NASA TP 1760 – Economic Evaluation of Flying-Qualities Design Criteria for a Transport Configurated with Relazed Static Stability

In Professional by Steve Sliwa


An optimal design program with constrained parameter optimization has been shown to be useful in evaluating the impact of certain flying-qualities design assumptions and in determining the sensitivity to several related parameter variations. Transports optimally configured with relaxed static stability showed a potential savings in direct operating cost of 1.4 percent when compared with transports with conventional static margins. This corresponded to a fuel savings of 4.2 percent for the medium-range mission considered. Savings of nearly 1 percent in direct operating cost were also possible from utilizing half the nominal center-of-gravity range of travel and from allowing the landing gear to be structurally dislocated from the wing. Requiring transports to be able to take off with the stabilizer trimmed in the most adverse position was shown to penalize the aircraft over 4 percent in direct operating cost.

During the course of this study, it became obvious that there is a need for developing design criteria for the minimum flying qualities that are necessary for specifying the inherent stability and control characteristics of augmented transports. Most existing criteria did not have useful parameters for defining handling qualities of inherently unstable transports that rely upon augmentation systems. Furthermore, few flying-qualities data were available in terms of factors that would be useful for developing appropriate inherent longitudinal-handling-qualities design criteria for transports configured to take maximum advantage of relaxed-static-stability augmentation systems.

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