Science: Convertiplane Progress

Along the expanding sector in aircraft design known as VTOL (Vertical Takeoff and Landing), several U.S. companies have tried to meet military and civilian demands for a plane that can rise straight up, like a helicopter, then fly horizontally with the speed of conventional aircraft. Last week the first successful conversion in flight from helicopter to conventional aircraft was announced by the Defense Department. The pioneering hybrid: McDonnell Aircraft Corp.’s experimental XV1 convertiplane* (TIME, Feb. 15, 1954), designed for the Army and Air Force.

Half helicopter, half airplane, the stubby-winged XV1 made its second test flight one morning last week at an air field near St. Louis. Veteran Test Pilot John Noll warmed up the small Continental engine (less than 500 h.p.) behind his glass-enclosed “greenhouse”; two compressors began feeding air through tubes to small “pressure jets” at the tips of the three overhead rotor blades. As Noll opened the throttle, the fuel in the pods began burning in small, roaring jet gusts, expelling the hot air, spinning the rotor and lifting the aircraft off the ground. At 4,000 ft., ready for forward flight, Noll switched on the small pusher propeller, sited between the twin tail booms, and kept the rotor windmilling to supply extra lift. Coming in to land, he first slowed, then cut off the pusher, gave the rotors full power over the landing site, and set the XV1 gently to ground on its skids.

With a design speed of between 150 and 200 m.p.h., the McDonnell XVi is built to carry four passengers (or two casualties and a medic) plus the pilot. As an Army or Air Force jack-of-all-work, it may be used, after further development, to supplement slower, shorter-ranged conventional small helicopters for liaison, rescue and reconnaissance missions. Its enthusiasts see the XV1 as a major advance toward easier civilian air transportation in the future; by 1965 travelers may be able to board convertiplanes at skyscraper platforms within blocks of their homes or offices, speed off for a visit to a neighboring city without ever seeing an outlying airport.

* Bell is experimenting with convertiplanes that have huge rotorlike propellers which take the plane up, then tilt 90° forward for horizontal flight. Not to be confused with convertiplanes are the Navy’s Convair XFV1 and Lockheed XFV-1, which take off and land vertically on their tails, merely nose over for level flight.