Aachen FVA 20
With the decision to build a standard class aircraft, the design was already outlined in broad terms: 15m span, no lift and flaps and minimum body height 0.8m.
For the wings , the rectangular trapezoidal shape was chosen , which offers significant manufacturing advantages. The minimum surface load of 26,8kg/m² promises satisfactory flight performance even in the European weather conditions. T-tail , retractable landing gear and the proven Schempp-Hirth airbrakes were features that were maintained from the beginning.
The hull construction was begun in 1967, but the half-finished hull was for a long time in a corner of the workshop without anything happening.
Construction was half-sandwich type. Balsa wood was used as a support material for a fiberglass shell. The vertical tail fin and tailplane used the same construction, as a full-sandwich in a negative mold.
The wings were originally similar to the hull, produced in positive construction. However, it turned out that with this construction, the required high profile accuracy was difficult to achieve. Aachen changed to the negative construction. The spar is designed as a box spar, and for the spar caps roving cloth was used in the form of narrow bands.
The FVA-20 was the first fiber reinforced plastic glider built by the FVA. The FVA initially lacked the designers and builders on experience with the new material.The FVA was not discouraged by setbacks and consistently worked on the project.Among many other designers especially Uwe Solies came forward, who was project manager of the FVA-20 many years and spent many a night in the factory before the drawing board.
Since 1973, every year you could read again in the annual report that "we expect the first flight over the next racing season." In addition to a coarse underestimate the amount of work especially the "Details".In contrast to previous FVA-aircraft designs, made with all available work force, in the seventies with only with one project: the maintenance of the aircraft fleet, design and construction of several trailer for the newly acquired gliders took at times most of the work capacity to complete.
When finally construction began on the wings, it was discovered that the negative forms already standing in the workshop for several years set themselves so that the required surface finish and profile accuracy could not be reached. The shapes were restored to the necessary condition in winter 1975/76 which proved to be very lengthy. In March 1976, they could finally begin on the upper and lower shells of both surfaces, laminated in the form of mass inserts.
In these shells the "guts" were inserted and then the respective upper and lower shells joined together. The profile accuracy in the wing leading edge was work in the following winter.
In 1978/79 the work was continued intensively. But again there were problems in the so-called details, which caused further delays. For example, the incorporation of control organs, control levers and the actuation of the retractable undercarriage saw some problems.
During the general development some improvements were also incorporated into the design of the FVA-20. For example, the control stick and the mating of the wings is done by Hänle fashion. The surfaces were drawn together by means of a lever assembly.
on 27 November 1979 the provisional airworthiness certification by the Luftfahrt-Bundesamt was picked up by Joachim Ewald (Cassius), who was selected for the first flight. On 28 November 1979 at 10:20 Ewald lifted the FVA-20 behind towplane still unpainted. Joachim Ewald unlatched from 2200m.
The FVA-20 made a total of three flights that day and was then immediately returned to the workshop where many details were still to finished and the aircraft painted. flight testing finished with a final flight in March 1980.