Tilting Plus Swiveling Makes Agile Aircraft

Whatever weapons the Air Force finally gets for big wars of the future--manned supersonic bombers, or more potent missiles, or a mix of both--there is little argument about what is needed for the small, brushfire battles of the present. Army, Air Force, Navy and Marine Corps all agree that they need fighter planes and transports husky enough to handle modern armament, yet agile enough to take off and land on back-country roads or small jungle clearings.

The problems that must be solved are already encouraging fanciful flights of aerodynamicists' imaginations. The suggested solutions are many and bizarre. Some of the more interesting:

> TILT WING: Rolled out last week by Ling-Tempco-Vought, Inc. of Dallas, the XC-142A transport has four turbo-prop engines and a wing that can be tilted for takeoff so that its four 15.6-ft. propellers point upward. When they all are pulling together, the props should generate enough direct lift to raise the plane vertically. When safely above obstacles, the pilot will gradually tilt the wing into normal flying position. The plane has yet to be flown, but its designers admit that it is no speedster. It will cruise at less than 300 m.p.h., and its operating radius with full load is only about 230 miles. These limits are the penalties it pays for its vertical lifting power.

> TILT ENGINES: Other aircraft designers prefer to keep their wings fixed and to swivel only the engine or the engine exhaust. The Curtis-Wright X-19 has four tillable engines on the tips of two stubby wings. The Bell X-22A has four tiltable propellers in circular ducts. Neither plane has yet completed successful tests, but two years ago the British were already flying the Hawker Siddeley P-1127, which has a single jet engine with 13,500 lbs. of thrust. During takeoff, the engine's exhaust gases are diverted downward, exerting enough thrust to lift the airplane off the ground. At cruise altitude, the exhaust is switched to the rear and the plane flies in normal jet-plane style. The P-1127 has done everything claimed for it, but its payload is small, and it is too slow to be of much value as a fighter. Hawker Siddeley is building a bigger model with a more powerful vectored thrust engine that it expects to be supersonic and also able to take off from British lanes.

> LIFT ENGINES: In yet another approach to the problem, France's Dassault Mirage III-V will pack eight small Rolls-Royce jet engines thrusting downward. When well in the air, a larger jet will take over and push the plane forward at supersonic speed. Its designers admit that the vertical engines will be dead cargo most of the time, but they think vertical engines will have less effect on performance than dual-purpose engines that are too powerful for efficient horizontal flight. A German V/STOL, the Boelkow, Heinkel and Messerschmitt VJ-101C, varies the French formula slightly by having two main engines that are tiltable and supplementing their thrust with two vertical-lift engines. The VJ-101C has made many vertical takeoffs with successful transition to horizontal flight.

> LIFT FAN: Perhaps the most imaginative design of all is the XV-5A lift fan built by Ryan Aeronautical Co. and General Electric. At first glance, it looks like an ordinary jet fighter with two engines, but set into the stubby wings are what seem to be large manhole covers. When opened, each cover exposes a fan 5 ft. in diameter. When valves close off the tailpipe of the jet engines, racing exhaust gases hit the tips of the fan blades and spin them at high speed. Twin blasts of air are forced downward, and their powerful thrust lifts the airplane off the ground. Transition to horizontal flight is made by gradually opening the normal tailpipe and covering the wing fans. So far the XV-5A has been tested only in conventional flight. If the XV-5A succeeds in taking off vertically and making the transition to horizontal flight, it will be the only speedy V/STOL that does not carry more engine power than it needs to fly on the level.

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