Due to the increasing costs of experimental testing, analytical methods are becoming the primary means of demonstrating structural integrity, durability, and crashworthiness of helicopter structures, both for civil and military use, when representative conditions such as temperature, moisture, cyclic loading, and impact have to be considered. The airframes of derivatives of the basic BO 105 have been qualified in the past without retesting because it could be shown that the structure conformed to those for which experience had demonstrated the structural analysis to be reliable. During the development of a composite fuselage for the BK 117, both an analytical and an experimental strength substantiation was performed, which corresponded very well and formed the basis for airworthiness qualification of this experimental helicopter under flight testing now. A large number of components in the dynamic system are designed primarily so that they will provide adequate fatigue strength, defined in terms of an endurance limit, or in terms of fatigue life. The analytical qualification of these fatigue critical structures, on the basis of measured fatigue loadings and calculated working S-N curves, is state-of-the-art in the helicopter industry. In the nonlinear domain, analytical methods are applied for highly laminated elastomeric bearings and for the crashworthiness qualification of both crushable subcomponents and complete helicopters. The results gained so far allow the application of analytical methods, partly in combination with coupon or component testing, for the qualification of helicopter structures.
Analytical Methods for the Qualification of Helicopter Structures
1991
14 pages
Report
Keine Angabe
Englisch
Aircraft , Structural Mechanics , Aircraft reliability , Airframes , Cyclic loads , Fatigue life , Flight tests , Fuselages , Helicopters , Qualifications , Structural analysis , Structural failure , Costs , Crashworthiness , Durability , Elastomers , Moisture , Nonlinearity , S-n diagrams , Foreign technology
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