it was planned to power the rg.40 with a ava 4a-02, an air-cooled, flat four, two stroke engine, mounted in the nose with cylinder-heads projecting for cooling, but the earliest flights were made with a smaller bore version, the ava 4a-00. the week-end's rectangular cross-section fuselage had a wooden structure and was ply covered. the forward view from the cabin was through a long, one-piece transparency and the only sideways obstructions were the two pairs of vertical members that joined fuselage and wing. cabin entry was via two large doors.