Bede remained convinced of the validity of the kit built market, and re-formed his company as Bede Aircraft. Here he started the design of an even simpler-to-build aircraft, the Bede BD-4.
The BD-4 used more conventional construction techniques, based on a simple high-wing design, and had few curved surfaces. Most of the fuselage was flat aluminum sheeting, the only major components with compound curves being the engine cowling and landing gear spats which were made of fiberglass. One real innovation was the "panel-rib" construction which reduced building time of the wing. Basically the wing was constructed in sections consisting of a rib whose upper edge was "extended" horizontally to become one section of the wing surface as well. The wing was built up by sliding these sections together over the circular spar and fastening them together where they met.
Like the BD-1, the BD-4 offered excellent performance; using the same 108 hp Lycoming O-235 as the AA-1 it could reach 130 knots. It could also be equipped with engines up to 220 hp, which was to top out at 190 knots (350 km/h) with a 170 kt (315 km/h) low-power cruise. The aircraft could be completed with either tricycle or tail-dragger configurations.
The BD-4 first appeared in 1968 and became a "hit". Thousands of plans were sold, hundreds were built, and many are still flying today. Early performance estimates were overstated; even with the large engines speeds were more typically 130-150 kt (240–280 km/h). The aircraft has proven to be very strong, and has an excellent safety record.
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