task. Most CASA delegates are not powered flight instructors
and therefore have no privileges to train and endorse pilots for taildragger or
constant-speed conversions. Their job in most cases will be simply to make
an assessment of whether the person really has the background and
aptitude to tow gliders, or whether further taildragger training back at the
flying school is required.
Unfortunately, a common complaint made by CASA delegates is that pilots
fresh from flying training are often good on procedures and use of radio, but
not so good in raw flying ability and airmanship. Under the pressure of
having a glider on the back and coping with having to think for two aircraft
instead of one, a marginal pilot's airmanship may fall to a negligible level. It
is hard to imagine a more hazardous situation than the command pilot of a
tug/glider combination who is too stressed to look out. Tug aircraft climb and
descend through a very busy part of the sky many times in a day and the
pilot's airmanship must be of the finest quality.
Correct engine-handling is important. Light aircraft engines are air-cooled
and spend most of their lives at constant power and a constant cruising
speed. In this environment air-cooling is very effective, as there are no rapid
changes to power or speed. Cylinder-head and oil temperatures remain
constant and the engine is thermally stable.
The demands of glider-towing are quite different and very demanding on an
engine. The cycle of high power, low airspeed, followed by lower power,
higher airspeed, results in a "thermal gradient" from front to rear of the
engine. This is worsened if a pilot allows a very rapid speed build-up and/or
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closes the throttle too quickly after the glider has released, adding the
problem of "thermal shock" to the gradient problem already present.
Any pilot who shows signs of rough handling of the throttle, and is not
amenable to this characteristic being corrected, will not make a good tug
pilot and is likely to cost the club dearly if allowed to escape onto the tug pilot
roster. Gliding clubs should consider carefully whether they want such pilots
to be in charge of a major asset before they roster them for duty without retraining.
7.3
APPLICATION OF THE PROCEDURES IN THIS MANUAL
If the pilot is assessed as being suitable material to become a tug pilot, the
procedures outlined in this manual may be applied. The procedures are selfexplanatory; the only comment needed here is to ensure that none of it is
skimped.
7.4
THE RELATIONSHIP OF GLIDING EXPERIENCE TO
SUCCESSFUL GLIDER-TOWING
Although not a requirement that a tug pilot also retains currency as a solo
glider pilot (but it may be mandatory in some clubs), there is general
agreement that the best tug pilots are also glider pilots. Glider pilots are
skilled at "reading" the sky. They are aware of areas of lift and sink and
know how to seek out or avoid such areas. This kind of ability is valuable for
a tug pilot, as maximum use of lift during the climb and managing to find
areas of sink on the descent can greatly reduce the time taken for each tow.
This maximises efficiency and reduces costs, but must never be at the
expense of top-quality airmanship, especially lookout, at all times.
8.
COMPETENCY STANDARDS TO BE DEMONSTRATED
FOR ISSUE OF GLIDER TOWING PERMIT
8.1
NORMAL PROCEDURES
There is no specific number of hours or flights to be completed; it is left to
the discretion of the CASA delegate to issue a Glider Towing Permit when
the applicant demonstrates the necessary level of competence.
An applicant must be able to show understanding and application of the
knowledge and skills listed below.
8.1.1
Ground Preparation

The tug pilot's responsibility for the overall safety of the towing operation,
as command pilot of the tug/glider combination.

The tug's Flight Manual Towing Supplement and Towing Performance
Chart, if applicable.
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8.1.2
8.1.3

The requirements of the GFA Operational Regulations and Operations
Manual in respect of the aerotowing of gliders.

Preparation of aircraft for glider towing operations, including inspection of
tug aircraft release mechanism, mirrors, ropes, release rings and weak
links.

The glider's requirements in aerotowed flight, including maximum and
minimum speeds in unballasted and ballasted configurations.

The implications of glider towing on the fuel consumption of the tug
aircraft.

Minimum rope lengths for the single and, if applicable, double towing of
gliders.

Weak link requirements.

Ground signals applicable to glider towing.

Assess the take-off performance required when towing a glider against
the distance available under prevailing conditions.
Take-off

Correct response to all ground signals.

Monitor expected take-off performance and take appropriate action in the
event of not achieving expected performance.

Demonstrate ability to take-off in a crosswind of not less than 2/3 of the
maximum allowable crosswind for the type.

Use of mirrors to monitor glider position.
Climb

Fly primarily by attitude to maintain a speed appropriate to the tug/glider
combination and the conditions, responding only to trends in airspeed
and smoothing out transient changes in speed caused by turbulence.

Correct handling of engine, using power settings appropriate to the
engine handling notes and the requirements of the tug/glider
combination.

Maintain a good lookout and adequately compensate for any aircraft blind
spots. This means avoiding long periods at a constant heading and, in
high-wing tugs, raising a wing to check that the airspace is clear before
turning.
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8.1.4
8.1.5
8.1.6

Selection of towing pattern which minimises towing into the sun, takes
advantage of forced landing options, stays within gliding range of the field
and makes maximum use of any lift which is available. The towing
pattern should also take into account the wind velocity and likely release
position.

Avoidance of conflict with other traffic, glider and power, in the circuit
area.

Continue to monitor glider position by use of mirrors.

Recognise high-tow and low-tow and transition between the two.

Control the tug attitude during “boxing the slipstream” by the glider.

Maintain correct towing attitude and speed regardless of whether glider is
in high or low tow, is out of position or is transiting between towing
positions.

Ensure tug attitude and heading are controlled when glider is taken as far
out of position as practicable and safe, in order to demonstrate to tug
pilot the required action under these circumstances.
Release

Confirm glider release by use of mirrors and, if possible and necessary,
by physically turning round in seat to view glider directly.

Ensure airspace below tug aircraft is clear to commence descent.
Descent

Commence descent, maintaining heading or turning left as required,
avoiding abrupt manoeuvres or shock-cooling of engine. Do not turn
right, as some tugs (e.g. Cessnas, Maules, two-seat Pawnees, etc), have
a blind spot on the right side of the cockpit and it is not possible to
adequately clear the airspace into which the aircraft is just about to
commence descent.

Selection of correct airspeed and power settings.

Selection of descent pattern appropriate to the site, wind velocity and
other traffic.

Maintain adequate lookout at all times, compensating for aircraft blind
spots.
Joining Circuit

Correct circuit entry, maintaining good lookout, integrating with other
traffic and making appropriate radio calls.
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8.1.7
8.1.8
8.1.9

Carry out pre-landing checks.

Selection of suitable landing area, with due regard for any special
requirements which may be in force.
Approach and Landing

Recognition of trailing rope and the required obstacle clearance.
Awareness of option to drop rope if required.

Go-around procedures.
Cruising on Tow

Gentle transition into cruise and gentle reduction of power, in order to
avoid slack developing in the rope.

Selection of appropriate speeds in accordance with conditions and glider
placard limitations.
Descending on Tow

Gentle closure of throttle, avoiding slack in rope and giving glider pilot
time to adjust airbrake setting to maintain position.

Maintain adequate lookout and select descent path appropriate to the
requirements of the combination.

If intending to land on tow, remember obstacle clearance in relation to the
position of the glider and the selection of intended touchdown point.
8.1.10 Further Considerations
8.2

The foregoing list of normal (non-emergency) aerotowing procedures is
based on the towing of one glider behind the tug aircraft.

Note: Section 8.3 provides for separate and additional competencies to
be demonstrated for double towing to be included on a Glider Towing
permit.
ABNORMAL PROCEDURES
All the following procedures should be carried out in practice.
8.2.1
“Stop” signal on take-off run

Release glider, monitor mirrors and be acutely aware of possibility of
glider running into back of tug.
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8.2.2
Partial power failure
(a)
Tug on ground
Release glider. Keep tug moving if enough power is available to do so.
Monitor mirrors.
(b)
Tug airborne
Release glider, with due regard for strip available and/or the options for
the glider pilot, depending upon height and position. Land the tug in
whatever area has been pre-selected for the purpose.
Note: Procedure (a) should be followed if the tug pilot detects that the
glider's airbrakes have come open during the ground run.
8.2.3
Glider airbrakes (or tail-chute) open during climb

8.2.4
Glider flown out to left of tug. Acknowledgment given by tug pilot.
Glider and tug unable to release

8.2.7
Weigh up whether to release glider without warning or give a “wingwaggle”.
Glider unable to release

8.2.6
Consider whether to give rudder-waggle
Order to glider pilot to release

8.2.5
Assess height and position.
signal or get rid of glider.
Demonstration of this exercise is optional and will not be required for
issue of a Glider Towing Permit.
The “tug upset”

Definitely not to be practised!
However a tug pilot needs an
understanding of the dynamics of the upset manoeuvre and the
necessary preventative measures. See also Section 9.3 for further
information on tug upsets.
8.3
DOUBLE TOWING APPROVAL
8.3.1
Procedures
Requirements for double towing are as follows:
Adequate strip length, width and obstacle clearance.

Wingtip holders to be positioned at outer wings.
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
Forward signaller essential.

Water ballast must not be carried.
The short rope to be a minimum of 35 metres long and the long rope
minimum 65 metres long. Pilot on short rope should have had some prior
practice in flying on a shorter-than-normal rope. If possible, ropes should be
connected to the tug aircraft in such a way that, if jettisoned by the tug pilot,
both ropes will separate. The degree of difficulty in arranging this varies
with aircraft type and individual release installation.
Prior to take-off, if there is a light crosswind, the glider on the short rope
shall be placed on the upwind side of the tug, to minimise the chance of
ground-looping across the front of the glider on the long rope. If the
crosswind is strong, it is recommended that a double tow should not be
carried out.
The glider with the most efficient ground-braking system (skid or
wheelbrake) shall be placed on the long rope, and the more experienced
pilot shall fly this glider, in case the short rope breaks during the take-off run.
When the combination is airborne, both gliders shall fly directly behind the
tug, the glider on the short rope flying in high-tow, the glider on the long rope
in low-tow. The tug shall not turn until both gliders are settled in line-astern.
At the releasing stage, the glider in high tow on the short rope shall release
first and ensure that an immediate clearing turn is made.
In the event of a wave-off, the gliders release and break to the respective
sides from which they commenced the launch.
In the event of release failure in the first glider, the pilot shall fly the glider
out to the left (remaining in high-tow) to warn the tug pilot and the pilot of the
other glider. Upon receipt of acknowledgment from the tug pilot, the glider is
returned to the normal high-tow position, whereupon the glider on the long
rope releases and clears away. The tug pilot then releases the short-rope
glider from the tug end.
If the glider on the long rope has not released and cleared away within 10
seconds of the glider on the short rope returning to the high-tow position, the
tug pilot shall assume that it has also failed to release and shall release the
ropes at the tug end.
8.3.2
Pilot qualifications and operational requirements
Pilots wishing to undertake double towing must be in current flying practice
in glider-towing operations. The foregoing procedures must be strictly
adhered to and pilot must receive an adequate briefing from a CASA
delegate before undertaking double towing.
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8.3.5
Notification
Notification that a pilot is approved to carry out double towing as pilot in
command is by issue of the appropriate Permit by a CASA delegate.
8.4
OUTLANDING RETRIEVE APPROVAL
8.4.1
Prerequisites
A candidate for outlanding retrieve approval must have a minimum of 30
hours glider towing experience as a tug-pilot before undertaking an
assessment to qualify for outlanding retrieves. Note that the stipulated 30
hours should be regarded as a MINIMUM, as experience has shown that
considerably more than this is desirable, unless the candidate has special
experience relevant to the outlanding retrieve task, such as recent
experience as a cross-country glider pilot, with associated outlandings.
8.4.2
Ground preparation

Understanding of Civil Aviation Regulation (CAR) 92 and Civil Aviation
Advisory Publication (CAAP) 92-1, which explain the requirements for
use of an airfield which is not a public or military aerodrome. See
Section 12 of this manual for these documents.

Understanding of the reduced speed during cross-country towing (if
applicable) and its effect on fuel consumption, plus an understanding of
daylight/darkness graphs and the calculation of local last light.

Awareness of the effect of local weather conditions and surrounding
terrain on the time of onset of actual darkness, as opposed to “official
last light”.

Understanding of normal precautionary search procedures, particularly in
respect of assessment of suitability of paddocks with respect to size,
slope, surface, stock and surroundings, with special attention given to
SWER lines and their effect on selection of takeoff and approach paths.

If rope is attached to tug for the outbound trip, dropping of rope for
paddock landing. Assessment of adequate length for take-off, using all
applicable factors, including "P" Charts if available.

Practice in taking off without ground crew, using suitable agreed signals.
Assessment of length of crop/grass in paddock and an understanding
that the tug-pilot is not obliged to land in a paddock considered by that
pilot to be unsuitable.

Understanding that total fire bans preclude the possibility of an aerotow
retrieve. Understanding of responsibility to land owners.
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8.4.3. Notification
Notification of outlanding retrieve approval shall be by the issue by a CASA
delegate of a Glider Towing Permit including this privilege.
9.
EXPANDED GUIDELINES FOR GLIDER TOWING
PERMIT
This section is a “how to do it” expansion of the procedures in the previous
section.
9.1
NORMAL PROCEDURES
9.1.1
The purpose of an aerotow
The purpose of an aerotow is to provide the glider pilot with a safe and
efficient launch to his/her chosen height and position. Although this is not
difficult, there are many differences between flying around without a glider on
the back in comparison with the task of providing the best possible launch for
your trusting client.
The differences may be summarised as follows.
9.1.2. Daily inspection
The normal daily inspection is carried out on the tug aircraft in accordance
with Schedule 5 of the Civil Aviation Regulations 1988 (Amendment No 2,
August 1999), with the addition of the following items:1. Tow-release.
Inspect for integrity of attachment, cleanliness,
serviceability and proper connection from the cockpit.
Check
serviceability by attaching a rope with the approved rings fitted, and
releasing it under tension, for which an assistant is required. First tugpilot to fly the aircraft on any day must sign the Maintenance Release
that the release has been inspected in accordance with AD Supp. 8.
2. Tow-ropes. These should be of the correct length (55 metres for towing
a single glider) and must be fitted with approved rings. Ropes should not
be frayed and any doubtful sections replaced or, in the case of joins, respliced.
3. Weak-links. One of these must be fitted at the tug end. The maximum
breaking strength for tug aircraft is 450 kgs, except for the Pawnee 235,
which is 750 kgs.
4. Mirrors. It is a requirement (GFA Ops Reg 8.4.3) that at least one mirror
is fitted to a tug. It is more usual to have two. They may be mounted on
wing-struts or on the fuselage sides. It is normal practice to align one
mirror on the high-tow position and the other on the low-tow position.
Check them for cleanliness, broken glass and security of attachment.
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5. Cleanliness of transparencies.
Although important at any time,
cleanliness of the windscreen and side-windows is of paramount
importance for aerotowing. Scratches, bugs and oil-streaks play havoc
with detection of other aircraft. Make sure everything is absolutely as
clean as possible.
9.1.3
Performance of tug/glider combination
When a glider is hooked onto the back of a tug aircraft, the all-up weight of
the combination obviously increases. Gliders vary in weight from the
lightweight single-seaters of around 300 to 400 kgs (or even lighter) to single
or two-seat monsters of up to 750 kgs.
The higher all-up weight of the tug/glider combination means a considerably
longer ground-run than the basic aircraft. There is also a reduced climb-rate
to consider. The combination of the two results in a major reduction in
obstacle clearance, which must be taken into account on every launch.
All aircraft approved for glider-towing have Flight Manual supplements for
the purpose. Most tug aircraft have revised Performance Charts ("P" Charts)
for the glider-towing role incorporated into their supplements. See Section
12.1.
If the tug has a revised "P" Chart, it should be used to pre-plan the take-off.
If it has not got one (the Chipmunk and Tri-Pacer are two examples), follow
the guidelines in the Flight Manual supplement, which typically suggest that
the take-off distance to 50 feet without a glider on the back should be
factored by 1.5 when towing a single-seat glider and doubled for a twoseater.
Important note. When considering glider weight, what you see is not
necessarily what you get. High-performance gliders carry water-ballast in
their wings for enhancing their cross-country performance. Some of them
can carry more than 200 kgs of water, or the weight of two big persons.
Since there is no means of telling the difference between a "dry" and a "wet"
glider by its appearance (apart from a few gliders on which the wings droop
noticeably when they are ballasted), it is obviously important to check the
weight of the glider by asking the pilot before attempting to tow it.
9.1.4
Awareness of glider limitations
All gliders have a minimum speed for towing. This is usually governed by
the wing-loading. Very heavy gliders will need to be towed much faster than
lightly loaded gliders and tug-pilots need to get used to the range of
minimum speeds of the gliders they tow, and above all to ask if they don't
know.
Gliders also have a maximum speed for aerotowing. This is a structural
limitation established during certification and gliders must be kept below this
limit. This means another speed to check and memorise for each type.
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The most critical gliders in terms of maximum speed are some of the older
designs, where the tug may have to slow down considerably to prevent
overspeeding of the glider. This makes the tug more difficult to fly, the
margin above the stall reduced, control responses degraded and engine
cooling often suffering as well. These speed-limited gliders should not be
towed by inexperienced tug-pilots, as the operation needs a high degree of
skill and a broad background of glider-towing.
Although strictly more of a problem for a glider pilot than a tug pilot. some
gliders (e.g. Std Libelle, Hornet) suffer considerable speed errors due to the
rope occupying the same hole in the nose as the pitot head. Just keep it in
mind.
9.1.5
Glider airbrakes
Many power pilots will be unaware of the existence of airbrakes on gliders.
These devices, used to control the final approach to land, have a particular
trap which may catch a tug-pilot. In the closed position, airbrakes blend into
the wings, but they may not necessarily be locked in that position. There is a
very subtle difference in appearance between airbrakes which are closed
and flush, but not locked, and those which are locked properly in their correct
position for take-off. The learning tug-pilot would be wise to observe a
number of gliders and store this subtle difference away for future use.
If an aerotow commences, and the glider's airbrakes are closed but not
locked, they will probably suck slowly out and remain undetected by the
glider pilot. The effect of open airbrakes on the take-off and climb
performance of the combination is drastic and will completely compromise
the carefully-laid plans made before take-off. The tug-pilot should cultivate
the habit of checking for open airbrakes as soon as practicable during the
take-off.
9.1.6
Greater chance of engine failure in tugs
Although the evidence that tug engines are likely to fail more often than other
light aircraft is anecdotal rather than based on hard facts, they do lead quite
a hard life and there may possibly be an enhanced risk of failure. This could
arise for a number of reasons.
1. A large number of hot/cold cycles resulting from a full-throttle climb,
followed immediately by a partial-power descent. The climb in particular,
because it is often at less than the optimum climb speed for the type,
may result in much heat being generated and this may result in greater
wear and possible valve damage.
2. The use of Mogas (motor car gasoline) in some tug engines, with its
higher risk of vapour locking at high ambient temperatures.
3. The tendency of some pilots to skip pre-takeoff checks on busy days,
leading to running out of fuel.
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It may be of interest to note that, statistically, the biggest risk to a glider pilot
on aerotow is not a broken rope or an outright failure of the engine, but the
tug pilot allowing the engine to run out of fuel.
The possibility of an enhanced risk of engine failure should encourage tugpilots to have a sharpened awareness of emergency landing options on the
take-off path.
9.1.7
Minimum fuel for tow
Tug pilots must be acutely aware of the high rate of fuel consumption during
aerotowing, with the engine operating at full or very high power settings
during the climb. A pilot used to a moderate fuel consumption at cruise
settings may need some time to become accustomed to this.
The problem is worsened by the poor design of some fuel gauges. Some
versions of the Pawnee, for example, have a fuel gauge which becomes
opaque with age and almost impossible to read. There are similar traps in
other tug aircraft, for example some taildraggers have fuel gauges which
differ markedly in their readings depending on whether the aircraft is in flight
or in the tail-down attitude on the ground. Pilots should keep track of how
many tows they have done and refuel early rather than late. Trying to run
the tank down as dry as you can before refuelling, even in these days of no
compulsion to carry 45 minutes reserve fuel, is the very opposite of good
airmanship. On aircraft which have recording tachometers (most American
machines), keeping track of tacho time is a useful aid to fuel management.
Incredible as it may sound, there has been a case of a pilot taking off
knowing the tug was short of fuel, but offering to tow a glider on the basis
that they might not reach the top of the tow. They didn't, and the result was
a completely unnecessary outlanding for the tug. This behaviour on the part
of an experienced tug pilot was so stupid as to be almost beyond belief, but
it happened. No marks to the glider pilot either. He should have told the tug
pilot what to do with his almost empty tug.
9.1.8
Pre take-off checks
Normal pre take-off checks apply to tug aircraft. There is no reason not to
do such a check before every tow. There is ample evidence that many pilots
do not do a satisfactory check before every take-off, as far more tug aircraft
run out of fuel in flight than any other light aircraft. Before every flight, make
a habit of ensuring that you know the location of the tow-release and its
direction of operation. You may need it in a hurry.
The repetitive nature of glider towing tends to result in skimped checks or no
checks at all. It might be thought that a pilot doing repeated tows has his/her
finger on the pulse and is in a good position to keep track of fuel state, etc.
The evidence suggests the opposite; that such pilots do in fact become
complacent and are more likely to get caught out than pilots who are
conscientious about checks on every flight.
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A further thought is that fuel exhaustion often occurs shortly after a running
change, where the replacement pilot has taken over an almost empty
aircraft, the "keeping track" chain is broken and the old pilot does not pay the
new pilot the courtesy of mentioning the low fuel state. If the new pilot then
does not carry out a proper check, fuel exhaustion is inevitable.
The only answer to such problems is a proper check before each flight. It
might seem like a nuisance, but the alternative is worse. During the check
turn on any external lights that will be useful for making you easier to see.
9.1.9
Ground signals
There are usually two signallers for aerotowing, one at the wingtip of the
glider and the other positioned forward of the tug and to one side. Some
clubs dispense with a forward signaller, but this is not a satisfactory practice
because it forces the tug pilot to either look in the mirror or backwards over
the shoulder during the initial part of the take-off. Looking at the very small
image in the mirror may cause the tug pilot to miss something which might
endanger the take-off; looking backwards is awkward and in any case
cannot be done in some tugs because they have no visibility in that direction.
It could also be argued, quite reasonably, that asking a pilot to look
backwards at all during a take-off is an unacceptable practice.
It is up to the tug pilot to accept or reject a take-off without a forward
signaller. However, it is strongly recommended that the culture of a forward
signaller be encouraged and tug pilots should ideally regard the lack of such
a signaller as a "no go" item for an aerotow take-off.
There are three signals from the ground crew to the tug pilot, as follows:-
9.1.9.1 Take up slack
This is an underarm wave signal given by the wingtip holder and repeated by
the forward signaller. The tug pilot should ignore a take up slack signal
given by anyone else.
On receipt of this signal, the tug pilot should taxi the tug slowly forward until
the slack is taken up. Taxying too fast runs the risk of jerking the glider
forward when the slack is taken up. If this occurs, there is a strong
possibility of the glider running over the rope, which may then wrap itself
around some part of the glider's undercarriage or airframe. This is clearly
undesirable, so take it easy when taking up slack and keep your eye on the
mirror(s).
9.1.9.2 All out
This signal, known in some regions as "full power", consists of an overarm
wave. It means that all the slack is out of the rope and the take-off should
proceed. Again, the tug pilot should ignore an “all out” signal given by
anyone other than the wingtip holder or the forward signaller.
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9.1.9.3 Stop
Self-explanatory. This signal, consisting of one or both arms held stationary
above the head, may be given by anyone at the launch point.
9.1.10 Take-off technique
When the "all out" signal has been given, open the throttle smoothly to full
power, keeping in mind any "idle to full throttle, 2 seconds minimum"
limitation that may apply.
At this point you will find that you have one additional job to do which you
never had before. You should keep the forward signaller in view, even if it is
just in the corner of your eye, for as long as possible, just to make sure you
don't get a stop signal. If you do, there are specific actions to take, which will
be covered under “abnormal procedures”.
Once you have full power applied, you will find that acceleration is much less
than you are used to. This is especially true if you are towing a glider with a
nose skid, where the ground-drag is very high.
Keeping straight, even in a taildragger, is easier than it is without a glider on
the back during the initial stages. This is because of the pull of the rope.
However, the pull of the rope also has a tendency to lift the tail of a
taildragger. If you have cultivated a habit in non-towing operations of using a
lot of forward stick to lift the tail of the aircraft, you may find that you get a bit
of over-rotation at this point and will need to move the stick back a bit.
You are vulnerable if the rope breaks at this point, as the tail will be up, the
stick forward and the tug will rotate smartly nose-down when the rope-break
occurs. The correct technique when towing with a taildragger is to start the
take-off run with the stick aft of neutral, allowing the rope to level the tug,
which it will naturally do as the take-off progresses.
Separation technique - gliders with light wing-loading
A glider with a light wing-loading (say between 20 and 30 kgs/sq. metre) will
usually leave the ground before the tug. The pilot will position it a few feet
above the ground and do his/her best to hold that position until you lift off.
You will find that you will have to make a positive rotation into the take-off
attitude and the tug will then leave the ground and start its climb.
Some pilots then level off and let the speed build up to the full value they are
going to use for the tow. This is not a good technique for this category of
glider, because it makes life unnecessarily hard for the glider pilot. The best
technique for the “average” club glider is to let a bit of speed build up, then
let the combination climb, even if you have not yet achieved the eventual
climb speed. You can then refine the nose attitude as you climb away, very
gently accelerating to your full climb speed a few seconds later.
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The advantage of doing it this way is that it does not overspeed the glider
and creates a bit of space under the combination, a real advantage for the
glider pilot, especially if it is an instructional flight. There is no disadvantage
for the tug, because almost all the tugs have a take-off safety speed at or
below the combination's climb speed.
There is a further advantage in letting the tug climb early in the take-off if
there is a wind-gradient. If the tug is held down and then rotated into the
climb attitude after the full value of speed has built up, the attitude change is
greatly exaggerated by the increase in wind as height is gained. The tug
pilot finds himself pulling back further and further and the glider pilot is barely
able to cope with the rapidly changing circumstances. This is illustrated in
the diagram below, courtesy of Fred Foord of the Adelaide Soaring Club,
who experienced the phenomenon at first hand and eloquently describes it,
as he puts it, “with a little help from Pythagoras”. The climb angle, 36º, is
somewhat exaggerated, but serves to illustrate the principle very well
because it forms the hypotenuse of a 3:4:5 triangle.
The speed immediately after separation of both aircraft is assumed to be 61
knots (the maximum aerotow speed of the Kingfisher the pilot was flying at
the time). When the tug climbs along the hypotenuse of the triangle, as
illustrated, its speed over the ground falls to about 49 knots, a difference of
11 knots. It will be apparent that if this occurs abruptly (which is what
occurred), a slack rope is inevitable and the rope will probably break when
the slack comes out. Either that, or the glider’s nose will be pulled up
uncontrollably. The glider-pilot has no choice but to release. Figures for the
shortfall in speed at the tug end at other climb angles are - 2 knots at 15º,
3.5 knots at 20º, 5.7 knots at 25º and just over 8 knots at 30º.
Separation technique - gliders with heavy wing-loading
When towing gliders with a heavy wing-loading (from 30 kgs/sq. metre to a
typical value of over 50 kgs/sq. metre for a modern standard class glider full
of water), the opposite problem will occur. Heavy gliders may not leave the
ground before the tug - in fact it is reasonably common to see a heavy glider
still on the ground with the tug airborne. If the tug climbs too early in this
case, the glider will either not have flying speed and will have to release
before it collides with the upwind fence, or it may have marginal flying speed
and get dragged into the air barely above its stall speed and virtually
uncontrollable. Neither of these options is attractive.
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The solution is to keep the tug on or close to the ground until the known
climb speed has been achieved, then allow the tug to separate and enter the
initial climb with plenty of speed to give the glider pilot good control. A
marginal speed for a heavy glider is really hazardous and can easily result in
the death or serious injury of the glider pilot in the event of a low-level ropebreak or the pilot having to release because of inability to control the glider.
From the foregoing descriptions of the two extremes of take-off technique, it
be obvious that the tug-pilot must know the characteristics of the glider about
to be towed, especially its weight. Once this is known, the exact technique
to be used may be pre-planned and put into practice. It is necessary to go
through this exercise prior to EVERY tow.
After separation and entering the initial climb, the glider will be initially in the
"high-tow" position, just above the tug's slipstream. However, fairly early in
the climb, the glider will probably move down and settle in the "low-tow"
position below the slipstream. The tug pilot will feel the trim-changes
occurring as the glider changes position and will probably need to re-trim the
tug when the glider has settled down.
The glider pilot may choose to remain in high tow throughout the entire tow.
This will almost certainly be the case if the glider pilot is a visitor from
overseas. Do not assume anything - wait to see which position the glider
pilot selects.
During the take-off, the tug-pilot needs to monitor options for any emergency
that may occur and choose a take-off path that takes these into account.
While abiding by the legal requirement to climb straight ahead to 500 feet
AGL, the pilot may need to make slight deviations to maximise safety for the
combination during the take-off.
9.1.11 The steady climb
The primary reference for maintaining a steady climb is nose attitude. As in
a glider, any tendency to over-concentrate on the airspeed indicator will
result in a wavering nose-attitude. This makes life very difficult for the glider
pilot.
The ASI should be used only as a trend monitor during the climb. Only if a
reasonably long-term trend indicates a deviation from the chosen climb
speed should the nose attitude be altered, and even then with care.
Care should be taken to ensure that the slip/skid ball is exactly in the middle
when towing a glider. This not only optimises the climb rate (an aircraft
flying sideways is not very efficient), but it makes it easier for a glider pilot to
position the glider accurately behind the tug. You would be surprised at how
mad glider pilots get trying to line up on an aircraft which is flying slightly
sideways through the air.
Make all turns gentle, especially with a training glider on the back.
instructor will thank you for steep turns on tow.
No
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Do not assume that the glider pilot you are towing is very skilled. Everybody
has to learn, and quite a high proportion of glider tows are training flights.
Be prepared to work hard to maintain a steady platform for the glider while it
swings around on the back trying to hold position - this is where doing some
tows at the glider end yourself gives you some empathy with the glider pilot’s
problems.
Carefully monitor engine instruments when aerotowing, especially oil
temperature, oil pressure and (if fitted) cylinder-head temperature. If cowlflaps are fitted, it may be necessary to adjust these during the climb,
although they will usually be left fully open. Unless the engine has a time
limitation on full power, the throttle is usually left fully open on the climb.
The mixture should not be weakened unless density altitude problems cause
rough running.
Do not climb on a constant heading for long periods of time. All tug aircraft
have blind spots and it is essential to ensure that the airspace you are about
to occupy is clear. Remember that targets which are stationary in the
windscreen constitute the biggest collision risk and perversely are the most
difficult to detect. You will need to find a sensible compromise between a
good search pattern to eliminate stationary targets as much as possible,
while still retaining a good steady platform that a trainee glider-pilot will be
able to follow without undue difficulty.
As a general principle, tow into wind. A glider's range if towed downwind is,
for the purpose of returning to the airfield, only one-third of its range if you
towed it into wind. Only tow downwind (or a long way crosswind) if you are
asked to, or if controlled airspace or other reasons compel you to.
If cumulus clouds are present, read the sky and plan on maximum use of lift
during the climb. When descending, plan on using the sink to assist the
descent. If it is a “blue” day, with no clouds, work out as soon as you can
where the lift is, and use it to maximum effect during the climb. Ditto with
sink for the descent.
Avoid rain and close proximity to cloud.
Gaggling gliders can be
troublesome, but in competitions is an occupational hazard. When towing in
competitions, exercise extreme care near gaggling gliders.
Monitor the mirror(s). The ideal mirror installation for a tug is either one
large panoramic, slightly convex mirror which covers both high and low
towing positions (at the expense of rather high drag), or two smaller mirrors,
one aimed at high tow, the other at low tow. These should preferably be
adjustable from inside the cockpit.
9.1.12 High-tow and low-tow
An aircraft in flight generates a “slipstream” behind it. This is a region of
turbulent air, originating mainly from large vortices streaming from the
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wingtips, with small amounts of other turbulence such as propeller wash
thrown in for good measure.
A glider pilot may choose to fly either above or below this turbulent
slipstream. As already mentioned, Australia tends to favour the “low-tow”
position. Other countries prefer “high-tow”.
Low-tow
With a glider in low-tow, below the slipstream, the combination tends to be a
little more stable and tug pilots have less difficulty in maintaining a steady
platform for the glider pilot to follow.
High-tow
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In high-tow, above the slipstream, the combination feels a little more “lively”
as far as fore-and-aft trim is concerned and tug pilots need to concentrate a
little harder. The difference is not large and tug pilots should have no
difficulty in maintaining a steady platform whichever position the glider pilot
chooses. Note that high-tow is, by definition, above the slipstream, not
above the tug.
There is one important difference between low-tow and high-tow and this
becomes apparent if a glider gets out of position vertically. In low-tow a
glider can get very low and still not cause great difficulty for the tug pilot in
controlling his aircraft. Furthermore, out-of-trim forces tend to change at a
slow enough pace that the tug pilot has ample time to release the glider if
there is any fear that the limits of control might be reached.
In high-tow, things happen more rapidly and the tug pilot will have to react
rather more quickly to a glider going too high. If an excessively high glider is
not released without undue delay, there is a risk of being pulled out of
control. See Section 9.3 “The tug upset”.
Tug pilots need to be trained to tow gliders in both high and low-tow and to
experience a glider transitioning between the two positions. To avoid
subjective judgements about high-tow and low-tow, the reference for
establishing towing position is always the SLIPSTREAM.
9.1.13 “Boxing the slipstream”
Glider pilots sometimes carry out an exercise known as “boxing the
slipstream”. It is a good test of a glider pilot’s aerotowing skill and the
exercise is carried out by flying the glider in a box pattern around the
slipstream, initially moving to the right, still in low-tow, then moving up into
high-tow, still out to the right. The glider then slowly crosses from right to left
in the high-tow position, then descends to the low-tow position while still out
to the left. Finally the glider returns to line-astern in the low-tow position and
the exercise is over.
The objective is for the glider to carry out this exercise without contacting the
slipstream and the tug-pilot’s job is to maintain a constant attitude and
heading during this exercise. This means constantly changing control inputs
as the glider changes position. Some of these control inputs may be quite
large. The most critical point is the transition from right to left in high-tow,
where a glider pilot sometimes moves too quickly and gets a lot of slack in
the rope. This may or may not be a problem, depending on where the rope
goes in its travels!
As in all phases of an aerotow, if you feel you are being taken close to the
limits of control or you have no idea where the glider has gone, get rid of it.
Do this BEFORE you lose control altogether.
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9.1.14 Releasing from tow
Ensure the rope has released before beginning descent. Do not begin
descent until you have CONFIRMED VISUALLY that the rope has been
released from the glider. If the mirrors are not adequate for this purpose,
you must turn round in the seat to make sure it is clear. NEVER assume
that a jerk or twang in the rope is the glider releasing and NEVER rely on a
radio call, especially if it is a “blind” (no callsign) call.
9.1.15 The descent
When certain that the glider has gone and that the airspace you are about to
occupy is clear, begin the descent. Don’t fiddle around maintaining almost
level flight while you gingerly reduce power - you will take all day to get
down. Start closing the throttle smoothly and get the aircraft descending.
Use carby heat as required. Be careful not to accelerate too quickly in the
early stages of the descent. Interchange throttle closure with airspeed to
achieve a moderate initial descent rate, keeping in mind that too much speed
is a bigger factor in cylinder cracking than closing the throttle too far. Keep
all throttle movements smooth and power reductions gradual.
Note that, although the glider will always turn to its right after release, there
is no need for the tug to turn immediately. Clear the aircraft’s blind spots
before manoeuvring. Once again, remember the “stationary target” problem.
NO AEROBATIC DEPARTURES AFTER RELEASE. Any pilot who indulges
in these antics is a hazard to everyone else in the vicinity and such
behaviour will usually result in a club showing the pilot the door.
Plan the descent profile, using any sink you can find, regularly clearing the
aircraft’s blind spots, avoiding other traffic and generally not making a
nuisance of yourself. Remember the rope!
Do a “head-count” of known traffic during the descent. Make maximum use
of aircraft shadows to locate them. However, even when you are certain you
have accounted for all known traffic, do not relax. There may be visiting
aircraft or gliders and it is well-known that it’s the one you don’t see that gets
you! Know your airfield procedures, especially if you are in a CTAF or
CTAF<R>, operate in accordance with them and remember that you are
legally obliged to give way to gliders. At circuit entry, make any applicable
radio calls. As a general principle, be where other airspace users will expect
you to be.
If you know there is a glider there, but you can’t see it, there is a school of
thought which recommends placing the tug in a position where a glider
cannot normally go - low and a long way away. If you do this, you may be
able to pick out the missing glider against the sky. However, your own
aircraft will not be as easy to see and you will probably violate the principle
of being where you are expected to be.
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Continue monitoring the engine during the descent, planning to be at your
approach power settings by the time you are on base leg. Aim to enter base
leg not lower than 500 feet AGL. Do not cut gliders off, remember they have
no engine to re-position themselves. Do not cut off any other powered traffic
committed to landing. Take account of any built-up areas.
Carry out pre-landing checks, being especially meticulous about fuel.
9.1.16 Landing
Enter base leg and final. Keep clearing the aircraft’s blind-spots. If you have
been using carby heat, select cold air on final approach in preparation for a
possible go-around. Open the cowl-flaps for the same reason. Remember
the rope and give yourself plenty of clearance over obstacles. Approach
high and land long in preference to cutting it fine over people or objects on
the ground. A 55 metre rope hangs about 40 feet below a tug at approach
speeds. NEVER land over the top of parked gliders. Remember that tugs
have no exemption from the requirement to have the wings level on a
stabilised final approach for a minimum distance of 500 metres.
Most tugs carry out glide or near-glide approaches. A particular hazard
associated with this practice is the possibility of descending on top of
another aircraft or glider which has remained in the tug pilot’s blind spot
throughout the approach. A number of collisions and near-collisions have
occurred from this cause. Check very carefully during the final turn that you
are not about to become involved in one of these conflicts, again making
maximum use of all cues available to you. Shadows are especially effective
and valuable at low level. Remember that, even if you do avoid a collision
by last-minute evasive action, your rope is still a hazard.
9.1.17 Baulked approaches and go-arounds
On every approach, be prepared to go around. You never know when
someone will walk, or even drive, out in front of you to retrieve a parked
glider. Remember the rope!
9.1.18 If in doubt, drop the rope
When the rope is dropped, it loses forward impetus very quickly and ends up
dropping almost vertically to the ground. In any case, even if it still has some
forward motion, it will probably not do a great deal of harm as long as it is not
still attached to the tug aircraft. If you have any doubt about obstacle
clearance, whether it be buildings, vehicles, parked or taxying aircraft or
people (especially people), don’t hesitate to drop the rope. It is inexcusable,
and may prove fatal, to drag a rope through a gathering of people.
The same applies to a go-around. Much better to drop the rope and
eliminate that particular worry than to risk hitting something underneath your
projected overshoot path.
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9.1.19 Approaching too low
Hitting the fence with the rope is unfortunately very common, usually
resulting in loss of the rings. This in turn usually results in you being invited
to lead an “emu bob” to find them. Occasional genuine misjudgements do
occur, but many cases of hitting fences with ropes are the result of pilots
deliberately cutting things too fine over the fence in an attempt to land as
short as possible to reduce the need for taxying.
You need to ask yourself whether such a technique is really worth-while.
Hitting a fence with the rope is one thing; hitting someone who is standing
near the fence, or a vehicle on a road, is inexcusable.
It is much better to accept the need to taxi back to the launch point each time
than to cut things finer and finer until eventually a completely unnecessary
accident occurs and somebody gets hurt.
9.1.20 Cruising on tow
Most glider towing consists of a climb, dropping the glider, then a descent.
Occasionally there will be a need to actually cruise the combination in level
flight. This may occur during an aerotow ferry flight or in the training for such
a flight. The glider’s maximum aerotow speed is essential information for the
tug-pilot to have before take-off.
The presence of a glider on the back makes quite a difference to the
technique you will need to use in certain parts of the flight. For example the
usual “APT” (Attitude, Power, Trim) technique for transitioning from climb to
cruise may be used, but if so, it must be smoothed out and spread over a
much longer time than usual. Otherwise you will risk getting a lot of slack in
the rope and may even break it.
A better technique in this phase of flight is to start reducing power, still in the
climb attitude, as you approach your cruise altitude. Know your aircraft,
especially its power/weight ratio, and fly it in such a way that you start
reducing power while still in the climb. The rate of climb falls off and the
nose should be very gently lowered to keep the speed virtually constant as
the power is reduced. As the climb-rate approaches zero, the nose should
be at or very close to the cruise attitude and the speed will build up very
slowly. It won’t get away from you, because the power has already been
reduced. The attitude change and rate of speed-change during this
manoeuvre will be gradual enough for the glider pilot to adapt to both without
getting a lot of slack in the rope. When you are established in level flight and
have refined the power setting to get the cruise speed you want, trim the
aircraft out.
When established in the cruise, with the glider settled in its towing position, it
will feel different from the climb. The drag of a modern single-seat glider is
very low, in the order of 15 to 25 kgs in level flights at 70 knots or so, and
this does not provide much pull on the rope. This is not a problem if
conditions are smooth and the glider pilot is competent. However, it can be
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a different story when conditions are turbulent and/or the glider pilot is a bit
behind the eight-ball.
In cruise flight do not relax.
Monitor the mirrors continuously and
concentrate on accurate attitude control. You can expect the occasional tailwag, as a bit of slack develops in the rope and the glider pilot takes action to
correct it. This will be virtually constant if the air is rough. As is the case in
any other phase of aerotow operations, if the antics of the glider on the back
are taking you to the limits of control, you are entitled to get rid of it.
During cruise flight, especially if the air is rough, the glider pilot may find it
necessary to use small amounts of airbrake to keep the rope tight. This will
probably not be a permanent condition, but it may occur at intervals during
the flight. Unlike normal aerotow launching, this is quite normal and you
should not worry about it.
Also unlike ordinary aerotow launching, the glider pilot on a ferry flight will
not thank you for seeking out thermals. Try to find the smoothest air you
can, in the interests of comfort and safety. If you think it is hard controlling
the tug when cruising in rough air, try it on the other end of the rope
sometime!
9.1.21 Descending on tow
This is not normally required on a ferry flight, as the glider will usually
release and make its own way into the circuit, leaving the tug to do the
same. However, a descent on tow may be required from time to time, for
example to remain outside of controlled airspace. It is also a post-solo
training requirement for glider-pilots.
When transitioning from cruise flight into a descent, the normal APT principle
does not work at all. If the nose is lowered with cruise power still applied,
the speed gets rapidly out of hand and this makes things impossible for the
glider pilot. Once again start reducing power very gently at a constant
attitude, then allow the nose to fall slowly so that the descent develops
slowly without a great build-up of speed. Refine your power-setting and
nose attitude as the descent settles down, monitoring the mirrors for the
glider pilot’s well-being. Trim when ready
It is almost impossible to start a descent without getting some slack in the
rope, especially in rough air. You can be sure that the glider pilot will be
monitoring this as closely as you, and the glider’s airbrakes will almost
certainly be used to keep this under control. Watch the glider carefully in
your mirrors and if it needs to use full airbrake to keep the rope tight,
moderate your descent until the airbrakes retract a little. You now know that
the glider pilot has a little more drag up his sleeve if he should need it.
Continue the descent in this fashion until the glider releases.
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9.1.22 The Non-Manoeuvring Area (NMA)
Under certain circumstances, such as a low-powered tug towing a glider off
a fairly short strip in a light wind, it is possible to get into a situation where, if
the rope should break or the tug wave the glider off, the glider would be too
high to land ahead within the available strip and too low to safely turn back to
the strip. This is known as the Non-Manoeuvring Area (NMA).
The NMA does not apply directly to tugs, as all power pilots know that
engine failure is possible at any time and they plan their options accordingly.
These options are often not very attractive and it is true to say that any pilot
operating out of a capital city GAAP aerodrome effectively spends quite a lot
of time in an NMA. However we now have a glider to consider and the effect
of an NMA on a tug-pilot is to focus attention on the glider’s situation.
If a rope should break, for example, the tug is completely unaffected. It is a
different story for the glider. The tug pilot should plan the take-off path such
that, even though the glider may be in a non-manoeuvring area, the best
possible options are available to it, preferably a straightforward outlanding in
a paddock. If this is not possible, at least track over such terrain that the
glider will be able to achieve a survivable landing, even though it might be
damaged. This is a new concept for a power pilot and is a good example of
the effect of having to think for two people at the same time. It is the tugpilot’s duty to do the best thing by the glider pilot at all times, at the same
time not compromising his/her own safety.
9.1.23 Some suggested towing patterns
The towing patterns suggested here, courtesy of the Waikerie Gliding Club’s
towing notes, are just a few of many possible variations. If the wind is very
light, the tug may circle, but the combination should never be taken
downwind of the mid-point of the strip, except by request of the glider-pilot.
In strong winds it may be possible with some tugs to tow straight upwind
without making any turns except clearing turns to compensate for aircraft
blind spots.
At all times, keep a sharp lookout, continually clear the aircraft’s blind spots
and if possible avoid those parts of the sky in which you know traffic will
congregate, e.g. circuit joining areas.
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9.2
ABNORMAL PROCEDURES
Practical coverage of items 9.2.1 to 9.2.7 is mandatory.
optional.
9.2.1
9.2.1.1
Item 9.2.8 is
“Stop” signal during take-off run
Early in the take-off run
Release glider. Monitor mirrors and be acutely aware of possibility of glider
running into the back of the tug. Keep the tug moving, avoiding sudden
braking.
There is no particular reason to turn after you have released the glider, at
least until you are sure the glider has stopped. Get well clear, THEN turn.
9.2.1.2
Later in the take-off run
Release glider. If you have a fair bit of speed on, it is probably better to
continue your take-off and thereby ensure that you are well out of the glider’s
way. Carry out a short circuit and try again.
At all times think ahead, assume you are going to get a stop signal on each
and every take-off and be prepared for it.
9.2.2
9.2.2.1
Engine failure
Tug on ground
In the case of partial engine failure, do not assume the engine will “come
good”, even if you think it is just a vapour lock and will clear itself. Pilots who
make assumptions get caught out. Release the glider. Apply the same
philosophy and pilot actions as for a stop signal early in the take-off run,
except that it may be more difficult to keep moving if your engine is on the
blink. Use whatever power you have to open up the distance between you
and the glider. Don’t be tempted to take-off with a suspect engine. If the
engine failure is complete, just get out of the way as best you can, turning in
the direction most appropriate in the prevailing conditions.
9.2.2.2
Tug airborne
Treat partial and complete engine failure as identical occurrences and
release the glider, with due regard for strip available and/or the options for
the glider pilot, depending on height and position. As there are thousands of
permutations of height, position and landable ground, no hard and fast rules
are possible. Be imaginative and plan your take-off path to maximise
options for both aircraft, although the glider will be better off than the tug,
having better performance to find a spot to land and no fuel on board to
worry about.
If you have time, go through normal engine-failure drills. If no joy, land the
tug in whatever area has been preselected for the purpose. If you haven’t
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preselected a possible landing area, there’s a lesson there and you probably
will the next time you fly.
9.2.3
Glider’s airbrakes coming open on ground-run
This is more common than you may want to believe. It has already been
pointed out that airbrakes may appear to be locked when in fact they are not.
This is one of the major reasons for having a good mirror installation on the
tug and monitoring it during the take-off (however, not at the expense of
keeping control of the tug).
If the airbrakes come open on the ground-run, get rid of the glider and
decide whether it best for you to take-off or continue a fast taxi down the field
until clear.
9.2.4
Glider’s airbrakes coming open during climb
Assess height and position. If the combination is in danger (e.g. sinking),
release glider.
If combination is not in danger, give “rudder waggle” signal. If possible,
signal to be given at sufficient height to allow for the glider pilot possibly
misinterpreting the signal and releasing inadvertently.
Notes:
9.2.5
1.
With a glider’s airbrakes open, a Pawnee 235 or similar tug will
probably be able to continue climbing at about ¼ to ½ its normal climb
rate in still air, something of the order of 300 to 400 feet/min. This
gives the tug-pilot the option of getting the glider to a safe height and
position before giving the rudder-waggle, thus minimising the effect of a
misinterpretation. This option may not available to low-powered tugs
(say, under 180 hp), most of which cannot climb at all if the glider’s
airbrakes come out.
2.
The rudder should be waggled at such a frequency that yawing of the
tug does not result. The signal is a rudder waggle, not an aircraft yaw.
3.
Some gliders have a tail-parachute to augment their rather weak
airbrakes. These have been known to deploy inadvertently on tow, so
watch out for this problem too.
Other reasons for poor rate of climb
The rudder waggle signal really means “rate of climb not normal, I have
checked my aircraft, please check yours”. The usual cause is accidental
deployment of the glider’s airbrakes, with the very occasional tail-chute for
good measure.
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There can be other explanations for a poor climb rate and the tug-pilot
should be aware of them. They include:-
9.2.6
1.
Strong sink. Combined with a low-powered tug and a heavy glider,
strong sink can play havoc with the climb-rate. This is where the ability
to read the sky pays dividends, although it is often difficult to do this on
a “blue” day with no cumulus clouds to mark the thermals. Deciding
whether the climb-rate is not normal because of strong sink, or whether
there is something wrong with the tug, is one of the more awkward
decisions a tug-pilot will have to make from time to time, but it does
come with experience.
2.
Wrong propeller setting. This is unlikely, but it can happen and a pilot is
particularly susceptible to it if he/she has fallen into the trap of skimping
checks.
3.
Wrong flap setting, carby-air selected to hot, or only one magneto
switched on. These three problems, all of which have featured from
time to time in incidents around Australia, can usually be traced back to
the same category as 2 above.
Order to glider pilot to release - the “wave-off” signal
This consists of a rhythmic rocking of the wings from side to side. A
waggling of the ailerons is not sufficient, as such waggling often occurs in
turbulence. The signal should be given as a clear and properly coordinated
rocking of the wings, with no residual adverse yaw.
If no response, release the glider without any further delay.
Note that the signal should only be given if there is no immediate danger to
the combination, for example if the engine is starting to overheat and you
would like to get rid of the glider as a precaution. If the tug suffers a sudden
and/or catastrophic failure, make no attempt to signal; you are quite entitled
to release the glider without warning.
Important note on the wave-off signal. There is no such thing as a
“practice” wave-off. Every one of them is for real and must be obeyed by the
glider pilot; otherwise they will be jettisoned without further ado.
9.2.7
If the glider is unable to release, it is flown out to the left of the tug and the
glider pilot will hold it in that position until the tug-pilot acknowledges its
predicament by a wave of the hand. When the glider pilot receives the
acknowledgment, the glider is returned to the line-astern low-tow position,
and then climbed into high-tow, just above the slipstream. At this point, the
tug-pilot will fly towards the airfield and when the glider is within safe gliding
distance, release the rope at the tug end.
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When the glider pilot flies out to the left, the tug-pilot must resist any
tendency for the tug to be turned by the glider. It may take a considerable
force on the rudder pedals to keep the tug flying straight ahead with the
glider in formation out to the left. This force MUST be applied to keep the
tug straight, as any tendency to allow the tug to turn prevents the glider from
ever getting into its intended position. This drives glider pilots crazy and
defeats the object of the exercise.
9.2.8
Double-release failure - landing on tow (optional - not mandatory for Permit)
This procedure has its origins in failure to release the rope from either end.
Such an occurrence may be considered a rather long shot, but landing on
tow also happens to be an effective and “no sweat” training exercise,
valuable as a confidence-builder.
If you want to do it, here’s how. Having got the whole combination
comfortably descending in accordance with the procedure outlined earlier,
the next task is to get it all safely on the ground, still tied together. Although
this looks and sounds difficult, it is not so in practice.
The only requirement is that the glider remains in the low-tow position
throughout. The exercise is considerably more difficult in high-tow. The
stabilised descent continues, the glider maintaining low-tow and keeping the
rope just tight by use of partial airbrake. This is much easier for the gliderpilot if the tug-pilot does a wide, spacious circuit and avoids steep descents.
When the tug enters the base leg and starts gradually reducing power for the
approach, the glider pilot should go to full airbrake and/or flap as applicable.
This gives the tug-pilot a measure of the maximum drag which can be
exerted by the glider and enables the power to be adjusted accordingly. The
tug’s flap setting will be decided upon and selected at this stage and the
combination stabilised for the final approach.
On final, choose an aiming point well beyond the usual spot, as the glider on
the back dictates the necessary clearance over obstacles. When this is
done, go ahead and land normally. The glider will probably touch down a
little before the tug, as it is quite a lot lower. You can expect to pull just a
little bit harder than normal at the flare, as the glider is tending to keep the
tail up at this point. Keep a trickle of power on and don’t attempt any finesse
during the landing, a good basic arrival is all you need. The rope will tend to
hold you straight.
When you have touched down, DO NOT USE THE BRAKES. Let the glider
slow the combination down, by using its wheelbrake or skid. Monitor the
mirrors and be prepared to add a bit of power if the glider appears to be
catching you up. Some gliders are not very impressive in the wheelbrake
department. Be especially alert in crosswinds. Don’t relax until the whole
combination has been brought safely to a stop.
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9.3
THE “TUG UPSET”
This is an abnormal occurrence which warrants special consideration. Upset
occurrences are invariably serious and have sometimes proved to be fatal.
The problem occurs when the glider is allowed to get so high behind the tug
that the tug-pilot is unable to prevent the aircraft’s tail from being lifted. The
glider accelerates upward in a “slingshot” manoeuvre, tipping the tug nosedown and robbing it of its speed, thereby leaving the tug-pilot powerless to
prevent the aircraft entering a vertical dive. Refer to the diagram below,
reproduced with acknowledgement to the British Gliding Association.
There are a few things to keep in mind about the tug upset.
1.
When it happens, it happens faster than you would ever believe and it
takes a minimum of 800 feet to recover the tug to level flight.
2.
Under no circumstances should it ever be practised.
3.
The chances of a tug upset occurring are considerably reduced if the
minimum rope length is strictly adhered to. The shorter the rope, the
less TIME the tug-pilot has to get rid of the glider in an upset situation.
It does not take much shortening of the rope for this time-compression
to become critical.
4.
If the tug-pilot knows or suspects that a tug upset manoeuvre is
developing, (e.g. stick coming back continuously until it reaches a point
where it does not appear to be having any effect), RELEASE THE
GLIDER IMMEDIATELY. Release it before it gets to that stage if you
are in any doubt.
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CHECKLIST OF DO’S AND DON’TS FOR TUG PILOTS
DO ensure you know the speed limitations of the glider you are towing and
check whether it is carrying water-ballast
DO ensure you do a proper cockpit check before each take-off and landing
DO take up slack slowly to avoid overruns and monitor the signaller and the
mirrors during take-off
DO open the throttle smoothly when applying full power
DO be prepared to release the glider if circumstances dictate
DO follow the most landable terrain on initial climb and avoid noise-sensitive
areas if possible
DO tow into wind, as far as practicable
DO use moderate bank angles in turns when towing training gliders
DO make maximum use of lift during the climb, and sink during the descent
DO maintain a very careful lookout and be sure to regularly clear all blind
spots
DO close the throttle slowly and smoothly when beginning descent
DO continue to clear all blindspots regularly during descent
DO join the circuit in a legal and predictable fashion
DON’T tow downwind, unless terrain or controlled airspace dictate, or the
glider pilot specifically requests it
DON’T tow into sun, except for the briefest possible period and then only if
unavoidable
DON’T climb or descend in long straight lines without clearing the aircraft’s
blind spots
DON’T skimp cockpit checks
DON’T do aerobatic departures after release
DON’T let the speed build up too rapidly in the initial descent phase
DON’T do steep turns on tow
DON’T park a few metres in front of the glider with your engine running while
waiting for the next tow - it covers everyone with dust and takes forever to
take up slack
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10.
EXPANDED GUIDELINES FOR OUTLANDING
RETRIEVE APPROVAL
10.1
GENERAL
Although it sounds simple enough, the task of retrieving a glider from a
paddock should not be underestimated. Such operations are fertile ground
for accidents and there are several clubs in Australia which do not permit
them for this reason.
The difference between an outlanding retrieve and a normal landing back at
base is that a farmer’s paddock is just that, a paddock, with no consideration
given to ever landing an aircraft of any description in it. There may be some
exceptions to this, where a glider pilot has managed to find, wittingly or
unwittingly, a paddock which is used by a farmer in the operation of his own
aircraft, but this will be the exception rather than the rule.
10.2
PRELIMINARIES
Firstly, you should not set out on an outlanding retrieve unless you have
been assured by the glider pilot, by telephone or radio, that you have the
owner’s permission to land on the property (GFA Operational Regulation
10.4).
Secondly, do not carry out an outlanding retrieve if a total fire-ban is in force.
State law, such as Regulation 39 (1) pursuant to Section 46 of the Country
Fires Act 1989, prohibits it. Most tugs have downward-facing exhausts and
these can set fire to a paddock very easily. Even sideways-facing exhausts
are not immune to the problem. The worst thing is that the problem will not
show up on the landing, as there is little coming out of the exhaust. It will
happen on the subsequent take-off, at full power, and all you do is fly away
from the problem!
Don’t risk it. You will not be forgiven for starting a bushfire or grass fire and
it is quite on the cards that you will be prosecuted. The prosecution will be
well-deserved.
Thirdly, make yourself familiar with the glider-pilot’s “five S” rule and run
through it in your mind prior to departure.
Finally, you must be sure that you have (a) enough fuel and (b) enough
daylight to complete the retrieve safely and legally. Don’t leave home if you
can’t read a daylight/darkness graph or compute your fuel consumption for
an aerotow retrieve. Be sure you know how to do these things properly.
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10.3
THE LANDING
If all the preliminaries have been satisfied, we now have to consider what
you will be faced with in comparison with anything you have done before.
The fact that the paddock is not a dedicated airfield results in the following
factors needing consideration when planning an outlanding retrieve:-
10.3.1 Lack of markings
There will be no markings. No gable markers at the sides, no threshold
markers, nothing to indicate where the actual landable strip is. In fact there
is nothing to tell you whether the strip is landable or not. A glider pilot is
formally trained how to cope with this kind of assessment. So must a tugpilot before attempting an outlanding retrieve.
10.3.2 Obstacles on the approaches
The approaches will probably not be clear; there is no reason why they
should be. You will have to be exceptionally careful in setting up your circuit
and approach into the paddock. If it is a long time since you did any
precautionary searches with an instructor, book out an aero-club aircraft and
do a few. They will stand you in good stead.
10.3.3 Lack of wind information
There will be no wind-sock and you will have to rely on raw information like
water on dams, dust rising from cars on dirt roads, assessing drift from the
cockpit, etc. Another good reason to brush up on your precautionary
searches if you are a bit rusty.
10.3.4 Unreliable information and pressure to perform
Glider pilots have little interest in a trailer retrieve if an aerotow is available.
Retrieve crews feel much the same way. When you speak to the glider pilot
on the phone or radio prior to setting out on the retrieve, you may find quite a
lot of pressure applied to get you to come and pick up the glider. For this
reason you should regard telephone or radio information about paddock
quality as, at best optimistic and at worst downright misleading. Make sure
the glider pilot understands that, should you agree to go and pick up the
glider, it is your absolute right to refuse to land if you don’t like what you see
from the air when you arrive overhead. Do not feel pressured into
attempting a task if you are not satisfied it is safe.
10.3.5 Apply the glider pilots’ five ‘S’ rule
Size. Should be adequate for the landing and subsequent take-off with the
glider on the back. Use corner-to corner if necessary. You MUST know the
take-off performance of your tug with a glider on the back, not just a sketchy
“she’ll be right” approach, but an intimate knowledge of its performance in
various conditions with various gliders on the back.
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Slope. If a slope is detectable from overhead or close to overhead, it is
almost certainly too much to attempt a landing. If, by standing off to one
side, you assess that there is a slope but it is manageable, plan on landing
up the slope and taking off down the slope. To make this feasible, the wind
either has to be very light or, if it is a bit stronger than very light, is biased in
favour of the downhill take-off. You will then need to decide whether it is
best to land down the hill but into wind, or land uphill and accept a downwind
component. Uphill take-offs with a glider on the back are a no-no, unless
there is a howling gale blowing along the strip in your favour.
Surface. A surface which is suitable for a safe landing may not be suitable
for a subsequent take-off, especially if it is soft. Rabbit and wombat holes
are also a hazard. Remember that you still have the right to refuse to tow
the glider after you have landed, if you decide that the surface is so soft that
it will compromise the acceleration of the combination on the take-off run.
Many a nasty outlanding retrieve accident would have been avoided if the
tug pilot had exercised this right.
Stock. Stock animals are usually obvious, but sheep may be sheltering
from a hot sun under a clump of trees. They can be a nuisance if they run
out in front of you at the last moment. Cows are curious animals and are
often attracted to the cellulose in the finish of fabric covered aircraft, which
they will proceed to lick with their enormous tongues. They may even get
really enthusiastic and start to munch your control surfaces. Nothing like a
nice rudder for lunch, especially if you’re a bit short of fodder! Many of the
older fabric-covered gliders have been damaged this way, but when cows
are in this mood, they don’t seem to mind whether the aircraft has an engine
or not. Not many pilots are game to try to shift a cow if it is making a meal of
their aircraft. If a cow chases you, its probably a bull.
Ostrich farms are definitely off limits. Even if you get permission to land on
or near one of these farms, which is unlikely, the birds will go out of their
minds if you fly near their paddock. At $10,000 per bird, they are expensive
creatures to frighten. Under no circumstances should you agree to go on a
retrieve “on spec”, without owner’s permission, from or close to an ostrich
farm. Be warned.
Surrounds. You will need good approaches to land, but more to the point
you will need very good obstacle clearance for your projected take-off path.
Trees, telegraph poles and main grid power lines are very obvious and you
will be able to make a decision on these items without difficulty.
Single-wire earth return (SWER) lines are a different matter and they have a
history of tripping up aircraft and gliders in many parts of Australia. Some
parts of the country do not have SWER lines, as the ground is not
conductive enough to provide an earth return, but in those parts of the
country where they can be used, they are an attractive solution to the
provision of electrical power to individual homesteads at low cost. There are
thousands of them in rural areas.
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They are a real pest to aircraft. The poles are skinny and, for environmental
reasons are often concealed among trees. A single wire means that there
are no cross-arms, adding to the difficulty of finding the poles. In the middle
of the afternoon they cast no shadow, further compounding the problem,
although you may be luckier in the evening. The poles are often a long way
apart, a kilometre being quite common, and the wire itself is impossible to
see until it is too late, especially if it has been sand-blasted to eliminate the
glint for environmental reasons.
SWER lines do not necessarily follow fence lines. They may cut the corners
off paddocks, stretch across at some intermediate distance into the paddock
or wander off completely at random. The best guidance is that, if you can
see a homestead, there will definitely be a SWER line leading to it. You
MUST find it before you attempt a landing.
It would be nice if that were the end of it. Unfortunately there are often
junctions leading to other parts of the property and you may get a nasty
surprise by blundering into one of these just when you thought you had
located them all.
That’s the bad news. With SWER lines, the only good news is that they are
not very high off the ground and if a glider strikes one it will be at a late stage
of the approach to land (unlike, for example, a crop-spraying aircraft) and
therefore at a quite low 50-55 knots, with not far to fall to the ground. This
often results in a relatively low-energy accident which has historically proved
survivable in a number of cases, although almost always with serious injury.
Take no comfort from the low-energy argument, however. Tugs carry highoctane fuel, which is an obvious hazard in a high-voltage environment.
10.3.6 Further reading
For anyone training for outlanding retrieve approval, especially information
relating to the location of powerlines prior to landing and the effect of local
winds, the following book is recommended reading:
Flight at Lower Levels, by John Freeman
Available from Wakefield Press, Box 2266, Kent Town, SA 5071
Tel (08) 8362 8800, Fax (08) 8362 7592
10.3.7 Removing the rope
It is prudent to remove the rope before setting out on an outlanding retrieve.
Don’t forget to put it in the tug! If you are setting out on a retrieve
immediately after an aerotow at home base and you therefore have the rope
still attached, prepare to drop it at the other end on one of your inspection
passes before landing. Under no circumstances should a rope-dropping
pass be used as an excuse to do a beat-up - there is more at stake, in terms
of gliding’s reputation, than the momentary gratification to the pilot of such
antics, to say nothing of the risk to any bystanders who might have gone
undetected by the pilot.
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Some clubs use a rather shorter rope than normal, to effectively increase
available take-off distance. Other clubs believe that, if you need to take a
few metres into account by using a slightly shorter rope, take the trailer, you
have no business aerotowing from that paddock. Both arguments are valid
and both have their adherents. You will be expected to adhere to your club’s
rules on this, as well as other, matters.
Whatever size of rope you have, landing with it attached to the tug makes no
sense when you are going into an unknown paddock. There is too much
chance of snagging it on something (or someone) you hadn’t noticed. Either
carry it in the aircraft or drop it before landing.
10.4
THE TAKE-OFF
There is a basic rule to maximise your chances of survival in a aerotow takeoff from a paddock - PACE OUT THE AVAILABLE DISTANCE.
10.4.1 Pacing out the paddock
Pacing out the paddock has a number of advantages, viz.:1.
It obviously tells you how long the paddock is.
2.
You can check for surface irregularities, soft patches, wombat holes,
etc.
3.
You can double and triple check for any powerlines you may not have
spotted from the air.
4.
You may find a few nasty surprises, such as old fences hidden by long
grass.
5.
You can check out obstacles to the side of the take-off path, which may
cause turbulence on a crosswind take-off. Look in particular for
obstacles which might cause a downdraught and be particularly
suspicious about a paddock in the lee of a hill.
10.4.2 Factors affecting the take-off
10.4.2.1 Side-slope
This may not bother you very much, but it can cause real problems for a long
wingspan glider. You may have to alter the take-off run to take slide-slope
into account. If this is the case, you may have to make major alterations to
the overall plan.
10.4.2.2 Lack of wingtip holder
In the middle of nowhere, it is often impossible to find a wingtip holder. This
necessitates a wing-down take-off, which is quite feasible, but only if the
surface is suitable. See 10.4.2.3.
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Practice wing-down take-offs at your home site as part of your training for
outlanding retrieve approval. Cross-country glider pilots need this practice
just as much as you do.
10.4.2.3 Long grass,etc
There are two considerations with long grass. Firstly there is the effect on
take-off acceleration of an overall carpet of long grass. This cannot always
be taken into account by the tug’s “P” chart and on the basis of the
information provided on the chart, aided by your own Mk 1 eyeball, you will
have to decide whether to proceed with the take-off or not.
Secondly there is the effect of patchy areas of long grass or other vegetation
such as onion weed or thistles, which do not appear to be thick enough to be
a problem for the tug.
Generally speaking they aren’t, but they certainly will be for the glider. Any
vegetation over about 10 cms long rules out a wing-down take-off, as the
glider pilot will not be able to keep straight due to the drag of the wing in the
grass. Don’t try it.
Even with a wing-tip holder, you may still be in trouble. Modern gliders often
drop wings some considerable time after the wingtip holder has let go, a
function of their rather high angle of attack with the tail on the ground,
combined with the spiral propwash from the tug. If the wing drops into long
grass, a groundloop is a certainty. We prove it about half-a-dozen times
every year.
Don’t take chances with long grass and don’t drop your guard just because it
looks like it’s only in small patches. If in doubt, get the trailer.
A final word about wingtip holders. You may find an enthusiastic volunteer
from the farmer’s family, who would love to run the wingtip for you. Fine, but
be sure this person is very carefully briefed, as almost everyone holds back
on the wing the first time they do it. This is a problem both the tug-pilot and
the glider pilot can do without at any time, but especially in a paddock takeoff.
10.4.2.4 Soft ground
This will not necessarily cause the glider to ground-loop, but it may have a
dramatic effect on the acceleration of the combination, to the extent that the
take-off may have to be aborted. In some cases the combination may stop
accelerating at somewhat less than take-off speed.
10.4.3 Take-off technique
You will need to know the effect of flaps on the take-off performance of the
tug. Even if the normal technique back at home base is to do flapless takeoffs, flaps may be useful in a paddock take-off to get the aircraft up out of the
weeds and into ground effect as soon as possible. This can work very well if
the ground is soft or the grass is long, but consult the aircraft’s flight manual
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for details on the use of flaps. Flight manual information may differ from
what your instinct might suggest, for example the use of full flap instead of
half-flap for a short-field take-off in some types. If used, the flaps can then
be gradually retracted as soon as possible after the combination is airborne
and the climb-out is then quite normal. If you are towing a flapped glider, the
glider pilot will set his/her flaps to get the glider airborne as soon as
practicable.
When taking off in a paddock, there is no need to open the throttle any more
rapidly than normal, as long as it is not too prolonged. If the available takeoff distance is so marginal that the rate of throttle-opening is going to make a
serious difference, you would be well advised to abort the attempt before you
get too far and advise the glider pilot to organise a trailer retrieve.
11.
THE MANAGEMENT OF ENGINES AND RELATED
ITEMS IN THE GLIDER-TOWING ROLE
11.1
AIR-COOLED HORIZONTALLY-OPPOSED ENGINES
(LYCOMING, CONTINENTAL, ETC)
11.1.1. General
The horizontally-opposed or “flat” engine is the most common type used in
light aircraft. In glider tugs, engines of this design are usually of four or six
cylinders. Because of its layout, two of the engine’s cylinders are directly
influenced by cooling airflow, the remainder being to some extent shielded.
There is no forced-fan cooling of “flat” engines, except when installed in
helicopters.
Although these engines are referred to as being air-cooled, they actually
depend on a combination of cooling air from outside and a flow of oil on the
inside which conducts heat away from critical parts of the engine before itself
being passed through an oil cooler.
These engines depend on a pressure slightly higher than atmospheric
pressure being developed under the engine cowling during flight. Under the
cowling there are baffles placed in strategic positions around the engine, to
direct the air to the places where it can do the most good.
11.1.2 Daily inspections
As adequate cooling of the engine depends on the air reaching out-of-theway places, such as the back of the rear cylinders of the engine and the
middle cylinders of the flat-six, the condition of the baffles is critical. If they
are in poor condition, they can allow leakage to occur and some parts of the
engine may not receive cooling air.
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Pilots should check on the DI that the baffles are themselves in good
condition, that they mate correctly with the engine cowlings and that the
sealing strips attached to them are in good condition. Any or all of these
factors can considerably affect engine life.
Of all the things that affect the correct operation of an air-cooled engine, the
condition of the under-cowling baffles is probably the most critical.
Experience seems to indicate that, in a hot country like Australia, it is best
not to fill the oil right up to the “full” mark on horizontally-opposed engines if it
is intended to carry out local towing operations only. About two-thirds to
three-quarters full will suffice, any more and the engine is likely to either run
hot or throw some of the oil out. Only top it up if cross-country towing is
intended. Make sure the correct grade of oil is used; this will depend on
whether the engine is well into its life or is still being run-in after
reconditioning. Check with your club’s tugmaster if in doubt.
A typical airflow path through the cowling of a horizontally-opposed engine.
The importance of the baffle at the top rear of the engine will be apparent.
There may be additional baffles between the cylinders. The condition of
these baffles is critical to proper engine cooling in the glider-towing role. A
cowl flap is also shown in this installation.
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11.1.3 Pilot operation
11.1.3.1 Taxying and run-up
Because the engines are pressure-cooled, such pressure being derived from
the aircraft's movement through the air, they receive negligible assistance in
directing the airflow around the engine when they are on the ground.
Excessive ground-running causes local overheating, which spells trouble
later on in the engine's life. Waiting for the oil temperature to come up into
the green before taking off will probably contribute to this kind of problem.
The manufacturers of these engines state in their manuals that the engines
are ready to fly when they will accept full power without hesitation. This is a
subjective judgement, because full power should never be applied abruptly
and a slow application may not prove conclusively that the engine is ready.
As a guide, unless the weather is abnormally cold, the engine should be
ready to fly after a ground-running period (including magneto and propeller
checks) of not more than about 4 minutes. The oil temperature will stabilise
during the first flight.
Some horizontally-opposed engines (e.g. the Lycoming 0-540) have a
counterbalance weight on the crankshaft. Very rapid opening of the throttle
will result in excessive forces being applied to this weight, which could cause
damage. Engines which have this limitation are usually placarded "Idle to
full throttle, 2 seconds minimum".
Whether placarded or not, gentle throttle-handling is a good
recommendation. 2 seconds should always be regarded as an absolute
minimum and it could with advantage be twice that figure. No gliding club
will thank you for damaging its engine by ham-fisted handling.
11.1.3.2 Climbing
Full throttle should always be used for glider towing, unless there is an
overriding operational reason for a reduced power operation.
Reasons for operating at reduced power may be:1.
The engine has a limitation on the amount of time spent at full power
(this applies to some engines fitted with constant-speed propellers).
2.
A low-speed glider is being towed, where a speed reduction at full
power may result in an excessively nose-high attitude and a dangerous
reduction in forward visibility.
The reason why full power should be used where possible during towing is
that the carburettors fitted to most glider tug engines have a power jet fitted
to them. This provides an excess of fuel at full throttle, which is used to cool
the engine evaporatively. Reducing power by a small amount is therefore
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likely to contribute to overheating, which sounds contradictory but is in fact
true.
Even with everything done properly, climbing at relatively low airspeed and
high power settings generates high under-cowling temperatures. The
cooling effect of the air varies roughly as the square of the airspeed, so small
changes in speed can cause relatively large changes in cooling effect. After
a full-throttle climb of, say, five minutes, it is quite possible that the engine’s
exhaust valves are approaching red heat. The engine designer does all he
can to alleviate the problem of localised heating, by careful design in the
valve-gear area, and airframe designers do their bit by careful cowling
design. Even so, the area around the cylinder heads and particularly close
to the valve-seats and guides gets extremely hot and is very prone to
cracking. In cases of repetitive overheating, valve stems can actually break
and the valve heads drop into the cylinders.
Cylinder-head cracking is the biggest cause of trouble and expense with aircooled engines. There seems to be an increasing world-wide opinion that
the biggest source of this trouble is the climb, more than any other phase of
the flight.
As excessive heat is the enemy of an air-cooled engine, and full throttle is
highly desirable to provide an excess of fuel for cooling purposes, it almost
goes without saying that the mixture should never be leaned during a fullpower climb, unless the engine is running roughly for reasons of density
altitude. Even then it should be done with care and by the minimum amount
necessary to restore smooth running.
11.1.3.3 Descending
Shock-cooling is the biggest problem on the descent and the number one
enemy is speed. We know that the engine is going to be pretty hot by the
time it gets to the top of the climb. If the speed is allowed to increase very
rapidly after release, the heat-soaked engine will be hit with a very rapid rate
of cooling, remembering that the rate of cooling varies as the square of the
airspeed. Increasing speed very rapidly from, say 65 knots on the climb to,
say 100 knots for the descent, causes very rapid cooling, greatly exceeding
any cooling of the cylinders which might occur from rapid closing of the
throttle.
This is not condoning rough handling of the throttle, nor is it suggesting that
clubs should necessarily descend at idle RPM.
However, overseas
experience indicates that operators using idle RPM for the descent have no
greater rate of cylinder cracking than clubs which use our “traditional”
descent method of about 2200 RPM and 100 knots (Pawnee 235).
Smooth throttle handling and a slow build up of speed are the answer. You
can close the throttle quite a long way and you won’t do much harm,
provided the throttle is not closed really rapidly and, most importantly, you
accelerate at a very moderate rate to the chosen descent speed. Flying
schools which teach plenty of practice engine failures do not crack cylinders
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at an abnormal rate, probably because the pilot is instructed to reduce speed
gradually to the max L/D speed and then maintain that relatively low speed
until their “go-around” point. “Cowboy” departures, which increase speed
very rapidly in the first few seconds, will prove lethal to a club’s bank
balance. You will probably get sacked if you do it.
At the other extreme, we are all familiar with the tug pilot who uses up huge
volumes of sky trying to get the tug to come down. There is no need for this
- start closing the throttle smoothly, lower the nose and start increasing
speed, but do everything MODERATELY. You will get the descent started,
instead of going on a tour of the local countryside, and you won’t be harming
the engine.
Monitor the cylinder head temperature (CHT) gauge. If you haven’t got one,
get one fitted. Know the maximum permissible CHT for the tug you are
flying and aim to descend in such a way as to lose 50ºF or less per minute
(most American aircraft are in ºF). This can be achieved without difficulty by
building up the speed gradually, not diving steeply and increasing speed to
100 knots or more in a few seconds. When the CHT has decreased to
300ºF, the danger period is over and shock-cooling is most unlikely to occur
below that figure, whatever you do with the throttle.
Some tug aircraft are fitted with a “shock-cooling gauge”, consisting of a
sensor on the engine and a little yellow light on the instrument panel. If the
rate of cooling is too high, the light comes on. The pilot then increases
power slightly or (better) slows down a bit, or maybe a combination of both,
until the light goes out.
11.2
AIR-COOLED IN-LINE ENGINES (GYPSY MAJORS, ETC.)
11.2.1 General
As their name suggests, these engines have their cylinders arranged in-line,
one behind the other. This places only one cylinder under the direct
influence of cooling air, the rest being somewhat in the shadow of this
cylinder. These engines may be of four or six cylinders, although only the
four cylinder type is known to be in glider-towing service in Australia.
Although the actual engine design is conventional, like an ordinary fourcylinder car engine, the in-line aircraft engine is inverted, with the crankshaft
at the top of the engine and the valves at the bottom. This makes it easy to
mount the propeller directly onto the crankshaft and still have adequate
ground clearance without having to design a very stalky undercarriage.
However, it also means that a conventional sump cannot be used to hold the
oil and these engines all have a separate oil tank. It is important that the
level in this tank is checked regularly, as these engines tend to have rather
heavier oil consumption than the horizontally-opposed type.
Like the horizontally-opposed engine, reliance is placed upon both air and oil
to assist in keeping the engine cool, with oil playing perhaps a slightly more
important role in the in-line design. In terms of pilot operations, the in-line
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engine is handled in exactly the same way as the horizontally-opposed
engine, only the numbers (RPM, IAS) are different. There is therefore no
need for a separate section on handling for this type of engine.
11.2.2 The “Armstrong” starter
Many aircraft fitted with in-line engines are of vintage type, e.g. Auster, Tiger
Moth. Most of these types have no electrical system, so of course they do
not have a starter motor. They must be started by swinging the propeller by
hand - the so-called “Armstrong” starter.
Many people have a horror of even touching a propeller, let alone swinging it
with the ignition switched on. While such a fear is understandable, and is
even promoted during flying training these days, there are some aircraft
which would never fly if we did not learn how to do it properly and safely.
Quite a number of these aircraft have gravitated to the gliding movement, so
there will be a continuing need for people to know how to start them
properly. Hence this section.
11.2.2.1 Gypsy Major engines
Most of the engines which need prop-swinging are variants of the
de Havilland Gypsy Major design, so this section will concentrate on this
type of engine. Gypsy Majors are “left-hand tractors”, which means that they
turn in an anti-clockwise direction when viewed by the pilot. Because of the
lack of a starter motor, they will be specially set up so that the prop is in a
convenient position to swing it when it comes up against a compression.
Provided everything is done properly, there is no particular hazard in starting
this type of engine by hand.
The answer lies in unvarying and uncompromising adherence to known safe
practices. A formal start procedure is agreed upon and rigidly adhered to. A
suggested start procedure, which is known to work well, is as follows:
Pilot in cockpit, assistant forward and to the pilot’s side of the propeller.
It is assumed that the engine has been primed under the cowling
before the pilot climbs aboard. The assistant MUST hear the pilot say
clearly the following:“Brakes on (if applicable), fuel on, throttle closed, switches off”.
If brakes are not fitted (e.g. some Tiger Moths), ensure aircraft is
properly chocked.

Pilot then requests “Suck in”. Assistant pulls propeller through four
blades in the normal engine direction, then ensures that the blade at
two o’clock (as viewed from the front) is up against a compression.

Maintaining position in front of and to one side of the propeller and with
one hand on the trailing edge of the blade in the two o’clock position,
assistant calls “contact”, or “switches on” if preferred.
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
Pilot clearly repeats the words and switches on both magnetos. The
ignition system is now live.

Assistant smoothly pulls propeller blade over the compression,
following the movement through so as to take his entire body away
from the arc of the propeller. The engine should start without further
ado.
If it fails to start, it is appropriate to try again a few more times before maybe
making some adjustments to the fuel settings. Each time, the ignition must
be switched off between attempts and the assistant must not touch the
propeller until he says “Switches off”. This MUST be acknowledged by the
pilot. Only when the assistant is ready and has the propeller up against the
compression will he say “contact” and have another go.
ESSENTIAL POINTS FOR HAND STARTING.
A PILOT MUST NEVER SWITCH ON THE MAGNETOS DURING HANDSTARTING UNTIL REQUESTED TO DO SO BY THE ASSISTANT.
IT IS NOT NECESSARY TO USE FORCE IN SWINGING THE
PROPELLER. PULL IT OVER THE COMPRESSION IN AS RELAXED A
WAY AS POSSIBLE. IT IS NOT MUSCLE POWER THAT GETS THE
ENGINE STARTED, BUT THE ENERGY PROVIDED BY THE CORRECT
FUEL/AIR MIXTURE AND THE RETARDED SPARK FROM THE IMPULSE
MAGNETO. YOU ARE JUST A HUMAN STARTER MOTOR. ANY
ATTEMPT TO USE FORCE MAY PUT YOU OFF BALANCE AS YOU
SWING THE PROP.
It is not entirely unknown for the engine to refuse to start at the first few
attempts. This may be for one of a number of reasons.
The first is a jammed impulse on a magneto. This will be discernible by the
lack of a loud clicking noise when the propeller is pulled over a compression
with the ignition off. The impulse device is essential to retard the spark for
starting and it is unlikely that the engine will start until it is freed. The most
common ritual for doing this is inserting a lump of wood through one of the
apertures in the cowling and giving the offending magneto a good thump.
This almost always does the trick.
If the impulse is clearly working and the engine still won’t start, you have a
fuel problem. If the pilot has primed the engine with the tickler before
boarding the aircraft and if you have pulled through the statutory number of
blades before having several abortive starting attempts, the likelihood is that
the engine is flooded. Tackle this as follows:
Assistant to pilot - “Brakes on (or chocked), switches off, throttle wide,
blow out”. Pilot acknowledges each stage.
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
Assistant pulls engine BACKWARDS eight blades, then says to pilot
“throttle closed”. Pilot closes throttle and acknowledges.

With throttle closed and switches still off, assistant sucks in four blades.
Normal starting procedure then applies.
11.2.2.2 All other engines
For tug aircraft fitted with engines other than Gypsy Majors, it is likely that
they will be electrically started. This makes them difficult and possibly
hazardous to hand-start, for four reasons.
1.
The propeller is unlikely to be positioned on the crankshaft with handswinging in mind.
2.
American horizontally-opposed engines are “right-hand tractors”, the
opposite of Gypsy Majors. This makes them awkward to hand-swing
safely unless you are left-handed by nature. For some multi-seaters,
such as Cessna 180 or Maule Rocket, it also places the assistant on
the opposite side of the fuselage to the traditional left-hand command
seat, making communication more critical.
3.
If you are hand-swinging because the battery has gone flat, it is likely
that the starter is still engaged, because in most cases it will not throw
out until about 300 RPM after start-up. The extra drag of the starter
motor will make it difficult or impossible to hand-swing the engine and
you may get hurt in the attempt.
4.
Many aircraft with these engines (e.g. Pawnee) are rather high off the
ground and, unless you are a tall person, you may have to stretch up to
a dangerous degree to reach the blade you want.
All in all, when faced with an electrically-started engine in an aircraft with a
flat battery, it is recommended that it be jump-started from an external
battery in preference to hand-starting it.
11.3
LIQUID-COOLED ENGINES
In an attempt to reduce the very high overhaul costs of conventional aero
engines, various automotive engines have been tried in aircraft over the
years.
Two different engines have been tried in glider tugs in Australia in recent
times. Both aircraft are Pawnees, one being a PA-25-235 with its Lycoming
0-540 engine replaced by a 454 cu.in. NASCAR-modified Chevrolet V8, the
other being a PA-25-150 with its Lycoming 0-320 replaced by a 3.8 litre Ford
V6.
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The Chevrolet-engined Pawnee was used mainly for top-dressing and only a
small amount of glider-towing was done. It has now been restored to its
original Lycoming power-plant.
The Ford-engined Pawnee, known as “Autotug”, is a developmental aircraft
and has amassed a reasonable amount of general flying and glider-towing.
It is busy towing gliders and is still being developed.
Without going into too much detail, as development is not yet complete, the
major differences between operating an automotive engine and an aero
engine in the glider-towing role are as follows :1.
The engine develops its maximum power at much higher RPM than an
aero-engine, typically about twice as fast. A conventional light-aircraft
propeller does not take kindly to this level of RPM, as the tips exceed
supersonic speed and the propeller produces more noise than thrust.
This necessitates some form of reduction drive to slow the propeller
down to suitable RPM. In the case of Autotug, as with most modern
auto-engine installations in aircraft, this is achieved via a toothed belt.
This is an additional, and rather unfamiliar, item for pilots to get used to
checking.
Autotug shows engine RPM on its tacho, but some operators may
prefer to show propeller RPM, similar to the now-defunct Continental
“Tiara” engine. From the pilot’s point of view it probably doesn’t matter
very much, but the engine tacho is easier to install.
2.
The liquid cooling system is a new feature for almost all pilots to get
used to. Coolant temperature, pressure and level are monitored in
Autotug, as well as usual aero-engine features such as oil temperature
and pressure. The end objective is to produce a cooling system which
does its job effectively and demands no special treatment. Although
not yet found to be necessary in Autotug, in some installations a
ground-running electric fan may be necessary in very hot weather.
3.
There is no mixture control. A choke is fitted for cold starting, but there
is no provision for weakening the mixture to compensate for a changing
fuel/air ratio as the aircraft climbs. In tests up to 10,000 feet AMSL, this
has not proved to be a problem with autotug. (Note: Autotug has a
dual-carburettor system, but a modern electronic fuel-injection system
will probably be fitted for production).
4.
No carburettor hot-air system is fitted. This again has not proved to be
a problem in a number of flights in carby-icing conditions, but in any
case the injection system intended for production will probably
eliminate all such problems anyway.
5.
Because of the liquid-cooling system, thermal shock is not a problem.
After release, the throttle can be closed a rapidly as a pilot wishes,
without risk of shock-cooling the engine.
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However, a note of caution is appropriate here. A Pawnee descending
with its throttle closed can achieve a very high rate of descent,
something in excess of 2,000 feet per minute. Descending at this rate
into a busy circuit area is a highly dangerous practice, for obvious
reasons. Regardless of their improved tolerance to rough handling of
the throttle, tug aircraft with liquid-cooled engines should be descended
in exactly the same way as those with air-cooled engines. This enables
the pilot to check his blind spots and also makes the tug predictable in
its behaviour.
6.
Autotug has no back-up ignition system. It is likely that production
automotive-engined tugs will have this feature, with its own standby
battery, to provide a system redundancy similar to that of a
conventional dual-ignition aero-engine.
Whichever aircraft/engine mix is chosen, there will almost certainly be a
number of auto-engine conversions carried out in the future, as the fuel
consumption of these engines is about half that of a Lycoming 0-540 and the
overhaul costs are way down, about an eighth of aero-engine costs. Pilots
will need to get used to the modes of operation of the various conversions
and modifications to normal operating practices may have to be made if the
introduction of these machines is to be smooth and trouble-free.
11.3.1 Partially liquid-cooled engines
Aircraft engines are now available in which the block and cylinder barrels are
air-cooled, but the cylinder heads are liquid-cooled. The intention is to
improve the cooling and stabilise the temperature around the region of the
engine most susceptible to extremely high temperatures, i.e. the area around
the valves. The concept seems to work very well.
The two best-known examples of this type of engine flying in Australia are
the Rotax 912 and 914, respectively normally-aspirated and turbocharged
versions of a geared flat-4 design. The engines turn at 5,800 RPM at full
throttle, producing 2,470 RPM at the propeller after passing through the
2.27:1 reduction gearbox. Both engines are fully certificated and reliability
appears to be good to date.
Although these two engines are not powerful enough for present-day tugs
(79 hp for the 912, 115 hp for the 914), they may prove to be attractive for
lightweight tugs which will no doubt be required when the lightweight gliders
now at the prototype stage reach production and gain acceptance. The
engines are already used in many powered sailplanes and ultralights.
It is highly likely that these two designs from Rotax will be joined by others
when the benefits of liquid cooling the critical parts of an engine are realised
by other manufacturers.
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11.4
PROPELLERS
11.4.1 Fixed pitch propellers
This is the most common type of propeller fitted to glider tugs. It has the
advantage of simplicity, relatively low cost and ease of operation. The
disadvantage is that it has to be carefully pre-selected for its intended job.
For example, an aircraft intended primarily for long-distance cruising would
have a fairly coarse propeller fitted. This means it would be quite efficient at
its cruising speed, but would not produce anything like maximum RPM at low
speed. An aircraft fitted with such a propeller would have very sluggish takeoff and climb performance, the price paid for good performance in the cruise.
Conversely, a fine-pitch propeller would enable plenty of RPM to be
developed at low speeds during the take-off and climb, but would over-rev
the engine when the speed built up in level flight.
For glider-towing, a fine pitch propeller is preferable, as we are interested
primarily in climb performance. For our purposes, a propeller which
produces something within about 10% of maximum RPM at about 65 knots
at full throttle on the climb is close to ideal.
Unfortunately, such a propeller is likely to cause overspeeding of the engine
on the descent. It is illegal to fit a propeller which will allow the engine to
exceed maximum RPM at the aircraft’s Vne. For this reason we often have
to accept a compromise propeller which produces less thrust than we would
really like on the climb, but have no choice but to accept it.
Thus a Pawnee 235, theoretically a 235 hp aircraft, will only achieve about
190 hp at 65 knots in most cases, because we cannot fit a propeller which
will permit full RPM on the climb because of the risk of over-revving on the
descent.
It is therefore apparent that a fixed-pitch propeller is, at best, a compromise.
It is a compromise we must be prepared to accept if we want the lightest and
simplest installation available.
11.4.2 Variable-pitch and two-speed propellers
There are no variable-pitch (non-constant-speed) propellers in glider-towing
service in Australia. There are a few two-speed propellers around; all fitted
to 0-540 Lycoming engines in some IMCO Callair aircraft. This type of
propeller allows fine pitch to be used for the climb and a coarser setting for
the descent. Although such a propeller does not have a great deal of
flexibility for a cruising aircraft, it is quite useful for glider-towing.
11.4.3 Constant speed propellers
This is a variable-pitch propeller which will maintain any given RPM set by
the pilot, regardless of throttle setting or aircraft speed, by varying the pitch
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of the blades according to the load it senses on them. Blade movement is
usually accomplished hydraulically, using engine oil, although electric
constant-speed propellers are available and may be used on some
installations.
A constant-speed propeller does have defined limits, beyond which it
behaves like a fixed-pitch propeller. Thus it has a fine-pitch stop and a
coarse-pitch stop, both set by the manufacturers.
However, within its
operating range, it changes its own pitch to maintain a constant RPM without
the need to touch the engine controls. This enables the maximum
performance to be obtained from the engine in most normal phases of flight.
For glider-towing, fully-fine pitch will be used for the climb, allowing
maximum RPM (and thus maximum power) to be produced. On the
descent, propeller pitch can be coarsened to avoid over-revving and to
enable the pilot to feed some throttle into the engine as a buffer against
shock-cooling. However, if this latter technique is used, a “propeller” check
needs to be done on final approach to ensure the prop is in fully-fine pitch
before landing, to cater for the possibility of a baulked approach and goaround.
If a constant-speed propeller is fitted to the aircraft to be used for tug pilot
training, or to the type to be flown by the candidate after training, it will be
necessary to obtain an endorsement on this kind of propeller before starting
training. Most CAR 149 glider towing delegates are not authorised to give
such endorsements, unless they also happen to be CASA-qualified flight
instructors.
11.4.4 Cowl flaps
These may be fitted to some types as an aid to controlling under-cowling
temperatures and prolonging engine life. They may be fitted externally (e.g.
Cessna 180, IMCO Callair) or internally (e.g. modified Pawnee). As a
general rule, they are fully opened for the climb and fully closed for the
descent.
They are somewhat easy to forget in the busy task of glider-towing, and this
error may be either one of forgetting to open them for the climb, or to close
them for the descent. Of the two, forgetting to open for the climb is the most
likely to cause harm to the engine, as some local overheating may occur at
critical points.
Some designs, the Callair being a good example, have the cowl flap control
placed so that the pilot’s knuckles contact the control if it is in the closed
position and the throttle is opened fully. Grazed knuckles act as a very
effective reminder to open the cowl flaps and it is a pity more designers did
not give this amount of thought to the ergonomics of their cockpits.
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11.5
FUEL REQUIREMENTS, AVGAS AND MOGAS
Most of the aero-engines fitted to glider tugs are very basic versions of a
particular engine type. They are usually of fairly low compression and are
fitted with carburettors rather than fuel injection. There are no turbo-charged
or geared aero-engines known to be in glider-towing use in Australia at
present, although the Cessna 175 with a geared Continental GO-300 has
been used successfully in the past.
Some of these low-compression aero-engines have been certificated by
CASA for the use of motor-car gasoline (Mogas) instead of aviation gasoline
(Avgas). Only those engines which have the Supplemental Type Certificate
(STC) in their flight manual are legally able to use Mogas.
11.6
ROPES, RINGS AND WEAK-LINKS.
Ropes
Ropes are usually of polypropylene or polyethylene, both of these materials
being adequately strong and with enough elasticity to give a good ride for the
glider pilot without excessive stretch of the rope. Nylon is not satisfactory, as
it is too stretchy. Natural fibre (sisal) rope works OK, but lacks durability, in
particular abrasion resistance. Wire rope should not be used.
The most common diameter for aerotow ropes is 10mm, which gives a very
strong rope with good resistance to abrasion. 8mm rope is strong enough
for aerotowing use when new, but wears rather rapidly and thus loses
strength.
Splices are ideal for joining pieces of rope together or for making the looped
ends into which the rings are inserted. Splices retain most of the rope’s
original strength, but it must be admitted that splicing is something of a dying
art and a relatively small number of people know how to do it properly.
Bowline knots are often substituted for splices at the ends of ropes. These
have the advantage that they allow easy replacement of rings and the knots
can be easily re-tied if worn by abrasion. Abrasion can be considerably
reduced by protecting the bowline with half a squash-ball pushed over the
knot. Bowlines retain about 85% of the rope’s original strength.
The minimum length for an aerotow rope for general use is 55 metres. To
remind you why it is in your interests to adhere as strictly as possible to this
length, refer back to the section on tug upsets. For a number of reasons,
mostly related to abrasion and the occasional fence-strike, ropes tend to get
shorter before they wear out completely. Tug-pilots should watch out for this
and refuse to tow with ropes which have become too short, say under 50
metres in length.
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Apart from the short rope of a double-towing pair, a rope shorter than the
minimum length may be used for special purposes. Examples of special
purposes may be for outlanding retrieves (to increase effective field length)
or for towing through extreme turbulence such as wave rotors (to keep both
aircraft in the same airmass). Needless to say, such activities will only be
tackled by tug-pilots of considerable experience and pilots involved in these
activities will be very much on the ball to release the rope at the first sign of
real trouble.
Poly ropes suffer from UV deterioration and tug-pilots should ensure that
ropes are not left outside after flying. A rope left lying around on a Sunday
evening will be considerably weakened by the following Saturday morning.
Rings
As a general rule, Tost rings must be used in Tost releases and Ottfur rings
in Ottfur releases. Either type of ring may be used in the “latch” type release
sometimes found on tug aircraft.
Weak links
Weak links are fitted to aerotow ropes for the protection of both the glider
and the tug. However, there is a problem relating to the permitted weak link
strength for tugs in Australia. Apart from the Piper Pawnee 235, which
specifies a weak link strength of 750 kgs, the Flight Manuals of all other tugs
limit the weak link strength to 450 kgs.
This means that gliders which specify weak link strengths greater than 450
kgs must be satisfied with a weaker link than they really need, in order that
the tug may retain its protection. If a stronger weak link than 450 kgs is fitted
in order to satisfy the glider, the tug’s protection is lost.
This is an unsatisfactory situation for both glider and tug, but up to the time
of publication of this manual, had not been resolved with the Civil Aviation
Safety Authority.
Gliders specifying a weaker link than 450 kgs should insert such a link in
addition to (or instead of) the one already fitted for the tug, in order to
preserve the airworthiness requirements of both aircraft.
If only one weak link is fitted to an aerotow rope, it is normally fitted at the
tug end. This gives adequate protection at both ends of the rope during the
climb (within the limitations described in foregoing paragraphs), but also
retains this protection in the event of the tug inadvertently snagging the rope
on an obstacle on the final approach. Better to break a weak link than pull
the tug out of control.
NOTE: Apart from “Tost” weak links, which are in use by some clubs, the
most common form of weak-link for aerotowing is a small piece of 8mm rope
inserted between the main rope and the rings at the tug end. The nominal
strength of a piece of 8mm with a bowline in it is about 580 kgs, but quality
December 2006
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control on poly ropes is imprecise and there could be wide variations.
Because most of the bulk sales of this rope are to either the fishing or
telecommunications industry (guy ropes), it is commonly over-strength, as
these industries have little interest in weak ropes. Don’t use one of these
weak-links unless you have them pull-tested first. TAFE colleges are useful
places for getting this sort of work done.
For club wishing to use Tost weak links, the available loads, colour codes
and Tost part-numbers are as follows.
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12.
APPENDIX - MISCELLANEOUS INFORMATION AND
STANDARD FORMS
12.1
A TYPICAL GLIDER-TOWING PERFORMANCE CHART
(PAWNEE 235)
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12.2
CUTAWAY OF A TYPICAL TUG ENGINE (LYCOMING 0-540)
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12.3
EXTRACT FROM CIVIL AVIATION REGULATIONS - DAILY
INSPECTION SCHEDULE
SCHEDULE 5 CASA maintenance schedule
(subregulation 2 (1), definition of CASA maintenance schedule)
Part 1—Daily Inspection
1.1 An inspection (in this Part called a daily inspection) must be carried out
on the aircraft before the aircraft’s first flight on each day on which the
aircraft is flown.
1.2 A daily inspection must consist of the making of such of the checks set
out in the table at the end of this Part as are applicable to the aircraft.
TABLE OF CHECKS INCLUDED IN A DAILY INSPECTION
Section 1—General
(1) Check that the ignition switches are off, the mixture control is lean or
cut off, the throttle is closed and the fuel selector is on.
(2) Check that the propeller blades are free from cracks, bends and
detrimental nicks, that the propeller spinner is secure and free from
cracks, that there is no evidence of oil or grease leakage from the
propeller hub or actuating cylinder and that the propeller hub, where
visible, has no evidence of any defect which would prevent safe
operation.
(3) Check that the induction system and all cooling air inlets are free
from obstruction.
(4) Check that the engine, where visible, has no fuel or oil leaks and
that the exhaust system is secure and free from cracks.
(5) Check that the oil quantity is within the limits specified by the
manufacturer for safe operation and that the oil filler cap, dipstick
and inspection panels are secure.
(6) Check that the engine cowlings and cowl flaps are secure.
(7) Check that the landing gear tyres are free from cuts or other
damage, have no plies exposed and, by visual inspection, are
adequately inflated.
(8) Check that the landing gear oleo extensions are within normal static
limits and that the landing gear doors are secure.
(9) Check that the wing and fuselage surfaces are free from damage
and that the inspection panels, flight control surfaces and flight
control devices are secure.
(10) Check that the interplane and centre section struts are free from
damage and that the bracing wires are of the correct tension.
(11) Check that the pitot heads and static ports are free from obstruction
and that the pitot cover is removed or is free to operate.
(12) Check that the fuel tank filler caps, chains, vents and associated
access panels are secure and free from damage.
(13) Check that the empennage surfaces are free from damage and that
the control surfaces control cables and control rods, where visible,
are secure.
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(14) Check that the canard surfaces are free from damage and that the
control surfaces, control cables and control rods, where visible, are
secure.
(15) Check that the flight controls, the trim systems and the high lift
devices operable from the ground have full and free movement in
the correct sense.
(16) Check that the radios and antennae are secure and that where
visible, radio units and interwiring are secure.
(17) Check that the drain holes are free from obstruction.
(18) Check that there is no snow, frost or ice on the wings, tail surfaces,
canards, propeller or windscreen.
(19) Check that each tank sump and fuel filter is free from water and
foreign matter by draining a suitable quantity of fuel into a clean
transparent container.
(20) Check that the windscreen is clean and free from damage.
(21) Check that the instruments are free from damage, legible and
secure.
(22) Check that the seat belts, buckles and inertia reels are free from
damage, secure and functioning correctly.
GFA Note
Add tug related items: e.g. mirrors, tow-release mechanism to this list.
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12.4
EXTRACT FROM CIVIL AVIATION REGULATIONS PERMISSIBLE MAINTENANCE BY PILOTS
SCHEDULE 8
Paragraph 42ZC (4) (d)
MAINTENANCE THAT MAY BE CARRIED OUT ON A CLASS B
AIRCRAFT BY A PILOT ENTITLED TO DO SO UNDER
SUBREGULATION 42ZC (4)
1. Removal or installation of landing gear tyres, but only if the removal or
installation does not involve the complete jacking of the aircraft.
2. Repair of pneumatic tubes of landing gear tyres.
3. Servicing of landing gear wheel bearings.
4. Replacement of defective safety wiring or split pins, but not including
wiring or pins in control systems.
5. Removal or refitting of a door, but only if:
(a) no disassembly of the primary structure or operating system of the
aircraft is involved; and
(b) if the aircraft is to be operated with the door removed—the aircraft
has a flight manual and the manual indicates that the aircraft may
be operated with the door removed.
6. Replacement of side windows in an unpressurised aircraft.
7. Replacement of seats, but only if the replacement does not involve
disassembly of any part of the primary structure of the aircraft.
8. Repairs to the upholstery or decorative furnishings of the interior of the
cabin or cockpit.
9. Replacement of seat belts or harnesses.
10. Replacement or repair of signs and markings.
11. Replacement of bulbs, reflectors, glasses, lenses or lights.
12. Replacement, cleaning, or setting gaps of, spark plugs.
13. Replacement of batteries.
14. Changing oil filters or air filters.
15. Changing or replenishing engine oil or fuel.
16. Lubrication not requiring disassembly or requiring only the removal of
nonstructural parts, or of cover plates, cowlings and fairings.
17. Replenishment of hydraulic fluid.
18. Application of preservative or protective materials, but only if no
disassembly of the primary structure or operating system of the aircraft is
involved.
19. Removal or replacement of equipment used for agricultural purposes.
20. Removal or replacement of glider tow hooks.
21. Carrying out of an inspection under regulation 42G of a flight control
system that has been assembled, adjusted, repaired, modified or
replaced.
22. Carrying out of a daily inspection of an aircraft.
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12.5
COMPETENCE CHECK LIST - INITIAL GLIDER-TOWING
PERMIT
Pilot’s name: .......................................................................................................................
Pilot Licence: Type .............................................. Number: ..............................................
Experience, hours: Aeroplanes (incl.
Ultralights) ............................................................. Gliders ................................................
Gliding Club: ......................................................... .............................................................
Sat - Satisfactory in all respects.
Accept - Room for improvement (specify), does not prevent issue of
rating
NORMAL PROCEDURES
Pre-flight inspection
Assessing take-off performance using published information
Glider speeds and wing-loading variations
Ground-run and take-off
Correct grading of initial climb
Selection of suitable climb-out path
Monitoring mirrors
Positive lookout and clearing aircraft’s blind spots during climb
Accurate attitude control in straight flight and turns
Maintaining steady platform with glider out of position
Executing correct towing pattern, taking into account wind, sun, lift/sink,
airspace requirements and glider pilot’s instructions
Positively confirming release of glider before commencing descent
Correct engine handling during initial descent phase
Positive lookout and clearing aircraft’s blind spots during descent
Maintaining correct IAS and RPM during descent
Correct circuit join, including appropriate radio calls
Normal approach and landing with rope attached
ABNORMAL PROCEDURES
Stop signal during take-off run
Partial power-failure during take-off run
Airbrakes open in flight (rudder waggle)
Emergency release (wing rock)
Cruising on tow
Descending on tow
Landing on tow (optional)
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GENERAL REMARKS
Refer to form of initial glider towing permit
The above-named applicant has been assessed in glider-towing operations in accordance
with the GFA Aerotowing Manual. I have examined the applicant’s logbooks and certify that
he/she has logged the aeronautical experience shown above.
I am satisfied that the applicant has a good understanding of all normal and abnormal
procedures and limitations for glider-towing operations as specified in the GFA Operational
Regulations, the Manual of Standard Procedures and the Aerotowing Manual. I am
satisfied that the applicant has achieved an adequate standard in gliders as far as
aerotowing procedures and skills are concerned.
Signature of CASA delegate:
..............................................................................................................................................
Name (print):
..............................................................................................................................................
Pilot Licence: Type ........................................... Number ..................................................
Permit issued on (date) ......................................................................................................
CASA DELEGATE TO RETAIN THIS ASSESSMENT ON FILE
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12.6
COMPETENCE CHECK LIST - DOUBLE TOWING APPROVAL
Pilot’s name: .......................................................................................................................
Glider-towing experience:
Hours ...................................................................... Launches ............................................
Gliding Club: ......................................................... .............................................................
NOTE: NO IN-FLIGHT ASSESSMENT REQUIRED FOR THIS APPROVAL
Knowledge of basic requirements for double towing
Knowledge of minimum rope-length requirements
Knowledge of pre-takeoff glider placement
Knowledge of all applicable launch emergencies
Received specific briefing prior to carrying out a double tow
Refer to form of further glider towing permit
..............................................................................................................................................
Name (print):
..............................................................................................................................................
Approval issued on (date) ..................................................................................................
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12.7
COMPETENCE CHECKLIST - OUTLANDING RETRIEVE
APPROVAL
Pilot’s name: .......................................................................................................................
Glider-towing experience:
Hours ...................................................................... Launches ............................................
Gliding Club: ......................................................... .............................................................
Sat - Satisfactory in all respects.
Accept - Room for improvement (specify), does not prevent issue of
rating
Knowledge of CAR 92 and CAAP 92-1 with respect to outlanding
retrieves
Demonstration of ability to carry out aerial inspection of a selected
paddock to determine whether or not a glider could be towed from it
Execution of precautionary inspection(s) and dropping rope before
landing
Execution of safe take-off (at home base), towing a glider, without groundcrew and using agreed signals for launch commands
Knowledge of obligations to landowner
Knowledge of daylight/darkness graphs and conversion of arc to time
Demonstration of cruising on tow and knowledge of fuel consumption of
tug/glider combination at cross-country towing speeds
Refer to form of further glider towing permit
Declaration by CASA delegate
The above-named applicant has demonstrated competence in outlanding retrieve
procedures in accordance with the above checklist. I have examined the applicant’s
logbooks and certify that he/she has logged the aeronautical experience shown above and
is considered competent to safely carry out outlanding retrieves.
..............................................................................................................................................
Name (print):
..............................................................................................................................................
Approval issued on (date) ..................................................................................................
CASA DELEGATE TO RETAIN THIS ASSESSMENT ON FILE
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12.8
GLIDER TOWING PERMIT, DOUBLE TOWING AND
OUTLANDING RETRIEVE APPROVALS
Refer to Appendix 1 “Notes for Delegates” for samples of Initial Glider
Towing Permit and Further Glider Towing Permit.
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12.9
CIVIL AVIATION REGULATIONS (CARS) 92 AND 93 - USE OF
AERODROMES
92.
(1) An aircraft shall not land at, or take-off from, any place unless:
(a) The place is an aerodrome, established under the Air
Navigation Regulations; or
(b) The use of a the place as an aerodrome is authorised by a
licence granted under regulation 89C; or
(c) The place is an aerodrome for which an arrangement under
section 20 of the Act is in force and the use of the aerodrome
by aircraft engaged in civil air navigation is authorised by
CASA under that section; or
(d) The place (not being a place referred to in paragraph (a), (b)
or (c) is suitable for use as an aerodrome for the purposes of
the landing and taking off of aircraft;
and, having regard to all the circumstances of the proposed landing or takeoff (including the prevailing weather conditions), the aircraft can land at, or
take-off from, the place in safety.
Penalty: 25 penalty units.
(2) CASA may, in relation to the aerodrome, issue directions relating
to the safety of air navigation.
(3) A person must not contravene a direction.
Penalty: 25 penalty units.
93. Protection of certain rights
Nothing is these regulations shall be construed as conferring on any aircraft,
as against the owner of any land or any person interested therein, the right
to alight on that land, or as prejudicing the rights or remedies of any person
in respect of any injuries to persons or property caused by that aircraft.
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12.10 CIVIL AVIATION ADVISORY PUBLICATION (CAAP) 92-1,
GUIDELINES FOR AEROPLANE LANDING AREAS
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12.11 EXTRACT FROM AERONAUTICAL INFORMATION
PUBLICATION (AIP) - DAYLIGHT/DARKNESS GRAPHS (END
OF DAYLIGHT ONLY)
(GEN 2.7 - 29 JUN 05 - AIP Australia)
1. DAYLIGHT AND DARKNESS GRAPHS
“Night” is that period between the end of evening civil twilight and the beginning of
morning civil twilight. For all intents and purposes, first light should be construed
as the beginning of civil twilight, and last light as the end of civil twilight. The terms
“sunrise” and “sunset” have no relevance when calculating daylight operating
times for the VFR pilot.
To compute the beginning or end of daylight using the graphs contained in this
section:
a. enter the top or bottom of the scale at the appropriate date;
b. move vertically up or down to the curve for the latitude of the place
concerned (interpolating for intermediate latitudes if necessary);
c. move horizontally to the left or right and read local mean time on the vertical
scale at the side;
d. to convert to UTC, subtract (in E longitudes) from the LMT obtained, the time
increment corresponding to the longitude of the place concerned in the
“Conversion of Arc to Time” table.
e. to convert to EST, add 10 hours to UTC;
f. to convert to CST, add 91/2 hours to UTC;
g. to convert to WST, add 8 hours to UTC.
Example: To determine the end of daylight at Echuca
(S36 09.0 E144 46.0) on 20th November.
th
Using the graph, enter at 20 November at the top of the page and follow
downwards to latitude 36° (by interpolation), then horizontally to the left and read
off LMT = 1919. To convert to UTC, enter the “Conversion of Arc to Time” table,
at longitude 144° (9 hours 36 minutes). Add the increment corresponding to 46’
in the right hand column
= 3’ 04” + 0936 = 0939.
Subtract this from the LMT found: 1919 -- 0939 = 0940 UTC.
To find EST add 10 hours to UTC=1940 EST.
Users of these graphs should note that the parameters used in compiling the
Daylight and Darkness Graphs do not include the nature of the terrain
surrounding a location, or the presence of other than a cloudless sky and
unlimited visibility at that location. Consequently, the presence of cloud cover,
poor visibility or high terrain to the west of an aerodrome will cause daylight to
end at a time earlier than that extracted from the appropriate graph. Allowance
should be made for these factors when planning a flight having an ETA near the
end of daylight.
Local Time
Local time in Australia falls into three separate zones:
Eastern Standard Time (EST), which is UTC + 10 hours;
Central Standard Time (CST), UTC + 9½ hours; and
Western Standard Time (WST), UTC + 8 hours.
These times apply as follows:
a. EST is used in the States of New South Wales (except the Broken Hill area),
Queensland, Victoria, Tasmania and the Australian Capital Territory;
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b. CST is used in the State of South Australia, the Northern Territory and the
Broken Hill area; and
c. WST is used in the State of Western Australia.
However, certain States introduce local Summer Time each year between
October of that year and March of the succeeding year, which adds an additional
hour to the local time applicable in that State.
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12.12 CONVERSION OF ARC TO TIME
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12.13 CROSSWIND COMPONENT CHART
In this example, a wind of 25 knots at 30º to the strip gives a headwind
component of 22 knots and a crosswind component of 12 knots.
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13.
SELF-TEST QUESTIONS AND ANSWERS
13.1
GLIDER-TOWING PERMIT – QUESTIONS
1.
What are the minimum experience requirements for a person to be
considered as (a) a tug-pilot and (b) a CAR 149 delegate for glider
towing?
2.
What is the period of validity of a glider-towing permit?
3.
What are the pilot recency requirements for a Glider Towing Permit?
4.
Name the privileges and limitations of a glider-towing permit that has no
particular approvals added to it.
5.
What can the holder of a Permit including outlanding retrieve approval
do that the holder of a glider-towing permit cannot?
6.
Can a pilot who holds a glider-towing permit which does not include
outlanding retrieve approval carry out a cross-country tow between two
aerodromes?
7.
Can a CAR 149 delegate’s authority be renewed if the recency
requirements of a glider-towing permit are not met?
8.
When referring to “high-tow” and “low-tow”, what is the reference?
9.
Can the holder of a glider-towing permit carry out double towing?
10. What is the minimum rope length for towing a single glider?
11. What is the maximum breaking strength for tug weak-links and what
action would you take if towing a glider which specified a weak-link of
lower breaking strength than the tug’s standard?
12. Is it a requirement to have at least one mirror on a tug?
13. Is it permissible to tow a glider with an aircraft which does not have a
performance chart for glider-towing?
14. What is the signal to a glider pilot which indicates that the rate of climb
is abnormally low and everything appears to be in order at the tug end?
What is the usual cause of such a low climb-rate?
15. What pre-takeoff and pre-landing checks apply to glider tugs?
16. Name the three signals for take-up-slack, all-out (full-power) and stop.
Who is authorised to give these signals to a tug aircraft?
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17. At what pace should the tug-pilot take up the slack in the rope, and
why?
18. If you are towing with a taildragger, what precaution would you take
against the rope breaking when making the transition between take-upslack and all-out?
19. What is likely to happen to the glider if the tug-pilot holds the tug down
close to the ground, then rotates rapidly into the climb?
20. What is the primary reference for maintaining a steady climb?
21. What is the most important point of airmanship to remember during the
climb?
22. Name two important points of flying skill which make station-keeping
much easier for glider-pilots.
23. Under what circumstances is it permissible to lean the mixture control
when towing?
24. Under what circumstances would a glider be towed downwind?
25. What precautions must always be taken before beginning a descent off
tow?
26. What is the emergency “wave-off” signal and what must a tug-pilot do
to ensure that a clear, unambiguous signal is given?
27. What is the “glider unable to release” signal and what particular
precaution must be taken by the tug-pilot while the glider-pilot is making
the signal?
28. Name two standard procedures to be followed when searching for other
aircraft when climbing or descending.
29. What is likely to occur during a descent at moderate power in
conditions of cool temperature (< 15ºC) and fairly high humidity (e.g.
quite a lot of cloud)?
30. What is the rather unusual characteristic exhibited by a rope after it has
been dropped from a tug?
31. Are glider tugs exempt from compliance with CTAF/ CTAF<R>
procedures?
32. What particular problem is associated with the power-off final approach
usually practised by glider tugs and what precautions are necessary to
counter it?
33. What glider limitation does a tug-pilot need to know before attempting a
cross-country tow?
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34. What action is the tug-pilot required to take on receipt of a “stop” signal
(a) early in the take-off run and (b) later in the take-off run?
35. What is the first priority if the tug suffers partial or complete engine
failure in flight?
36. For the purpose of getting back to the airfield, by how much is the
gliding range of the average training glider reduced if it is towed
downwind?
37. What is a “practice wave-off”?
38. When carrying out a landing on tow, what braking procedure is adopted
by the tug-pilot on the ground-roll after landing?
39. How much height is consumed in recovering from a “tug upset”?
40. Apart from usual things like the correct oil quantity, what item is of
particular importance when checking under the cowling during the daily
inspection of a glider tug?
41. At what rate does cooling of an air-cooled engine vary with respect to
airspeed and what is the maximum allowable rate of change of
temperature during a descent (Lycoming engines)?
42. Does a glider-tug have an exemption from the requirement to have the
wings level on final approach for a minimum horizontal distance of 500
metres?
43. What is the form of post-release descent that is NEVER acceptable?
44. What is the most likely problem to be experienced if Mogas is used
instead of Avgas?
45. How much of the original rope strength is retained if a bowline is used
to secure the rings or repair a rope?
46. What kind of rings are permitted to be used (a) on the glider end and
(b) on the tug end?
47. For what special purposes may a rope shorter than the standard length
be used and what precaution should an operator take in permitting
such a rope to be used?
48. Who is the pilot-in-command of a tug/glider combination?
49. Who gives way to whom in the case of a conflict between a powered
aircraft and a tug/glider combination?
50. If a tug engine runs roughly after start-up, then after a few seconds
smoothes out and runs normally, what problem should you suspect and
what should you do?
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51. What effect can be expected when aerotowing in conditions of high
humidity?
52. As a rule of thumb, what increase in take-off run can be expected with
an increase in density altitude?
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13.2
GLIDER TOWING PERMIT – ANSWERS
1.
(a) Private or higher licence, with 100 hours total aeronautical
experience, at least 40 hours on VH-registered powered aircraft, the
remainder of which may include gliders and three-axis control
ultralights. (b) 175 hours total aeronautical experience, at least 100 of
which shall be on aeroplanes, with a minimum of 50 hours glider-towing
experience and having held glider-towing approval, including outlanding
retrieve approval, for at least twelve months.
2.
Indefinite, as long as the pilot’s licence remains valid and the recency
requirements are met.
3.
At least ten flights as pilot-in-command of an aeroplane towing a glider
in the preceding six months or be assessed as competent by a CASA
delegate.
4.
May act as pilot-in-command in glider towing operations in VMC , from
a licensed aerodrome or from an established and suitably marked
gliding site approved by the GFA and which meets the requirements of
an Aircraft Landing Area.
5.
Land in and carry out outlanding retrieves from unmarked paddocks.
6.
Yes, with the provisos that the pilot’s licence must not have an area
restriction and the aerodromes must be marked aerodromes or
approved gliding sites.
7.
No.
8.
The slipstream.
9.
Not unless the pilot holds a Permit which includes double tow approval.
10. 55 metres.
11. 450 kgs, except for the Pawnee 235, which is 750 kgs. If a glider
needs a lower weak-link strength than these figures, a separate weak
link has to be fitted for the purpose.
12. Yes.
13. Yes, but it must have a towing supplement to prove that it is approved
for glider-towing.
14. A rudder-waggle, usually caused by the glider’s airbrakes (or possibly
tail-chute) coming open during the tow.
15. Normal everyday checks, otherwise there is a danger of missing
something.
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16. “Take-up-slack”: underarm wave.
“All out (full-power)”: overarm
wave. These two signals may only be given by authorised signallers.
“Stop”: one or both hands held stationary above the head. This signal
may be given by anyone at the launch point.
17. Very slowly, to avoid the risk of jerking the glider forward and causing
an over-run.
18. Do not use forward stick during this transition, or the tug will tip on its
nose if the rope breaks.
19. Slack will develop in the rope and it will almost certainly break when it
pulls tight again.
20. The nose attitude.
21. To constantly clear all the aircraft’s blind spots.
22. Maintain a constant nose attitude and keep the slip/skid ball in the
middle.
23. Only to prevent rough running due to density-altitude problems.
24. At the request of the pilot or for the purpose of avoiding terrain or
controlled airspace.
25. Always make a visual check that the rope has released from the glider.
Do not rely on feeling a jerk in the rope, nor on a radio transmission.
Always ensure the airspace you are about to occupy is clear before
descending into it.
26. Rocking the wings, ensuring full aileron/rudder coordination to avoid
residual adverse yaw.
27. The glider pilot flies out to the left of the tug and awaits
acknowledgement by the tug pilot. The tug pilot must ensure that the
tug is not yawed by the glider and that a constant heading is
maintained during the manoeuvre.
28. Carry out a head-count of known traffic. Use shadows to assist in
locating traffic.
29. Carburettor icing.
30. It loses forward speed very quickly and falls almost vertically.
31. No.
32. The high rate of descent increases the risk of collision with another
aircraft underneath the tug. Check carefully for traffic during final turn
and throughout the approach.
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33. The glider’s maximum aerotow speed.
34. (a) Release glider, keep moving, do not brake suddenly. (b) Release
glider, consider option of taking off to clear the strip. Always assume
that you might get a stop signal on every launch.
35. Get rid of the glider.
36. By two-thirds, i.e. it has only one-third of the range it would have if it
had been towed into-wind.
37. There is no such thing as a practice wave-off.
38. Do not use the brakes at all, let the glider bring the combination to a
stop, unless there has been a gross misjudgement of the landing and
you are running out of strip fast, in which case self-preservation will
guide you to turn off and brake rather than have a colossal pile-up
against the far fence.
39. A minimum of 800 feet.
40. The condition of the cooling baffles.
41. Approximately as the square of the airspeed. 50ºF per minute.
42. No.
43. The aerobatic “half-roll and pull-through”.
44. Vapour-locking on warm days.
45. About 85%.
46. (a) Tost rings ONLY. (b) Tost or Ottfur rings.
47. For towing out of paddocks or for “rotor” conditions during wavesoaring, only by pilots of considerable experience.
48. The tug-pilot.
49. The powered aircraft should give way to the combination. However it is
worth remembering that all pilots are responsible for taking action to
avoid an impending collision.
50. Sticking valve or valves. This problem is unlikely to go away and
continued operation could result in serious damage, such as bent
pushrods, resulting in failure. Have the engine inspected without
further delay.
51. A loss of power, as high moisture content in the air means effectively
less air entering the engine. An additional problem is that the amount
of moisture varies with the temperature of the air, probably more than
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you might imagine. For example, air at 35ºC holds eight times the
amount of moisture as air at 5ºC. You are going to lose a lot of
performance in humid, tropical conditions.
52. Approximately 25% increase in take-off run for every 1,000 feet
increase in density altitude, in other words double the take-off distance
for an increase in density altitude of 4,000 feet. Such density altitude
figures are common in Australia in summer. Know how to twiddle your
“prayer-wheel” and get the answers, especially for an outlanding
retrieve!
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13.3
DOUBLE TOWING APPROVAL – QUESTIONS
1.
What are the requirements which must be met before double towing
may take place?
2.
What are the minimum rope lengths to be used for double towing?
3.
If the ropes are attached to the tug in such a way that they will not
necessarily separate after release by the tug-pilot, does this prevent a
double tow from taking place?
4.
Prior to take-off, in light crosswinds, how would you ensure the
placement of the short-rope glider in relation to the tug, and why?
5.
What would you do if asked to carry out a double tow in a strong
crosswind?
6.
Which glider should the pilot of greater experience fly, and why?
7.
What is the earliest point in a double tow at which the tug-pilot may
start a turn?
8.
In normal circumstances, which glider releases first from a double tow?
9.
If the glider on the short rope flies out to the left and remains in that
position, what does this mean and what action should you take?
10. What action should you take if you follow the procedure in answer No
9, but the long-rope glider does not release and more than 10 seconds
have elapsed since the return of the short-rope glider to the high-tow,
line-astern position?
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13.4
DOUBLE TOWING APPROVAL – ANSWERS
1.
There must be adequate strip length, width and obstacle clearance for
the entire combination to be safe. Wingtip holder must be positioned at
outer wings. Forward signaller essential and water ballast must not be
carried.
2.
35 metres for the short rope and 65 metres for the long rope.
3.
No. It is desirable to arrange for the ropes to separate after release,
but it is not possible on all release-hook installations and, even on
those in which it is possible, the reliability is not known. Therefore
double tows may be carried out with the ropes meeting at a common
ring-pair prior to attachment to the tug.
4.
The short-rope glider should be placed on the upwind side of the tug, to
avoid the possibility of a ground-loop endangering the long-rope glider.
5.
It would be wise to refuse to carry out a double tow in a strong
crosswind.
6.
The more-experienced pilot should fly the glider on the long rope, in
case of a problem with the short-rope glider on take-off, such as a rope
break or ground-loop, which needs a rapid reaction and precisely the
right actions to prevent a ground-collision.
7.
Not before both gliders have settled into the line-astern position.
8.
The one on the short rope.
9.
It means the same as on a single tow, that the glider pilot has tried to
release and is unable to do so. The tug pilot’s required action is to
(a) acknowledge the glider pilot’s predicament in the normal manner,
whereupon it will return to its high-tow, line-astern position and
(b) wait until the long-rope glider has released and cleared, then
release the short-rope glider from the tug.
10. You should assume that the long-rope glider is also unable to release
and accordingly you should release the ropes at the tug end without
further delay.
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13.5
OUTLANDING RETRIEVE APPROVAL – QUESTIONS
1.
What is the first requirement before you even consider setting out on an
aerotow retrieve?
2.
What cues are available to assess the wind at the outlanding paddock
without the assistance of a windsock?
3.
Are you obliged to go ahead with the aerotow retrieve if the paddock in
which the glider has landed is not suitable for the purpose?
4.
What is the glider pilot’s “Five S” rule for outlanding?
5.
What would be your plan if the selected paddock has discernible slope
along the landing/ take-off path?
6.
If the paddock size seems marginal, what option is available to
effectively increase its size?
7.
What are SWER lines and what precautions should be taken to
minimise the hazard caused by them?
8.
What are the implications of side-slope on landing and take-off?
9.
What would you do with the rope before setting out on an aerotow
retrieve?
10. What is the most essential job to do before attempting an aerotow takeoff from a paddock?
11. What is the effect of long grass and what precautions would you take?
12. Under what circumstances would an aerotow retrieve be permissible on
a day of total fire ban?
13. What would you do if there were clumps of long grass and no wingtip
holder to assist in the paddock take-off?
14. What are the implications of landing at or taking off from a paddock in
the lee of a hill?
15. What six words should a tug-pilot keep in mind when asked to do an
outlanding retrieve?
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13.6
OUTLANDING RETRIEVE APPROVAL – ANSWERS
1.
Obtain the permission of the owner of the paddock.
2.
Water on dams (especially wind-shadow), dust from cars on dirt roads,
assessing aircraft drift.
3.
No.
4.
Size, slope, surface, stock, surroundings.
5.
Plan on landing up the slope and taking-off down the slope.
6.
Use it corner-to-corner, all other things being satisfactory.
7.
Single Wire Earth Return. Do not land until you have located them all.
Every homestead has at least one SWER line and there may be more
than one if there are outbuildings on the property. You MUST find them
all.
8.
Even if side-slope falls within the guidelines of CAAP 92-1, it may still
be too much for the glider you are going to tow, especially if it is an
Open-Class type with over 20 metre wingspan.
9.
Remove it or drop it before landing. If you remove it, don’t forget to
stow it in the aircraft! Don’t land in a paddock with a rope attached.
10. Pace out the distance available and carefully check the surface and
surrounds.
11. Know your aircraft’s performance, either from experience or from the P
Chart. If grass is marginal but just acceptable, ensure you have a
properly briefed wingtip holder.
12. Only if the glider has landed at a designated aerodrome (i.e. listed in
the “ERSA” document). If the glider is in a paddock, it is not
permissible to attempt an aerotow retrieve.
13. It would be wise to refuse to take off.
14. Downwash, which will adversely affect climb performance after
separation.
15. If in doubt, get the trailer.
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FINAL REMINDER
GLIDER-TOWING DEMANDS THE HIGHEST QUALITY
OF SKILL, KNOWLEDGE AND, ABOVE ALL,
AIRMANSHIP
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NOTES FOR DELEGATES
(provided by the Civil Aviation Safety Authority)
What is an Instrument of Delegation?
An Instrument of Delegation is used by CASA to transfer its legal powers and
functions under the Civil Aviation Act 1988 or the Civil Aviation Regulations 1988
(CAR 1988) to an individual. The Instrument is issued by the Director of Aviation
Safety signing a legal document under regulation 7 of CAR 1988 appointing a person
as a delegate for the exercise of CASA’s powers and functions under a particular
regulation or regulations. The delegation is tied to those particular powers and
functions, and is usually issued for a set period of time stated in the instrument.
By delegating certain powers and functions to members of the aviation industry,
CASA can remove the need for staff to deal with routine matters that are more
efficiently handled by the industry, whilst ensuring that only those people with the
required specialist knowledge and skills are able to make these decisions.
How CASA delegates its powers
Delegations are issued in accordance with regulation 7 of CAR 1988, which states:
7
Delegation by CASA
1.
2.
3.
The Director may, in writing, delegate to a person all or any of
CASA’s powers and functions under CAR.
A delegation may be made subject to conditions that are necessary
in the interests of the safety of air navigation.
A delegate is subject to any written direction of the director in the
exercise of a power, or the performance of a function, delegated
under subregulation (1).
The Director can issue limitations on the exercise of the delegation – for instance to
limit it to the issuing of permissions to tow gliders rather than any other things – and
to give directions such as the form in which the delegate can issue the permissions
or the general manner in which instructions are issued or the experience and
competency levels of person to whom the permissions and directions can be issued.
These limitations and directions must be issued in writing and normally form part of
the Instrument of Delegation.
Forms for the initial and further glider towing permissions are attached. In the
numbering system, each permission is identified by the year of issue (2 digits), the
sequence number for the delegate, starting at 01 each year (2 digits), and the
Aviation Reference Number of the Delegate (6 digits).
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Regulations for glider towing activities – powers delegated
The Civil Aviation Regulations that are relevant to towing gliders are regulations 149
and 150 of CAR 1988. The applicable words are:
149
Towing
(1) Subject to this regulation, the pilot in command of an aircraft in flight
shall not permit anything to be towed by such aircraft except with the
permission of CASA and in accordance with CASA’s directions.
Penalty: 50 penalty units
…
(4) An offence against subregulation (1) is an offence of strict liability.
…
(5) It is a defence to a prosecution under subregulation (1) if:
(a)
the pilot in command had the written permission of CASA for the
towing; and
(b)
the towing was done in accordance with the directions (if any)
specified in the permission.
150
Dropping of articles
(2) Subject to this regulation, the pilot in command of an aircraft in flight
shall not permit anything to be dropped from the aircraft.
Penalty: 25 penalty units
(1A) An offence against subregulation (1) is an offence of strict liability.
(3) Nothing in this regulation shall prevent:
(a) the dropping of packages or other articles or substances:
(i) in the course of agricultural operations; or
(ii) in the course of cloud seeding operations; or
(iii) in the course of firefighting operations; or
(iv) to initiate controlled burning; or
(v) in the course of search and rescue operations; or
(vi) to deliver emergency medical supplies; or
(vii) to deliver emergency food supplies; or
(viii) in the course of other operations;
in accordance with directions issued by CASA;
(ix) to ensure the safety of the aircraft as far as practicable; and
(x) to minimise hazard to persons, animals and property;
….
Delegates are thus appointed to give permission to the holder of a flight crew licence
to act as pilot in command of an aircraft towing things (gliders) and to issue
directions as to how this is to be done (CAR 149) and to give safety directions under
CAR 150 for the dropping of tow ropes.
Strict Liability means that there is no requirement for a prosecution to show any
intent to break the rule – the fact that the person did whatever act was unlawful and
that there are no circumstances that would make it lawful, are sufficient. So a pilot
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who tows anything and/or drops a towing device must be able to show that he or she
was permitted by CASA (i.e. a delegate, one of you) and he or she did the act in
accordance with CASA’s instructions.
This explains why the permission must be in the form approved by CASA and why
CASA must be given a copy of the permission within a short time after it is given.
Who is appointed as a Delegate
In the case of glider towing, CASA will normally accept the recommendations of the
GFA as to the suitability of a person to be issued with the delegation to permit pilots
to tow gliders. Such delegates should be pilots with significant experience in glider
towing, who have held a towing permission authorising all relevant towing activities
for a considerable time, and who have a suitable background in the assessing of
skills held by pilots who wish to apply for a towing permission. This usually implies a
background in either flight instruction or airline checking and training, though tug
pilots with other instructional or assessment skills (such as experienced gliding
instructors) may be deemed suitable to carry out this task. Gliding Clubs seeking to
have a particular person appointed as a delegate for glider towing should approach
the GFA office.
The potential delegate will also usually be known to, and accepted by, the local Field
Office of CASA.
Responsibilities of Delegates
Delegates are required to use their specialist experience and judgment when
exercising the delegated powers. To arrive at decisions, delegates must take into
account all pertinent factors, including the policy of CASA. However, they must
arrive at their decision themselves and cannot be directed or instructed by other
persons to come to a particular conclusion or to decide matters a particular way
(subject to subregulation 7(3) of CAR 1988).
Their decisions carry the same authority and liability as decisions made by delegates
who are CASA employees. A delegate is personally liable for his or her decisions.
Glider towing delegates
Delegations issued for the purposes of issuing glider towing permissions include the
limitation or qualifying condition of “...in accordance with the GFA Aerotowing
Manual”. This guides them as to the criteria and competencies to use to assess an
applicant for a towing permission, and the words they should use to issue the
permission.
Before issuing a towing permission the delegate must check that the applicant’s
licence is current – i.e. is supported by a current medical certificate and a flight
review conducted in the preceding 2 years by a flight instructor or CASA appointee
December 2006
96
For the purpose of maintaining CASA’s records of flight crew licence holders,
delegates must send CASA a copy of the permissions that they have granted on
CASA’s behalf. This must be done without any undue delay –within a week.
It is not necessary to report to CASA where a permission holder has satisfied the
delegate of their ongoing competency to tow gliders, but the fact should be
annotated in the permit holder’s personal log book against the flight that was
conducted for that purpose, with a date and signature and the delegate’s Aviation
Reference Number.
December 2006
97
Form of initial glider towing permission
INSTRUMENT NUMBER: ..…/…../………...
<YR/NO/DELARN (e.g. 05/02/123456)>
CIVIL AVIATION ACT 1988
CIVIL AVIATION REGULATIONS 1988
GLIDER TOWING PERMISSION
I, ……………………………………………, a delegate of CASA, under subregulations
149(5) and 150(2) of the Civil Aviation Regulations 1988, give permission to
…………………………………………………….,
(Aviation
Reference
Number
……………….) to act as pilot in command of an aircraft whilst it is towing a glider and
to drop a tow rope and fittings used with a tow rope, on condition that:
a) all towing is to be conducted in accordance with the document titled the GFA
Aerotowing Manual, as agreed by CASA from time to time; and
b) if the holder of this permission has not exercised the privileges of this
permission by towing a glider on ten or more occasions in the six months
preceding the date of a flight, he or she may only exercise those privileges
under the direct supervision of a person who holds a delegation under
subregulation 149(5) until that delegate has attested to his or her competency
by means of an endorsement in his or her personal log book; and
c) he or she must, if dropping a tow rope and fittings used with a tow rope, do so
in a manner and location, and from such a height, that will ensure the safety
of the aircraft as far as practicable; and minimise hazard to persons, animals
and property; and
d) unless specifically authorised by a further glider towing permission, the holder
must not tow more than one glider at a time, nor tow a glider from other than
an established and permanently marked aerodrome that complies with CAAP
92-1, or a gliding field approved for aerotow operations by the GFA.
Signed
Delegate of the Civil Aviation Safety Authority
Printed Name ……………………………………….……ARN …………..……
Date: ……………………………….
December 2006
98
Form of further glider towing permission
INSTRUMENT NUMBER: ….../….../……..…
<YR/NO/DELARN (e.g. 05/03/123456)>
CIVIL AVIATION ACT 1988
CIVIL AVIATION REGULATIONS 1988
GLIDER TOWING PERMISSION
(1) I, ……………………………………………..., a delegate of CASA, under
subregulations 149(5) and 150(2) of the Civil Aviation Regulations 1988 (CAR
1988), give permission to ………………………………………… (Aviation
Reference Number ……………….) to act as pilot in command of an aircraft whilst
it is towing a glider in the additional circumstances listed below, and direct that:
a) all towing is to be conducted in accordance with the document titled the GFA
Aerotowing Manual, as agreed by CASA from time to time; and
b) if the holder of this permission has not exercised the privileges of this permit
by towing a glider on ten or more occasions in the six months preceding the
date of a flight, he or she may only exercise those privileges under the direct
supervision of a person who holds a delegation under subregulation 149(5)
until that delegate has attested to his or her competency by means of an
endorsement in his or her personal log book; and
c) he or she must, if dropping a rope and fittings used for towing a glider, do so
in a manner and location, and from such a height, that will ensure the safety
of the aircraft as far as practicable; and minimise hazard to persons, animals
and property.
(2) The additional circumstances are:
a) towing a glider from an unmarked area that complies with
paragraph 92 (1)(d) of CAR 1998; and
b) towing more than one glider at a time
Note: if only one of these activities is authorised, delegates should omit
the other.
Signed …………………………….
Delegate of the Civil Aviation Safety Authority
Printed Name……………………………..………………ARN ………..…………
Date: ……………………………….
December 2006
99
Form of delegation
INSTRUMENT NUMBER: CASA 237/05
I, WILLIAM BRUCE BYRON, Director of Aviation Safety, on behalf of CASA, make this
instrument under regulation 7 of the Civil Aviation Regulations 1988 (CAR 1988).
Bruce Byron
Director of Aviation Safety and
Chief Executive Officer
30 June 2005
Delegation – Issue of glider towing permissions
1
Duration
This instrument
(a)
(b)
2
commences on 1 July 2005; and
stops having effect at the earlier of:
(i) for each delegate – the delegate ceasing to hold a glider towing
permission; or
(ii) the end of June 2008.
Delegation
I delegate to each person mentioned in Schedule 1 CASA’s powers and
functions under each provision of CAR mentioned in Schedule 2; subject to:
(a) the limitations mentioned in Schedule 2 for the provision; and
(b) the conditions mentioned in Schedule 3.
Schedule 1
Name
Delegates
Aviation Reference Number
[The original instrument CASA 237/05 lists 35 delegates]
December 2006
100
Schedule 2
CAR 1988 provisions and limitations
Provision
Limitation
Subregulation
149 (5)
Limited to:
(a) giving permission to the holder of a current flight crew
licence while acting as pilot in command of an aircraft; to tow
a glider: and
(b) issuing directions relating to towing a glider.
Subregulation
150 (2)
Limited to issuing directions for dropping ropes and fittings
used for towing a glider
Schedule 3
Conditions
1
A delegate must exercise the powers and functions only in accordance
with procedures acceptable to CASA as set out in the GFA Aerotowing
Manual ( GFA Manual ).
2
A delegate must only give a permission or issue a direction in a form
acceptable to CASA as set out in the GFA Manual.
3
A delegate must give CASA, within 7 days after giving a permission or
issuing a direction, a copy of the permission or direction.
4
A delegate must not exercise the powers and functions while only able to
exercise the privileges of his or her glider towing permission under direct
supervision.
December 2006

GFA Aerotowing Manual

Transcription

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