DEVELOPMENT OF A POWER SPECTRAL GUST DESIGN PROCEDURE FOR CIVIL AIRCRAFT
LOCKHEED-CALIFORNIA CO BURBANK
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Three alternate forms of gust loads criterion based on power-spectral concepts are developed. These include a mission analysis criterion, a design envelope criterion, and a criterion combining advantages of each. The latter is recommended for design use. Design levels are determined based on the strength of three existing satisfactory airplanes, the Lockheed Model 749 Constellation and Model 188 Electra and the Boeing Model 720B. The determination of a design load level involves dynamic gust analysis of the three airplanes, taking into account the significant rigid body and elastic modes, for both vertical and lateral gust inputs, as well as detailed stress analysis to the resulting loads. Two techniques were developed for integrating the statistical determination of loads with the detailed stress analysis. One is the matching condition technique, in which design conditions are generated to closely envelope the statistically defined loads, with phase relations of the various load or stress components properly accounted for. The other is the joint probability technique, in which the joint probability density of axial and shear stresses is determined at all potentially critical locations in the structure and related to the respective strength envelopes. The sensitivity of results to variations in input data is investigated.
- Civilian Aircraft