V-22 Osprey

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The V-22 Osprey is a joint service, multi-mission aircraft with vertical take-off and landing (VTOL) capability. It is designed to perform VTOL missions like a conventional helicopter while also having the long-range cruise abilities of a twin turboprop aircraft.

The Osprey is the world's first production tiltrotor aircraft with a 38 ft (12 m) rotor, engine, and transmission nacelle mounted on each wing tip. It typically operates as a helicopter with its nacelles vertical (rotors horizontal) for takeoff and landing. Once airborne, the nacelles rotate forward 90 degrees in as little as 12 seconds for horizontal flight, converting the V-22 to a high-speed, fuel-efficient turboprop airplane. STOL, rolling-takeoff and landing capability is achieved by having the nacelles tilted forward up to 45 degrees. For compact storage aboard a ship, the wing rotates (about the z-axis), and the proprotors fold in a sequence that takes between 90 and 120 seconds.

The United States Marine Corps is the lead service in the development of the V-22 Osprey. The Marine Corps version, the MV-22B, will be an assault transport for troops, equipment and supplies, and will be capable of operating from ships or from expeditionary airfields ashore. The planned, but as yet unfunded, US Navy V-22 will provide combat search and rescue, delivery and retrieval of special warfare teams along with fleet logistic support transport. The CV-22 operated by the United States Special Operations Command (USSOCOM) will conduct long-range special operations missions, combat rescue, among other special missions. The V-22 Osprey will replace the Marine Corps CH-46E and CH-53D as well as several types of the Special Operations Command MH-53 Pave Low and possibly some C-130 Hercules series aircraft.

The Osprey was developed and is built jointly by Bell Helicopter - Textron, who manufacture and integrate the wing, nacelles, rotors, drive system, tail surfaces, and aft ramp, as well as integrating the Rolls-Royce engines; and The Boeing Company, who manufacture and integrate the fuselage, cockpit, avionics, and flight controls. Portions are manufactured in Philadelphia, Pennsylvania, and Amarillo, Texas. Final assembly and delivery occurs in Amarillo, Texas. The joint development team is known as Bell-Boeing.

Development

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The Osprey's development process has been long and controversial. The first flight occurred in March 1989. Since then, however, there have been four significant failures during testing - a crash in 1991, a second in 1992 that killed seven, a third in April 2000 that killed 19, and a fourth in December 2000 that killed four. It is claimed that problems identified in all of these mishaps have been addressed by the V-22 program office and advocates of the program are optimistic that the aircraft is mature enough for fleet operations. Critics state that the aircraft will never be mature enough for reasons of pure physics — the V-22 cannot be fixed because of its flawed side-by-side rotor design, although the tandem rotor CH-46 and CH-47 helicopters have been operational for over 30 years.

The cause of the April 2000 crash was investigated, and was officially determined to be due to a rate of descent of over 2000 feet per minute (600 m/min) of the aircraft while at slow horizontal speeds of around 30 knots (56 km/h). Any rotorcraft descending too fast relative to its horizontal speed can induce an aerodynamic phenomenon whereby the air flow below the rotors recirculates outward, up, and back through the rotors, effectively producing a bubble-like air flow pattern around the entire craft that results in a wing stall-like effect called vortex ring state (VRS). Subsequent testing has shown that the Osprey, and the tiltrotor in general, is less susceptible to VRS, that the conditions are more easily recognized by and presented to the pilots, that recovery from VRS requires a more natural action by the pilot than for helicopters, and that the altitude loss is significantly less than for helicopters. Recognition of and recovery from VRS is also easily trainable for new pilots.

At the time of the mishap, the Osprey's flight operations rules restricted the Osprey to an 800 feet per minute (240 m/min) descent at lower than 40 knots (74 km/h) airspeed (restrictions typical of helicopters, as well); the crew of the mishap aircraft exceeded this operating restriction threefold. Another factor that may trigger VRS is helicopters operating in close proximity, a possible scenario for all military rotary wing aircraft. As a result of testing, the Osprey will have a descent envelope as larger or larger than most helicopters, further enhancing its ability to enter and depart hostile landing zones quickly and safely.

Critics, however, believe the current solution is inadequate: Osprey has currently dealt with the problem by adding a warning light and simultaneous voice that says "sink rate" when the Osprey is close to VRS. While this addition is important for the craft's safety, some question whether this will limit effectiveness in combat zones, where it is supposed to operate, that require fast and sudden maneuvers.

The Osprey completed its final operational evaluation (OPEVAL) in June 2005. The OPEVAL was extremely successful; events included long range deployments, high altitude, desert and shipboard operations.

On September 28, 2005, the Pentagon formally approved full-rate production for the Osprey. The current plan is to boost production from 11 a year to 24 to 48 a year by 2012. Planned production quantities include 360 for the Marine Corps, 48 for the Navy, 50 for the Air Force. The US Army, originally the lead service for the then-named JVX program, is also a candidate for possible applications.

The Osprey will enter operational service with the Marine Corps in 2007.