332. Weight and Balance Considerations for Supersonic Aircraft Design and Operation
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Paper
Abstract
This paper was presented at the Twenty-first Annual National Conference of the Society of Aeronautical Weight Engineers at Seattle, Washington, May 14-17, 1962. The present widespread interest in supersonic transport aircraft has spawned a number of design studios, which, from the viewpoint of the weight engineer, appear to contain certain weight and balance inconsistencies. The intent of this paper is to point out, using available weight data, the current and predicted weight trends peculiar to supersonic designs, and in particular, the weight growth trends of supersonic transports. It is further intended to present supersonic weight and balance data, in a comparative manner, which may be used as guides, goals and measuring devices for supersonic aircraft designs of the future.
Weight efficiencies of supersonic aircraft are falling below present subsonic designs, at similar payloads and gross weights, caused mainly by stringent system requirements added in the interests of safety, reliability, passenger comfort, and efficient operation. Desired supersonic range is obtained by using increasingly larger amounts of fuel for decreasingly smaller gains in weight efficiency. Thus, there is a rapid growth of gross weight with lesser gains in weight efficiency or ratio of gross weight to dry weight. Resulting gross weights can only be reduced by ingenious, light weight s structure and systems, and increased velocity-to-specific fuel consumption and lift-to-drag ratios.
The balance problem has been found to be more important for supersonic aircraft than it was in subsonic designs; as a result, this problem must be studied in detail early in the configuration selection studies. As the aircraft approaches supersonic speeds, the aerodynamic center moves rapidly aft, and remains appreciably aft of subsonic aerodynamic centers, throughout supersonic flight. A nearly equal aft shift of airplane center-of-gravity is required to prevent the use of high trimming forces that result in increased supersonic drag.
It is concluded that weight and balance considerations must be given accurate and specific attention early in the evaluation of supersonic designs, to preclude the waste and confusion caused by overly optimistic weight estimates, and to insure realistic airframe configurations.
