the engines all had problems with mixture due to changes in engine speed or load, which led to rough engine operation. In August, while Bede was demonstrating the BD-5 (N501BD) to the FAA in order to receive permission to fly at Oshkosh, the engine seized. On its deadstick landing, the aircraft overran the runway, buckling the nose gear. Incorrect mixture was identified as the cause of a second wreck of N501BD, in September 1972, when the mixture control broke and Berven had to execute another forced landing. This landing resulted in damage to all the gear and the fuselage as well. Since N502BD would be ready in two months, they decided not to repair N501BD, and it ended testing after about 30 hours of flight time. N502BD N502BD ran into problems of its own. Early models used a variable speed belt drive system to transfer power from the engine to the propeller shaft. This was removed from N502BD and it suddenly began exhibiting a serious vibration problem during taxi tests. Experts were called in, and a freewheel clutch and additional bearings added to correct the problem, but it was not until March 26, 1973, that N502BD flew. From then on the test program seemed to go more smoothly, although this aircraft also suffered two dead stick landings, one from a pinched fuel line occurred while the plane was being observed by the Popular Science author, and another due to metal in a new engine's cylinder. By the time the test program neared its conclusion, the aircraft had undergone major changes. One victim of the program was the shorter "A" wing, which calculations showed would only improve performance at speeds very close to Vmax (the highest available speed). Flight testing also showed the stall speed with the smaller wing was decidedly high. Split flaps and spoilers had also disappeared. The canopy and cockpit dimensions had changed, the aircraft had new landing gear systems, and the tail was completely new. Estimated top speed was also reduced 10%. The biggest change, however, was the engine. The original plans to use a 40 hp model proved to be decidedly underpowered, although they were still offered for a time. It was the need for more power that would fit into the very small engine bay that demanded the use of a high-revving two-stroke engine, and few examples of such a design in the desired power