Aachen FVA 11 Eifel
The design goal for the FVA-11 was for the "ideal aircraft” with good glide ratio and low landing speed. Primarily the demand for the cruising speed of 80 kph and an optimal glide efficiency.
The aim was for reasonable rates of descent even at 50 kph and that the landing speed, as a measure of security against crash landings, came as close as possible in 40 kph.
The most difficult demands were the glide ratio and cruise speed. To fulfill this , all residual resistance had to be kept as small as possible and the use of thin airfoils was required. This brought his hand back significant construction difficulties. It was found that the demands for sinking speed and glide could be met with a wingspan of 18 m. However, with the wing load of 21 kg/m² was not able to fall below a minimum speed of 56 kph.
It was necessary for a landing aid be used not only for a sufficient increase in lift, but also with minimal additional drag. The best solution at the time appeared to be Fowler flaps 30% depth in the infield between fuselage and aileron, while in the outer wing, the ailerons simultaneously in a new zero position.
The elaborate fittings for guiding the auxiliary wings were mounted on the underside of the wing. In order not to get too much drag with separate ailerons, the ailerons were designed so that they did not make any further downward deflection, but comes up to full swings.
In order to obtain sufficient documentation for performance and stability calculations, it was decided to examine the proposed flaps in the Aachen wind tunnel. The model was carried out in our workshop. The flap arrangement was such that the flap was able to be adjusted from 0 to 40° in 5° increments. For all these flap positions comparisons were made. The results confirmed the design. The landing speed of 42 kph was reached and the acceptable rates of descent at 50 kph were achieved. The lowest Sink rate rose from 0.6 to 0.7 m/sec.
With the construction of the machine started at the end of February 1938, on the first day of the Rhön competition it was flown in Aachen. The test-flight happened by aerotow.
The FVA flew the "Eifel" to the Rhön competition, but the aircraft was flown there but not much. This was mainly because the FVA-11 was not yet ready for competition, still brand new and with its complicated and untried wings. In addition, at this competition there were substantial highs, and to go with an untried wings in cumulonimbus clouds, appeared not appropriate. The accidents that existed during this competition justified this view.
Contrary to the views expressed in the Annual Report 1938/39 hope some planned changes to the FVA-11 were not completed by August 1939 and the machine was destroyed during World War 2.