1992-10-01

The Tilt Wing Advantage - For High Speed VSTOL Aircraft 921911

By the early 21st century, high speed VSTOL aircraft will be operating in Air Transportation Systems around the world moving people and cargo to and from thousands of public use vertiports and stolports. Of even greater significance is the fact that high speed VSTOL aircraft will be playing a major role in reducing traffic congestion on the ground and in the air at busy hub airports.
For many years world wide attention has been drawn to the United States' effort to develop the military V-22 Osprey. More than two billion dollars have been expended on this tilt rotor program. The advantages of a tilt wing over a tilt rotor, however, are beginning to surface in both the United States and abroad. The tilt wing, it turns out, is more efficient, more cost effective, safer and an easier aircraft to operate.
Tilt wing development began in the mid 1950's. Successful demonstrator aircraft were the Boeing Vertol 76 VZ-2, the Hiller X-18, the LTV/Hiller/Ryan XC-142A and the Canadair CL-84. In the mid 1970's military support for this form of power lift decreased. Also, there was no obvious need at the time for civil high speed VSTOL aircraft. Now there is.
Tilt rotor studies began in the mid 1940's by the Bell Helicopter Company. Bell's first test aircraft was the XV-3. Their second tilt rotor aircraft was the XV-15. The military V-22 Osprey is a combined Bell-Boeing tilt rotor program.
This paper brings into focus the technical and operational advantages of the tilt wing concept in comparison with the tilt rotor, the helicopter and conventional airplanes. The following areas are discussed and analyzed: Public Acceptance, Block Time, Direct Operating Cost, Useful Load and Payload, Vertical Lift, Propulsive Efficiency, Pilot Transition, Reliability Maintenance and Safety, Development and Production cost, Structural Dynamics, CTOL/VTOL/STOL and STOVL operations, and Search and Rescue (SAR).
A 9 passenger (11 seats) high speed VSTOL tilt wing aircraft is proposed for entry into the civil market by the late 1990's. It will be certificated in the U.S. under the FAA's “Airworthiness Criteria for the Powered-Lift Normal Category Aircraft” which applies to “nine or fewer passenger seats”.
A 14 passenger (16 seats) tilt wing vehicle that will require certification under the FAA's “Airworthiness Criteria for Powered Lift Transport Category Aircraft” is currently in development by another company.

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