We believe, this idea is wrong, as it means a setback in the Jungmann development process.

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2 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 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 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). 2 / 21

3 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-131- B, for using the same fuselage as in the model Bü-131-A (P/N ), tail (P/N ) 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 Bü- 131-B models witch still were in service when the CASA 1131-E production was started, were converted to the new model CASA E (E.3B) together with the Bü- 131-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. 3 / 21

4 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.). 4 / 21

5 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. 5 / 21

6 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. 6 / 21

7 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. 7 / 21

8 8 / 21 The bottom part of the rudder and rigid hinges.

9 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 9 / 21

10 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. 10 / 21

11 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. 11 / 21

12 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. 12 / 21

13 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. 13 / 21

14 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. 14 / 21

15 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. 15 / 21

16 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. 16 / 21

17 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. 17 / 21

18 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. 18 / 21

19 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-. 19 / 21

20 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. 20 / 21

21 II.- Explanation of the best Jungmann airplanes ( ) 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. 21 / 21