Vertical Takeoff and Landing Vehicles
Commonly referred to as Vertical/Short Takeoff and Landing (V/STOL) aircraft, V/STOL planes arose from aviators' desire to combine the takeoff and landing abilities of helicopters with the fast, long-range flight abilities of airplanes. V/STOL technology has been of particular interest to the military, since it both enhances the ability of aircraft to operate from platforms other than aircraft carriers, as well as to operate in remote areas where airports with adequate runways are not available.
V/STOL development began shortly after the end of World War II, and after a number of failures (an inevitable part of experimentation with new technology) the first V/STOL prototype, the Hawker P1127, made its initial test flights in 1960. This prototype eventually led to production of the most successful V/STOL aircraft yet produced the AV-8 Harrier "Jump jet."
Although proven in battle, the Harrier has all the drawbacks of V/STOL aircraft. The dual requirements of helicopter-like and plane-like performance lead to extremely heavy aircraft, and the Harrier can neither carry a large payload nor fly supersonically. To alleviate this, experiments are underway regarding aircraft that can land vertically but take off on a significantly shortened runway. The relaxation of the takeoff requirements results in a greatly increased payload, while still not requiring a full runway or full-size aircraft carrier for safe operations.
A different type of V/STOL aircraft is the helicopter-like V-22 Osprey, which employs two swiveling tilt-rotors that allow it to take off and land very much like a helicopter, while flying with performance comparable to a turboprop airplane. Although the Osprey is considerably slower than the Harrier, mangaing only 300 knots in cruise mode, it can carry a much larger payload and answer some of the objections about the Harrier's limited transport ability. An outgrowth of the Bell XV-15 tiltrotor aircraft program, the Osprey was developed in the 1980s and made its first flight in 1989, after which funding for the program was cancelled. A renewal occurred in 1992, however, and a lighter, faster version of the Osprey was delivered by Bell Boeing in March of 1997.
Future developments in V/STOL technology may fuse the two concepts above. Planes like the Harrier employ jet engines that can provide vertical as well as horizontal thrust, and in general they look more like airplanes than helicopters. The Osprey, on the other hand, looks more like a mutant helicopter, employing tiltrotors than can propel it forward more efficiently than a true helicopter's. Investigations are proceeding that may combine these concepts, employing a tiltrotor that is used for hovering takeoff and landings, and which then literally stops and turns into a wing for fixed-wing flight. The technical difficulties with such a craft are manifest, and remain under development.
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