CIVIL TILTROTOR AIRCRAFT: A COMPARISON OF FIVE CANDIDATE DESIGNS

Commercial interest in the tiltrotor configuration stems from the synergy of VTOL operation with turboprop comfort, speed, and cruise efficiency. During 1986-87, NASA, FAA, and DOD funded a study titled, "Civil Tiltrotor Missions and Applications: A Research Study." Results showed that a substantial share of the Northeast Corridor shorthaul market may be captured by civil tiltrotor (CTR) aircraft with strategically located, IFR-cerified vertiports. Bell Helicopter Textron and Boeing Helicopters participated under the direction of Boeing Commercial Airplanes by developing CTR vehicle concepts. A status of tiltrotor technology is presented herein with a brief discussion of the market segments, VTOL intercity transport system, and vertiport concepts. Mission profiles and design ground rules were established based on existing Federal Aviation Regulations, including the unprecedented ability to hover at design gross weight with one engine inoperative. Two baseline configurations were evolved from existing tiltrotor products: an 8-passenger executive tiltrotor (XV-15 size) and a 31-passenger commuter (V-22 variant). Additional concepts included a 19-passenger commuter, a 39-passenger commuter, and a 75-passenger transport. Trade studies included variations in seating arrangement, wing placement, nacelle configuration, and canards versus conventional layouts. Performance summaries are presented for all configurations in both VTOL and STOL operations.