 Tiltrotors generally have better hover efficiency than tiltwings, but less than helicopters.In 1968, Westland Aircraft displayed their own designs—a small experimental craft (We 01C) and a 68-seater transport We 028—at the SBAC Farnborough Airshow.In 1972, with funding from NASA and the U.S. Army, Bell Helicopter Textron started development of the XV-15, a twin-engine tiltrotor research aircraft.