V-22 Osprey

AV8-B Harrier II

Powered lift or powered-lift refers to a type of aircraft that can take off and land vertically and functions differently from a rotorcraft in horizontal flight.

The term is particularly used by the United States Federal Aviation Administration for classification purpooses. Powered-lift is one of the seven categories of aircraft designated by the the Federal Aviation Administration; the other six being Airplane, Rotorcraft, Glider, Lighter-Than-Air, Powered parachute, and Weight-shift-control.

Powered-lift means a heavier-than-air aircraft capable of vertical takeoff, vertical landing, and low speed flight that depends principally on engine-driven lift devices or engine thrust for lift during these flight regimes and on nonrotating airfoil(s) for lift during horizontal flight.

—FAA^[1]

The first powered-lift ratings to be issued by the FAA on a civilian pilot certificate were on 21 August 1997, to pilots of Bell Helicopter and Boeing, and of the United States Marine Corps.^[2]

[edit] Compound rotorcraft

A compound rotorcraft has both a lifting rotor and fixed wings (although in the USA, the term "compound rotorcraft" officially refers to a mixed powerplant system).

Some types have a ducted rotor design, in which the rotor is surrounded by a large ring-shaped duct to reduce tip losses. Typically, the rotor swings forward to act as a propeller in forward flight. The difference between a ducted rotor and a ducted fan design is that when the rotor is stationary you can see through the rotor disc.^{[citation needed]}

[edit] Tiltrotor

A USAF CV-22 in flight

The powered rotors of a tiltrotor (sometimes called proprotor) are mounted on rotating shafts or nacelles at the end of a fixed wing, and used for both lift and propulsion. For vertical flight, the rotors are angled to provide thrust upwards, lifting the way a helicopter rotor does. As the aircraft gains speed, the rotors progressively rotate or tilt forward, with the rotors eventually becoming perpendicular to the fuselage of the aircraft, similar to a propeller. In this mode, the wing provides the lift and the rotor provides thrust. The wing's greater efficiency helps the tiltrotor achieve higher speeds than helicopters.

The V-22 Osprey by Bell Helicopter/Boeing, a twin-engine tiltrotor design that has two turbine-powered engines driving three-bladed rotors. The rotors function similar to a helicopter in vertical flight, and similar to an airplane in forward flight. The aircraft first flew on 19 March 1989.

The Bell/Agusta BA609 tiltrotor is the evolution of Bell Helicopter's V-22 Osprey into a civilian aircraft. The aircraft can take off and land vertically with 2 crew and 9 passengers, and within 20 seconds, transition to forward flight (by tilting its rotor blades into a fully forward position, much like the V-22 Osprey). In forward flight it can cruise at speeds of up to 275 knots (509 km/h), with a range exceeding 1,000 nautical miles (with long-range fuel tanks). It is rated to fly above FL210 (21,000 ft), has a maximum payload capacity of over 5,500 pounds, thanks to two Pratt and Whitney PT6C-67A turbines rated at 1,940 shp, each driving a 26-foot (8 m) diameter 3-bladed rotor blade. The aircraft is not yet in full production; however, over 80 orders have been taken.

[edit] Tiltwing

The Vertol VZ-2 was a research aircraft developed in the late 1950s. Unlike other tiltwing aircraft, Vertol designed the VZ-2 using rotors in place of propellers.^[3] On 23 July 1958, the aircraft made its first full transition from vertical flight to horizontal flight. By the time the aircraft was retired in 1965, the VZ-2 had accomplished 450 flights, including 34 full transitions.

[edit] Helicopter-airship compounds

Piasecki Helicopter developed the Piasecki PA-97 Helistat using the rotor systems from four obsolete helicopters and a surplus Navy blimp, in order to provide a capability to lift heavier loads than a single helicopter could provide. The aircraft suffered a fatal accident during a test flight. In 2008, Boeing and SkyHook International resurrected the concept and announced a proposed design of the SkyHook JHL-40.

[edit] Other rotorcraft hybrids

Some aircraft take off vertically as a rotorcraft. The rotor then transitions to an alternative lifting mode for horizontal flight.

[edit] Triebflugel

The Focke-Wulf Fw Triebflügel was a design by Nazi Germany to utilize pulsejets to power a rotor that rotated about the fuselage axis behind the cockpit. Similar to a coleopter aircraft, the Triebflügel took off and landed on its tail and then rotated forward on the pitch axis after takeoff and acceleration for forward flight. The design was never been built beyond model wind tunnel testing, due to Allied bombing of the development facilities.

[edit] X-wing

The Sikorsky X-Wing had a rotor utilizing compressed air to control lift over the surfaces while operating as a helicopter. At higher forward speeds, the rotor would be stopped to continue providing lift as tandem wings in an X configuration. The program was canceled before the aircraft had attempted any flights with the rotor system.

[edit] Jet lift

[edit] Tail-sitters

The SNECMA Coléoptère featured an annular wing. The whole aircraft points vertically for takeoff and, in theory, then tilts horizontally for forward flight. The transition to forward flight has never been achieved.

[edit] Vectored thrust

The Harrier Jump Jet covers a series of a military VSTOL jet aircraft. It is capable of vertical/short takeoff and landing (V/STOL) and is the only truly successful design of this type from the many that arose in the 1960s. These aircraft are capable of operating from small spaces,such as fields, roads, and aviation-capable ships.

[edit] See also

• Canadair CL-84
• F-35 Lightning II
• Pilot certification in the United States

[edit] Notes

[edit] References

• "Addressing the future challenges of the operation of powered lift category/tiltrotor class aircraft in international air navigation", report by "Assembly – 35 Session Executive Committee", www.faa.gov
• "Vertical flight technology in the national airspace system", Testimony of William Wallace, the National Resource Specialist for Rotorcraft Operations of the Federal Aviation Administration, before the Subcommittee on Space and Aeronautics, 9 May 2001, http://testimony.ost.dot.gov