VTOL for flaps, retractable slats. From wikipedia: The Buttercup was considered as the basis for a four place certified production model by Fairchild Aircraft. Fairchild executives were impressed with the aircraft that chance landed at their factory airport in Hagerstown, Maryland. Wittman sold production rights, but Fairchild did not pursue the effort due to wartime production obligations.[4]Experimental Aircraft Association member Earl Luce developed a replica Buttercup design which first flew April 14, 2002.[5] His representation of the Buttercup design is available as a set of plans for home builders.[6]. My perosnal favorite airplane of all time, and often an overlooked one. Predecessor to the famous W-10 Tailwind. Featured retractsble slats that chsnged the camber of the wing, increasing the lift and lowering the stall speed to 37mph . Also, in true wittman fashion, is capable of cruising at 140 mph. All on an O-200 continental. Find me a Cessna 150 that can top THAT