Computer Techniques for the Rapid Flutter Clearance of Aircraft Carrying External Stores. Part I. Perturbation Theory and Applications

摘要

A method for rapid flutter clearance of aircraft is developed and is demonstrated in Part I of this report. The analytical perturbation procedures are mechanized by means of a data retrieval system and computer program documented in a separate cover in Part II of the report. The demonstration studies were conducted for the production F-5 aircraft using perturbations covering a range of external stores representative of the major part of the USAF stores inventory. The perturbation flutter program has been used for typical production applications with resulting execution speeds of 1000 analyses per hour. The perturbation method produced execution time savings of approximately 90% for the IBM 370/165 central processor employed in the demonstration studies. Comparable savings are expected for other large processors such as the CDC 6600 and 7600. Significantly larger time savings are expected for problems involving more sophisticated finite element models. Flutter boundaries were compared by both the perturbation method and the conventional methods. Comparisons show satisfactory agreement for most design purposes. In many cases involving moderate perturbations, different branches of a stability boundary were reached from a single baseline case with extreme accuracy. Perturbations involving changes of up to 300% in store inertias were studied. The method has the capability to screen many configurations rapidly and to identify significant problem areas for detailed study.