FVA 10a - Theodor Bienen
After the good successes with the FVA-9 “Blue Mouse II”, Benno Sann, Walter Trapp, Artur Getto and August Schulte began designing the FVA-10 as early as the following year in 1935. In a consistent further development of the FVA-9, which was designed more as a training glider due to its strutted high-wing construction, the FVA-10 was to become a high-performance glider corresponding to the state of development at that time. Thus, similar to the FVA-9, the development of the FVA-10 was initially based on very extensive wind tunnel tests on a model in order to obtain an optimum fuselage-wing transition.
The design was based on the assumption that the aircraft could be unloaded and fully assembled by three people without assistance in five minutes.
In accordance with the state of development at that time, a cantilevered articulated wing was designed and the center wing arrangement was selected. Assembly was very simple, each wing being mounted to the canopy separately. Only three bolts were screwed in from the outside on each side, while ailerons and airbrakes connected automatically (!).
The wing had a trapezoidal outline and in its course from the inside to the outside the profiles Jukowski 433, Göttingen 532 and USA M 3. The construction of the wings was as usual single spar with a torsionally stiff wing leading edge. The spar had an I cross-section, spar chords and all other locally stressed components were made of heat-treated wood. The ailerons of the three-part wing went through the entire outer wing and were mounted in self-aligning ball bearings. The airbrakes were located only on the upper wing surface within the ailerons.
The fuselage shape was chosen in such a way that at the best cruising speed the influence of the fuselage on the lift distribution over the span was minimized. The forward fuselage section was built as an open, double-walled shell, with the pilot’s seat designed so that the pilot rested comfortably everywhere from the back of the knees to the back of the neck. The collapsed canopy was of removable design, but in tubular steel and completely covered with cellophane.
The tail boom was a torsionally and flexurally rigid tube without ribs but with light stiffening rings. Rudder and elevator were damped. The elevator was attached with three bolts accessible from the outside.
Since the fuselage was extremely narrow for aerodynamic reasons, it was decided to incorporate an unconventional handwheel control system into the glider. The entire control system was ball-bearing, and elevator actuation was by pushrods and cables. The rudder pedals were adjustable without the need to change rope lengths.
(This description was compiled from a keyword publication in “Flugsport” 1937. No.19).
It is already clear from the description of the FVA-10 that this design contained some sensational details for the time, which are still quite contemporary today. The FVA-10a was completed in late summer 1936 and christened “Theodor Bienen”. The first flight took place at Merzbrück still without a canopy.
Immediately after the first test flights, which were carried out by Felix Kracht, the first alpine glider tests were carried out in Prien (Chiemsee). The canopy was also completed there. The first longer flights in the foothills of the Alps showed that the flight performance and flight characteristics were excellent.