English

Abstract

Transoceanic jet transport service, once the exclusive domain of four-engine airplanes, will continue the trend toward two-engine airplanes. This has become possible due to larger, more fuel-efficient and reliable engines and airplanes. Improved reliability demonstrations may soon permit two-engine airplane tracks as far as 120 and 180 minutes flying time from the nearest suitable diversion airport. Although the probability of diversion for a given flight is extremely remote, safety dictates a worst case fuel reserve scenario based on engine-out diversion from the furthest point. This study focuses on engine-out optimum range flight techniques for typical two- and four-engine transports. Various engine-out scenarios for the Boeing 767 and Boeing 747 were investigated using airplane models in wind tunnel experiments. Engine-out specific range improvements up to 9% appear possible through proper techniques of zero sideslip, minimum drag flight. During a rare actual diversion, following proper minimum drag techniques will optimize engine-out specific range and stretch onboard reserves. Similarly, knowledge of such efficiency gains could routinely be translated into reduced diversion fuel reserves--without reduction in safety margin. Reduced contingency fuel translates to some combination of increased payload or improved all-engine cruise economy, thereby increasing operating efficiency and profitability.