The Fascinating Technology Behind Tiltrotors

November 19, 2007 by  
Filed under Features

A tiltrotor aircraft uses rotating propellers that are designed to be tilted in order to achieve both lift and propulsion. This design gives the aircraft the vertical lift capability of a helicopter combined with the speed and range of a turboprop airplane, opening up possibilities for use both in the military and commercially.

For vertical flight, where lift is required, the tiltrotors are set at an angle that directs the thrust downwards, in the same action as a helicopter. As the aircraft’s speed increases, the pilot slowly tilts the tiltrotors forward until they are perpendicular to the ground. In this mode the aircraft is essentially a turboprop aircraft, with the wings providing the lift, enabling the aircraft to achieve speeds that are beyond the capability of a helicopter.

The major advantages of a tiltrotor aircraft over a conventional helicopter or airplane are speed and the ability to take off and land in restricted areas where no run-way is available. This is especially useful in many military situations where the overall response time is critical. Currently, the helicopter still has an advantage over a tiltrotor aircraft in terms of transport efficiency – measured at speed x payload – with the tiltrotor aircraft’s speed being achieved at the expense of payload (net carrying capacity of an aircraft).

In forward flight tiltrotors are less noisy than helicopters, reducing the possibility of detection for military purposes. However, in hovering flight, tiltrotors are as loud as an equally sized helicopter. The cruise altitude capability of tiltrotors (at least 20,000 ft) is significantly greater than that of helicopters (maximum 10,000 ft). This means that tiltrotor aircraft can be used for purposes that were limited to fixed-wing aircraft, with the added advantage of not needing a runway.

The Bell XV-3 aircraft was the pioneer in tiltrotor technology. Research began in the 1940s, with the experimental Bell XV-3 being built in 1953. This tiltrotor aircraft was used successfully until 1966, proving the tiltmotor concept to be sound while working on technical improvements for future designs. With funding from NASA and the U.S. Army, in 1972 Bell Helicopter Textron started working on a twin-engine tiltrotor aircraft, the XV-15. Two of these aircraft were built in order to explore the suitability of the tiltrotor design for civil and military operations. This proved to be the beginning of a series of developments in tiltrotor aircraft that has added a new dimension to air travel.

With rapid advances in technology and continually increasing air traffic, tiltrotor aircraft could become a common sight at airports worldwide in the future.

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