The TBM Avenger Powered Gun Turret

M ARCH - A PRIL 2012
HONORING AMERICAN MILITARY AVIATION THROUGH FLIGHT, EXHIBITION AND REMEMBRANCE
The TBM Avenger Powered Gun Turret
By Col Denis Godfrey
RMW Public Information Officer
Among its many distinctions, the Grumman
“Avenger” was the only
U.S. carrier born aircraft
ever, to carry a powered
gun turret. The only other
powered turrets in Navy
inventory were aboard sea
planes and land based patrol aircraft. The Avenger
was also the only Navy
carrier bomber of that era
to employ a .50 caliber
machine gun as a flexible
defensive weapon. The
Helldiver and SBD
used .30 caliber guns. The
150SE was also the only
production turret ever designed by an airframe
manufacturer, Grumman.
If that’s not enough the
150SE was the only American powered turret to have
one gun.
Pre-war, the Navy wanted
to move away from radio
operators doubling as gunners and specified an enclosed, powered turret for
the XTBF-1. Although in
development at the same
time, Curtiss Aircraft was
unsuccessful finding a
suitable turret for the
XSB2C, “Helldiver”. But
the engineers at Grumman
decided to design their
own turret.
The turret itself is a marvel
of electro-mechanical engineering from the days of
slide-rules and vacuum
tubes. The only computer it
utilized was the standard
issue M1A1 brain usually
installed in an Aviation Machinist’s Mate; preferably of
small stature. If you’ve ever
sat in the turret, you know
what a tight fit it is. Now
imagine sitting there in a
fetal position with your feet
resting on the armor plate
and that machine gun hammering away inches from
your head. That’s the combat
position for the gunner since
the 150SE is a ball turret and
can azimuth 360° and point
the gun barrel nearly vertical.
Movement of the turret is
controlled by the gunner via
a joystick that commands
electric motors for elevation
and azimuth. The motors
receive power from two big
Amplidyne motor/generators
mounted starboard next to
the machine gun. Straight
24VDC would only operate
the turret when static. Introduce the G forces of combat
flying and the motors don’t
have the umph to move the
turret. Therefore, the Amplidyne’s condition the power
and boost it as needed. Larger turrets simply utilize hydraulic motors to overcome
this problem. The joystick
has a “high speed” button to
move the turret quickly to
engage a target. In addition
to the joystick, the control
box has a handhold that
functions as a “deadman”
switch that automatically
returns the turret to a neutral
position if the gunner lets go
of it.
Now to address the question
we all get from folks at airshows; “how do you keep
from shooting the tail off?”
This is the complex part of
the turret mechanism. Obviously you can’t expect a
Continued on page 6
I NSIDE THIS ISSUE :
2012 RMW A IR
S HOW S CHEDULE
2
Help Wanted
2
M AINTENANCE
R EPORT
3
New RMWCAF
CADET
4
W ING L EADER ’ S
R EPORT
4
S TAFF O FFICERS
5
WHAT STARTED IT
ALL?
5
AIRSHO 2012
7
HONORING AMERICAN MILITARY AVIATION THROUGH FLIGHT, EXHIBITION AND REMEMBRANCE
M ARCH - A PRIL 2012
P AGE 2
RMW AIR SHOW SCHEDULE - 2012
MONTH
DAYS
Apr
14th – 15th
May
18th
↓
26th - 27th
Jun
16th
Jul
LOCATION
SHOW
TBM
CUB
STATUS
Tucson, AZ Davis
Monthan AFB
Thunder and Lightning
over AZ w/ T-Birds.
██
Confirmed
USAF Academy
2012 Graduation Week
Begins
██
Pending
Ogden, UT
Hill AFB Open House w/
Thunderbirds.
██
Pending
Boulder, CO
Open House & Dance
██
Confirmed
13th - 14th
Rifle, CO
Garfield Co Air Show
██
↓
28th - 29th
Twin Falls, ID
Air Magic Valley Air Show
w/ Blue Angles
██
Confirmed
Aug
17th - 18th
Powell, WY
Wings 'N' Wheels Classic
Cars & Air Show
██
Confirmed
↓
24th -286h
RMMA, Broomfield,
CO
Colorado Sport Int. Air
Show
██
Confirmed
Sep
1st – 3rd
Steamboat Springs,
CO
Wild West Air Fest
██
↓
15th
Farmington, NM
Rotary Air Show
██
↓
22nd –
23rd
Grand Junction, CO
Gunfighters Skies w/Blue
Angles
██
Oct
10th
Tucumcari, NM
Rotary Club AS
██
Pending
↓
13th - 14th
Midland, TX
AIRSHO - CAF
██
Confirmed
↓
20th- 21st
El Paso, TX
AMIGO Air Show w/ Thunderbirds
██
Pending
██
██
Confirmed
Confirmed
??
██
Confirmed
2012 Air Show Season
Bill Marvel and his wicked
wrench wranglers continue
to put what they hope will
be finishing touches on
‘309’ to have it ready for
our first Air Show appearance of the season - Thunder and Lightning over AZ
at Davis Monthan AFB near
Tucson.
Col Bob Thompson says we
need a couple more crew
members for this show (see
Col Thompson’s Help Wanted Ad above)
If you’ve never had the opportunity to visit the Air
Force Museum at the Davis
Montham AFB aircraft boneyard, you should go to this
show. The Davis Montham
Museum is second only to
the Air Force’s Flagship
Museum at Wright—
Patterson AFB near Dayton,
Ohio. Sign up and help us
“Keep ‘em Flying”.
4,400 aircraft and 13 aerospace vehicles from the Air
Force, Navy-Marine Corps, Army, Coast Guard, and several federal agencies including NASA.
M ARCH - A PRIL 2012
HONORING AMERICAN MILITARY AVIATION THROUGH FLIGHT, EXHIBITION AND REMEMBRANCE
P AGE 3
Maintenance Report - The Wake Up Call
By Col Bill Marvel
Maintenance Officer
At some point in late winter
or early spring every year,
silence at the CAF hangar is
broken by the rumble, smoke
and spitting oil of the TBM
engine once again coming to
life after a long hibernation.
This event is always of interest and especially so when
bystanders are aware three
cylinders have been changed
and the opportunity to see
disintegrating engine parts
being scattered all over the
ramp is real.
Well, once again they were
disappointed as the belching
beast came to life on March 3
and remained intact as it does
every year. That said, it still
wasn’t a happy engine, dripping oil from both the left
and right sides and running a
bit rough after the initial start.
Multiple starts and stops,
with interim oil cleanup to
aid in leak detection, gradually got things partly under
control. Col Rob Duncan in
the cockpit was able to lean
the engine to clean spark
plugs which were partly
fouled by oil coming through
the newly overhauled and not
yet broken in cylinders. Engine smoothness returned as a
result. Multiple sets of eyeballs and pointing fingers
identified some apparent oil
leaks, the worst of which
resulted from a defective
clamp on one of the pushrod
shroud tubes. That was easily replaced and eliminated
one leak. But two remained
at the end of the day – one on
the left side that is coming
through an exhaust port and
one on the right that still con-
founds us and remains to be
identified. Further investigation of the left side leak revealed a subtlety new to us.
All of our cylinders have a
small component called an
exhaust port liner pressed
into their exhaust ports to
repair damage from prior
deterioration. Close inspection resulted the oil leaking
cylinder did not have this
component installed. That
cylinder had been replaced
in Arizona last year and we
had not seen it with the exhaust off until recently so we
were not aware of the missing part. The recommended
fix from an experienced engine shop -- remove the exhaust on that side of the engine and install a gasket on
the cylinder in question.
That’s a simple concept but a
many hour project. Fortunately, yours truly wrote up
a comprehensive step by step
procedure for exhaust removal and installation which
completely eliminates the
mystery and corresponding
need to figure it out again
every year or two. However,
the problem got worse. Removal of the exhaust revealed not only no exhaust
port liner but also that the
serial number on the problem cylinder was not as the
same as on the paperwork
that came with it. We thus
have no idea what repairs
were done or where it came
from, not to mention anything authorizing its being
on the aircraft. Furthermore,
it is the one that is badly
leaking oil. This cylinder
was installed last May in
Arizona by a local shop, now
out of business, that supposedly “overhauled” it. Given
the amount of oil leaking
from the exhaust port, and
seeing it come from the exhaust valve guide, is pretty
good evidence that the guide
was never replaced and is
worn beyond limits. The real
problem is that to change this
cylinder involves removing
the oil cooler, which makes it
a much more difficult job.
On Saturday we’ll do some
checks to determine the extent of valve guide wear but I
am not optimistic.
Despite all the hydraulics
having worked properly
when tested during the first
start, we opted to do a second
check prior to putting the
plane back in the hangar at
the end of the day. It wasn’t
long before many waving
hands and much pointing
caused an early shutdown
of the engine. Red hydraulic fluid coated the right
side bomb bay door and
since we had done a good
deal of work in there replacing hydraulic lines and
clamps, we all wondered
what had occurred. It turns
out an aluminum hydraulic
line installed in the wing
fold/spread circuit was
leaking at a connection.
Further testing revealed no
improvement after tightening the fitting, so it was
disassembled. To our great
surprise, it was immediately apparent a necessary
(Continued on page 7)
The leaking exhaust port on the number 9 cylinder.
WWII Maintenance
M ARCH - A PRIL 2012
HONORING AMERICAN MILITARY AVIATION THROUGH FLIGHT, EXHIBITION AND REMEMBRANCE
P AGE 4
This poster was
an advertisement
for the Citizens
Service Corps part of the local
defense operations within the
US boundaries
during WWII.
Primary Business Address
PO Box 4125
Grand Junction, CO 81502
“What did you do
today
Propwash Gazette Editor
Col Tom Howe
Phone: 970-872-7373
Fax: 970-872-7474
Email: howet@tds.net
...for Freedom?”
RMWCAF on the Web
www.rmwcaf.org
A question we
should be asking
ourselves in these
somewhat peaceful times. Freedom is always
under attack it
seems.
“KEEP 'EM FLYING"
NEW RMWCAF CADET
WING LEADER’S REPORT
By Col Collin Fay
Another month…and another
wing leader’s report. They
seem to come along so often!
March has started out well,
with the die-hard maintenance
crew wrapping up the extensive winter work on the TBM.
They have only a few more
nagging problems needing
completion prior to midApril. It now looks like our
first show will be at the
“Thunder and Lightning over
Arizona” open house / air
show at Davis-Monthan Air
Force Base in Tucson. This
should prove to be a special
show – celebrating Arizona’s
first 100 years of statehood –
with the USAF Thunderbirds
as the center piece (besides
ol’ 309, that is!) We’ll need
plenty of crew for this show,
so please sign up now. The
We now have 4 active RMWCAF Cadets . The newest
being Robert L. Tully a student at Central High
School. He has shown his tenacity and enthusiasm
by working on the TBM under the tutelage of "Cadet
Master" Col Bill Marvel.
Welcome Robert.
TBM will leave Grand Junction on Friday, April 13th, and
return on Monday, April 16th.
If you play your cards right,
you’ll get to fly in the TBM
piloted by our own Col. Matt
McNamara, famously recognized by Col. Bruce Verstraete at last year’s survivors’ party!
After the Arizona show, it
looks like we’ll have a lull in
the action for about 6 weeks.
We thought this might be a
good occasion for us to host a
local open house, showcasing
our aircraft and museum to
the Grand Junction and
western Colorado community. We’ll also use it as a
fundraising opportunity,
selling rides in the TBM
and Cub. But most importantly, we’ll use it as a
recruiting venue, hoping to
bring people in who are
interested in what we do
and want to help out.
Please plan to help us get
more interested people in
to our group! We haven’t
set a specific date yet, but
it will probably be on a
Saturday in early May.
As I mentioned last month,
we are going to be taking the
TBM to Midland for AIRSHO 2012, the Best Warbird
Show in America. It will be
held on October 13th & 14th,
and we hope to put together a
group from the Rocky Mountain Wing to attend. Please
let me know if you’d like to
attend, as we need to get hotel rooms booked early.
Thanks again to everyone in
the RMW for your help to
“keep ‘em flying.”
M ARCH - A PRIL 2012
HONORING AMERICAN MILITARY AVIATION THROUGH FLIGHT, EXHIBITION AND REMEMBRANCE
P AGE 5
RMWCAF STAFF OFFICERS
Wing Leader
Collin Fay
Executive Officer
Bruce Verstraete
Finance Officer
Don Coleman
Adjutant
Jerry McDonough
Operations Officer
Rob (Dunc) Duncan
Maintenance Off.
William (Bill) Marvel
Museum & Mess Sergeant
Dorothy Dutton
Safety Officer
Bob Thompson
Judge Advocate
Gerald Feather
Public Information Officers
Denis Godfrey
PX Officer
Georgia Thompson
Newsletter Editor
Tom Howe
TBM Aircraft Coordinator
Bob Thompson
Cub Aircraft Coordinator
Charlie Huff
Facilities Manager
Bruce Verstraete
Photo from the January/February issue of WARBIRD DIGEST #40
Recruiting Officer
Bob Caskey
Our very own Col Denis Godfrey took this photo at the 2011 NREE show
in Akron. Denis excels as our Public Information Officer gaining national
recognition for his never ending efforts
Other WWII Aircraft
Both Ours and Theirs
The Italian Camproni-Campini N1 made Italy the
second nation in the world to achieve jet powered flight (after Germany.) But the Italians sort
of cheated-using a piston engine to drive the
compressor fans for the turbojet. Close, but….
This Poster
dates to the
early British
nighttime
bombing
raids.
“The enemy sees
your light!
Darken!”
Blackouts
weren’t restricted to
Britain.
Morbid, eh?
RMW TBM APPEARS IN NATIONAL MAGAZINE
What Started it All?
So who started all
this “Torpedo Bomber” thing? The British first let a contract
for an aircraft specifically designed as a
Torpedo Bomber.
The AD Seaplane
Type 1000 was designed by the Admiralty’s
Air Department prior to
WWI. Seven were ordered but after the first
was delivered in 1916 it
was discovered the design
was not up to the task.
Only two were built and
the contract was cancelled.
The US’s first aircraft for
use as a Torpedo Bomber
was the Martin MB-1 first
delivered in 1918. The
Navy configured two for
Navy use as a Torpedo
Bomber and the Marines
had 8 Torpedo Bombers.
The AD-1 British Torpedo Bomber?
Marine TM-1 Note the folding wings.
M ARCH - A PRIL 2012
HONORING AMERICAN MILITARY AVIATION THROUGH FLIGHT, EXHIBITION AND REMEMBRANCE
The Avenger Gun Turret
Continued from page 1
gunner to let off the trigger in
the heat of battle as the gun
traverses past the tail location. Therefore the turret has
a fire interruption circuit.
This is primarily controlled
by a drum that hangs under
neath the turret. The drum
has cam profiles engaged by
followers connected to
switches. So as long as the
drum is timed correctly, a
gunner can hold down the
trigger and the interruption
circuit will cut out the electric trigger on the machine
gun before the barrel is pointed at the tail or wing.
The turret is armed with one,
caliber .50, Browning machine gun, M2, aircraft,
basic. One ammo can with
200 rounds was provided.
The trigger is mounted on the
joystick and a Mk.9 reflector
gunsight was used for aiming. When TBF’s first arrived
in the Pacific, the Japs got a
big surprise when attacking
astern. The twin .30’s on
SBD’s could only reach out
so far and the Zero’s knew
their effective range. But a
single “Ma Deuce” had a
greater range and punch than
the twin .30’s or the Zero’s
machine guns. WWII records
indicate 98 enemy aircraft shot
down by torpedo bomber
squadron’s. No doubt most of
those were from TBF turret
gunners. The gun turret was
used for air to air defense of
the aircraft. But it could also
be employed offensively with
great effect, such as strafing of
shipping or shore positions.
Sucks to be a turret gunner if
you had to bail out. Due to the
confines of the turret, the gunner cannot wear a parachute.
He does wear the harness, but
the chest parachute pack hangs
above the back door. For
ditching at least there is a
hatch on the port side of the
turret.
The turret in the RMW
Avenger is not operational,
however, we aspire to make it
so one day. Probably 50% of
the bits are in inventory but
we are in need of some major
components. The parts are out
there, somewhere, all that’s
needed is a CAF colonel to go
ferret them out!
Shown to the left is Col Dick Faucett and his grandson Jerod restoring the gun turret now installed on
“309”. Re-visit the Jan. 2011
Propwash to learn more about this
team.
P AGE 6
M ARCH - A PRIL 2012
HONORING AMERICAN MILITARY AVIATION THROUGH FLIGHT, EXHIBITION AND REMEMBRANCE
P AGE 7
AirSho 2012 is October 13 - 14
Midland and Odessa TX
will both be covered with
Colonels, airplane noise
and the smell of aviation
exhaust this October. Our
TBM ‘309’ and crew will
be there to assist in all
three categories.
If you’ve never been to an
AirSho, plan to go sometime. What a great collection of fine airplanes, fine
performers, and CAF
Colonels.
Walk and visit the static
displays, visit the vendors
and sister wing PX’s then
swing by the CAF Officer’s club for a small
libation.
This is when the CAF
really gets to strut it’s
stuff. The Headquarters
(HQ) staff outdoes themselves every year.
The CAF HQ Museum is
a must for any visitor and
the HQ PX has member
stuff you can’t find anywhere else.
There’s special member
registration available
ahead of time and special
parking available as well.
Your editor has attended
a number of past AirSho’s and never had a
dull moment at any.
A must for any CAF
Col’s Bucket List!
Winter Maintenance Continues - Eliminating Surprises
(Continued from page 3)
flare in the tubing was almost
non-existent and possibly had
been in that condition for 65
or so years since it was built!
Fortunately the line segment
is short, held in place by only
two clamps and can easily be
replaced with all new hardware which we have in stock.
It was yet another in the long
line of surprises this airplane
has revealed to us over the
years.
And not to be outdone, the
hydraulic system “sprung”
another surprise on us today,
March 8. There is a nice
little pool of hydraulic fluid
below the tail wheel and is
clearly coming from something in the wheel well. Next
Saturday is going to be a big
day…
The final few items in several
inspection checklists still
remain to be completed, but
at the rate we are moving the
airplane should be signed off
for flight about the same time
all the work is done. Valve
clearances have been set,
magneto timing checked, the
EGT problem solved, and the
engine test run. If only we
don’t have to change another
cylinder, the plane might be
able to fly again fairly soon.
But I am not betting on that.
This tube is
supposed to
have a very
distinct flare
on its end.
.