Bucker Bü-131 - The Bücker Pages

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Via internet, you might have got the news a German workshop in partnership with the
distributor of the Polish built T-131 aircraft, are planning to construct the Bü-131-B
airplane.
We believe, this idea is wrong, as it means a setback in the Jungmann development
process.
Here are the reasons:
-The Bü-131-B aircraft was a modification made in 1936 to the Bü-131-A type, wich
flew for the first time in April 1934.
-The Bü-131-A had been designed under the limitations of the "Versalles Treaty";
Germany was not to be allowed to produce engines of more than 80 hp; so, the engine
used was the HIRTH HM 60R/2 of 80 hp. As a consequence, the airplane had to be
designed as light as possible and the result was a couple pilots, biplane with an empty
weight of 350 kg. and MTOW of 630 kg.
At a later stage, when a higher power engine could be used, the Bü-131-B was
produced; it was powered by the HIRTH AM 504 A2 giving 105 HP. As a consequence,
the airplane empty weight became 380Kg. and a MTOW of 670Kg. The empty weight
difference (30 Kg.) was the result of the increased engine weight (15 Kg.) and the
weight resulting from reinforcing the engine bearers and other elements, because of the
weight and power change of the engine. The power increase allowed the BÜ-131-B to
climb to 3.000 ft. in 5 minutes and 20 sec., while the Bü-131-A needed 7 minutes and
40 sec. to climb to that same altitude. Also, the speed increased from 175 km/h.(model
Bü-131-A), to 185 km/h (Bü-131-B model).
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In 1937, though, these desing presented some difficulties and other changes had to be
made to the Bü-131-B, Bü-131-B2 and later on to the Bü-131-B3 model.
The Bü-131-B type, was built in Checoeslovaquia as TATRA T-131 (35 units), and in
Switzerland as DORNIER Do/BU-131-B (84 units).
The short life of model Bü-131-A and Bü-131-B, was as a result of the poor
performance caused, in the Bü-131-A, by the low power, and in the case of the Bü-131B, for using the same fuselage as in the model Bü-131-A (P/N8-131-00), tail (P/N 8131-300) and quite a number of other elements.
In 1938, due to the poor performance of the Bü-131-B, Bü-131-B2 and Bü-131-B3, a
new aircraft design was made in Germany: the Bü-131-D, and later on, the Bü-131-D2.
The Bü-131-D2 model ,was the one built in Spain (200 units).The Bü-131-A and Bü131-B models witch still were in service when the CASA 1131-E production was
started, were converted to the new model CASA 11311-E (E.3B) together with the Bü131-D2. All Spanish Air Force Bücker’s were converted to the CASA 1131-E
(E3B) model.
The main differences of the Bü-131-B model in relation to the models witch followed
are:
1.-Fuselage.
2.-Tail.
3.-Ailerons and Wings.
4.-Undercarriage.
5.-Flight controls.
6.-Equipment.
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1) Fuselage
Bü-131-B fuselage
A) Station 0: The front of the fuselage had been studied for an engine with a power of
80 hp, a weight of 97 kg and a length of 878 mm. The engine of model Bü-131-B had
105 hp, weighted 112 kg and was 993 mm long, so, in order to keep the same centre
of gravity, the airplane had to be shortened.(40mm.).
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Station 0
B) The attachment fittings of the security harness of the front seat were attached to the
rear wing spar, close to the main fuselage tubes. This arrangement, causes the fittings to
interfered with the cables of the flight controls creating a potential unsafe situation (see
part 6, Equipment)
Front seat harness attachment points.
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C) The rudder turning point was a stiff hinge, while the models wich followed used
floating ballbearings, wich resulted in a good improvement.
D) The rear end fuselage heel a was concave sheet metal piece without room for the
trailing bar on the ground. It was quite hard to move the airplane around in the ground.
E) There is no arrangement for adding weight in order to correct the airplane centre of
gravity.
Lower turning point hinge of the rudder and bolt and heel.
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2) Tail
Bü-131-B tail
The tail had the following anomalies:
A) The turning of the rudder is done on rigid hinges, some attached to the fuselage and
some to the drift; resulting more rigid than in subsequent models.
B) The bottom part of the rudder is straight and very near the floor, so it may touch the
floor in wide angle landing.
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The bottom part of the rudder and rigid hinges.
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C) The elevators have no manholes for the assembly and control of the turning points,
so it is impossible to control the turning.
Elevators impossible inspections.
Bü-131-B tail
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3) Wings and Aleirons
Bü-131-B wing.
A) The main spars of the wings are made with only two pieces of wood whereas in
subsequent models they are made with four which prevents them from twisting.
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Spars of the wings are made with only two pieces.
B) The hinges of the ailerons in the ribs 6,8 and 10 are rigid (female).
Ailerons in the ribs.
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C) The hinges of the ailerons are rigid (male). In subsequent models, they are
oscillating ball bearings to absorb the distortions that may be produced by the
aileron (wood).
The hinges of the ailerons are rigid.
The hinges rigid parts.
D) The leading edge in each aileron is 85mm shorter than in subsequent models.
This lowers the compensation of ailerons functioning and efficiency.
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The control pulley of the tail wheel is made of celotex (pressed fabric); in subsequent
models it is made of bronze for longer duration and safety.
The leading edge in each aileron is 85mm shorter than next versions.
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4) Undercarriage
The control pulley of the tail wheel is made plastic material.
The control pulley of the tail wheel is made of celotex (pressed fabric); in
subsequent models it is made of bronze for longer duration and safety.
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5) Controls
A) The control of the elevators is done with cables; and in subsequent models it is done
with a steel rod since it is safer.
The control of the elevators is done with cable.
B) The rear bellcrank hinges of the elevators turn on 6mm screws. In subsequent
models they turn on an 8mm hinge of oscillating ball bearings, so safety increases.
The rear bellcrank hinges turn on screws.
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C) The control cables of the rudder are not adjustable in rear pedals; in subsequent
models it is possible to adjust them.
The control cables of the rudder are not adjustable.
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D) The guide of the left cable of the rudder moves on celotex; in subsequent models it is
done on a pulley, thus avoiding wear.
The guide of the left cable of the rudder moves on fiber.
A) E) Sticks are straight; in subsequent models they are curved to facilitate the
pilot’s flight control.
Sticks are straight.
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6) Equipment
A) The windshields are curved; in subsequent models they are flat to avoid
distortions.
B) The co-pilot front seat doors are rectangular; in subsequent models they are
trapezoid to offer the crew more protection.
The windshields are curved and front seat doors are rectangular.
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C) The cables of the front seat belts are attached to the fuselage to avoid interfering
with controls; in subsequent models they are attached to the middle of the main rear
spar under the pilot’s front seat, since in this position they do not interfere with
flight controls.
Cables of the front seat belts.
.-oOo-.
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ANNEXES
I.- Bucker Bü-131 “Jungmann” evolution.
AIRPLANE BUCKER JUNGMAN EVOLUTION
First : Bü-131-A
Second: Bü-131-B (1)
Third:Bü-131-B2
Fourth : Bü-131-B3
Fifth :Bü-131-D
Sixth:Bü-131-D2
Seventh: CASA 1131-E (2)
The model that the German garage is attempting to make is model Bü-131-B (1) and
the model that BUCKER-PRADO is reconstructing, with original documents, is
CASA 1131-E (2), which has been considered one of the best Bucker Jungmann
planes by Carl Klemens Bücker himself.
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II.- Explanation of the best Jungmann airplanes (16-8-1980)
Parece estar absolutamente de moda criticar el 1131 español como inferior, pero la
crítica nunca parece venir de personas realmente conocedoras de estos aviones.
Teníamos un Jungmann español, suizo, y checo que estaban lado a lado el año pasado,
y eran mirados por un señor quien probablemente tiene más tiempo y experiencia
alrededor de los 131 que cualquier otra persona en los E.E.U.U. y quien posee un
Jungmann checo que puede ser el mejor del país. Su opinión era que los aeroplanos
españoles eran de construcción mucho más moderna, muy agradable, deseable, y
tienen controles de rodamiento de bolas que los aeroplanos suizos carecen. También,
conseguimos una nota del historiador y escritor de la aviación John Underwood, que
estaba en la comunicación con Carl Bücker durante muchos años. Él recuerda a Herr
Bücker diciendo que los aeroplanos de Chechoslovakia y España fueron construidos
mejor que en Alemania.
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