Development of a BLC high-lift system for high-speed airplanes.

Abstract

This paper presents the significant steps in the development of a boundary-layer control (BLC) high-lift system for the 367-80 (707 prototype) airplane. The design is based on an advanced boundary-layer control concept using an ejector for momentum augmentation of BLC air and primary air bleed from the propulsion system. A modulated thrust reverser for flight-path control has been integrated into the over-all design. Considerations leading to the selection of the design concept are discussed, and the importance of a well integrated program of aerodynamic and mechanical system development is shown. Pertinent results of research involving two-dimensional and complete configuration tests in the wind tunnel and full-scale ejector tests in the laboratory are given. A recently completed, joint flight research program by Boeing and NASA shows that large gains in low-speed performance can be made with blowing boundary-layer control. Landing speeds less than 85 knots at 140,000 Ib airplane gross weight have been consistently achieved. Careful flight evaluation shows that conventional aerodynamic controls with stability augmentation can provide satisfactory handling characteristics for large jet airplanes throughout the extended low-speed flight envelope.