AERODYNAMIC TECHNOLOGY APPLIED TO TAKEOFF AND LANDING

Achieving adequate low-speed aerodynamic characteristics for takeoff and landing of modern, high-performance airplanes is one of the most challenging goals of subsonic aerodynamic technology. This paper shows the need for a high degree of refinement in the aerodynamics of the low-speed flight regime, some areas where more fundamental knowledge is needed to obtain such a degree of accuracy, and how the requirements of engineering application and flight safety modify the characteristics apparently available from the standpoint of pure science. I t does not present the solution to any aerodynamic problems. Instead, it points out areas where further work remains to be done. Its objective is to put some engineering perspective on the goals and results of the aerodynamic scientist. The need for accurate knowledge of low-speed aerodynamic performance is demonstrated by showing the extreme leverage that small changes in lift and drag exert on the payload and economics of commercial airplanes. Several typical areas are discussed where increased knowledge is needed for better understanding of airplane takeoff and landing characteristics. Included is the problem of propeller and jet-powered STOL airplanes in descent, with their associated jetand slipstream-interference effects. Also included are groundproximity effects on the lift and trim of tailed and delta configurations. Engineering application of scientific knowledge is demonstrated through the example of a transport airplane equipped with a powerful boundary-layer control (BLC) flap system. With the raw wind-tunnel data as the basic scientific knowledge, the performance of the system installed on an airplane is developed. Installation losses, safety requirements, and operational considerations such as descent rates and go-around capability are examined as to their effect on flap design and operational philosophy.