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 purposes. Powered-lift is one of the seven categories of aircraft designated by the Federal Aviation Administration; the other six being Airplane, Rotorcraft, Glider, Lighter-Than-Air, Powered parachute, and Weight-shift control. 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.

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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 Bell Boeing V-22 Osprey by Bell Helicopter and Boeing is a twin-engine tiltrotor design that has two turbine engines each driving three-blade rotors. The rotors function similar to a helicopter in vertical flight, and similar to an airplane in forward flight.

It first flew on 19 March 1989. The AgustaWestland AW609 (formerly Bell/Agusta BA609) tiltrotor is civilian aircraft based on the V-22 Osprey. The aircraft can take off and land vertically with 2 crew and 9 passengers. The aircraft is expected to be certified in 2017. A Tail-sitter is an aircraft that rests on the ground pointing vertically upwards, so that it rests on its tail and takes off and lands vertically. Celsa Practice Test Pdf.

The whole aircraft then tilts forward horizontally for normal flight. No type has ever gone into production, although a number of experimental variants have been flown, using both proprotor and jet thrust.

Some have achieved successful transition between flight modes. The coleopter type has an annular wing forming a duct around a lift rotor. The transition to forward flight has never been achieved, although the SNECMA Col?opt?re took off, hovered and landed vertically.

The German Focke-Wulf Fw Triebfl?gel was a design studied during the Second World War. It used pulse jets to power a rotor that rotated about the fuselage axis behind the cockpit. Similar to a coleopter fixed-wing aircraft, the Triebfl?gel was intended to take off and land on its tail, rotating on the pitch axis after takeoff and acceleration for forward flight. The design was never been built beyond model wind tunnel testing. One of the major problems with the early tiltrotor aircraft designs was that the driveshafts carrying power from the fuselage out to the wingtip rotors, along with the gearbox and tilting mechanisms at the wingtips, had substantial loads placed upon them and were heavy. They were transferring large amounts of power and torque long distances for an aircraft power transmission system. The XV-15 experimental aircraft introduced a major design concept advance: instead of engines in the fuselage, the XV-15 moved the engines out to the rotating wingtip pods, directly coupled to the rotors.

The normal path for power was directly from the engine into a speed-reduction gearbox and into the rotor/propeller without any long shafts involved. There was still a driveshaft along the wings for emergency use to transfer power to the opposite rotor in case of engine failure, but that shaft did not normally carry any power loads, making it lighter. The tilting engine concept introduced complexities in the design of the engines and engine pods to be able to shift from operating horizontally to operating vertically. Those problems were addressed fairly early in the XV-15 program. In the late 1960s and early 1970s, NASA and other researchers worked extensively on theoretical and wind tunnel tests of various rotor pods.

Two companies were involved in the research and proposing designs: Bell Helicopter and Boeing-Vertol. The focus was on tilt rotor pods, integration of the tilting rotors with the wings and fuselage of the aircraft, and studying the airflow as the rotors tilted. Tilt rotors with fixed rotors and with folding rotors were investigated. Unduh Melahirkan Kembar there.