petak, 26. ožujka 2010.

V-22 Osprey

The Bell-Boeing V-22 Osprey is a multi-mission, military, tiltrotor aircraft with both a vertical takeoff and landing (VTOL) and short takeoff and landing (STOL) capability. It is designed to combine the functionality of a conventional helicopter with the long-range, high-speed cruise performance of a turboprop aircraft. The V-22 was developed and is manufactured jointly by Bell Helicopter, and Boeing Rotorcraft Systems. It is operated by the United States Marine Corps and Air Force.
The first of six MV-22 prototypes first flew on 19 March 1989 in the helicopter mode and on 14 September 1989 as a fixed-wing plane. The third and fourth prototypes successfully completed the Osprey's first Sea Trials on the USS Wasp in December 1990. However, the fourth and fifth prototypes crashed in 1990-91. Flight tests were resumed in August 1993 after changes were incorporated in the prototypes. From October 1992 until April 1993, Bell and Boeing redesigned the V-22 to reduce empty weight, simplify manufacture and reduce production costs. This redesigned version became the B-model.
In 2000, there were two further fatal crashes, killing a total of 19 Marines, and the production was again halted while the cause of these crashes was investigated and various parts were redesigned
The V-22's development process has been long and controversial. When the development budget, first projected at $2.5 billion in 1986, increased to $30 billion in 1988, then-Defense Secretary Dick Cheney tried to zero out its funding. He was eventually overruled by Congress. As of 2008, $27 billion have been spent on the Osprey program and another $27.2 billion will be required before the program is completed.
The aircraft is incapable of autorotation, and is therefore unable to land safely in helicopter mode if both engines fail. A director of the Pentagon's testing office in 2005 said that if the Osprey loses power while flying like a helicopter below 1,600 feet (490 m), emergency landings "are not likely to be survivable". But Captain Justin (Moon) McKinney, a V-22 pilot, says that this will not be a problem, "We can turn it into a plane and glide it down, just like a C-130". A complete loss of power would require the failure of both engines, as a drive shaft connects the nacelles through the wing; one engine can power both proprotors.[21] While vortex ring state (VRS) contributed to a deadly V-22 accident, the aircraft is less susceptible to the condition than conventional helicopters and recovers more quickly. The Marines now train new pilots in the recognition of and recovery from VRS and have instituted operational envelope limits and instrumentation to help pilots avoid VRS conditions.

The Osprey is the world's first production tiltrotor aircraft, with one three-bladed proprotor, turboprop engine, and transmission nacelle mounted on each wingtip. It is classified as a powered lift aircraft by the Federal Aviation Administration. For takeoff and landing, it typically operates as a helicopter with the nacelles vertical (rotors horizontal). Once airborne, the nacelles rotate forward 90° in as little as 12 seconds for horizontal flight, converting the V-22 to a more fuel-efficient, higher-speed turboprop airplane. STOL rolling-takeoff and landing capability is achieved by having the nacelles tilted forward up to 45°. For compact storage and transport, the V-22's wing rotates to align, front-to-back, with the fuselage. The proprotors can also fold in a sequence taking 90 seconds.

Boeing has admitted that the V-22 design loses 10% of its vertical lift over a Tiltwing design when operating in helicopter mode because of airflow resistance due to the wings, but that the Tiltrotor design has better short takeoff and landing performance.

Most Osprey missions will use fixed wing flight 75 percent or more of the time, reducing wear and tear on the aircraft and reducing operational costs. This fixed wing flight is higher than typical helicopter missions allowing longer range line-of-sight communications and so improved command and control.

The V-22 is equipped with a glass cockpit, which incorporates four Multi-function displays (MFDs) and one shared Central Display Unit (CDU), allowing the pilots to display a variety of images including: digimaps centered or decentered on current position, FLIRimagery, primary flight instruments, navigation (TACAN, VOR, ILS, GPS, INS), and system status. The flight director panel of the Cockpit Management System (CMS) allows for fully-coupled (aka: autopilot) functions which will take the aircraft from forward flight into a 50-foot hover with no pilot interaction other than programming the system.

The V-22 is a fly-by-wire aircraft with triple-redundant flight control systems. With the nacelles pointing straight up in conversion mode at 90° the flight computers command the aircraft to fly like a helicopter, with cyclic forces being applied to a conventional swashplate at the rotor hub. With the nacelles in airplane mode (0°) the flaperons, rudder, and elevator fly the aircraft like an airplane. This is a gradual transition which occurs over the entire 96° range of the nacelles. The lower the nacelles, the greater effect of the airplane-mode control surfaces.

U.S. Naval Air Systems Command is working on upgrades to increase the maximum speed from 250 knots to 270 knots, increase helicopter mode altitude limit from 10,000 feet to 12,000 or 14,000 feet, and increase lift performance.

Specifications (MV-22B)

General characteristics

  • Crew: Four (pilot, copilot and two flight engineers)
  • Capacity: 24 troops (seated), 32 troops (floor loaded) or up to 15,000 lb (6,800 kg) of cargo (dual hook)
  • Length: 57 ft 4 in (17.5 m)
  • Rotor diameter: 38 ft 0 in (11.6 m)
  • Wingspan: 45 ft 10 in (14 m)
  • Width with rotors: 84 ft 7 in (25.8 m)
  • Height: 22 ft 1 in/6.73 m; overall with nacelles vertical (17 ft 11 in/5.5 m; at top of tailfins)
  • Disc area: 2,268 ft² (212 m²)
  • Wing area: 301.4 ft² (28 m²)
  • Empty weight: 33,140 lb (15,032 kg)
  • Loaded weight: 47,500 lb (21,500 kg)
  • Max takeoff weight: 60,500 lb (27,400 kg)
  • Powerplant: 2× Rolls-Royce Allison T406/AE 1107C-Liberty turboshafts, 6,150 hp (4,590 kW) each

Performance

Armament


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