Rotorcraft Airframe Load Spectrum Development

This paper provides an overview of analytical tools and methods for developing airframe load spectra at the Rotorcraft Division of Boeing. Legacy methods for airframe and dynamic component loads provide the foundation for improved airframe methods that include low-cycle maneuver sequence loading as well as high-cycle vibratory loading. Different simulation models have been developed to calculate external loads associated with flight maneuvers, landing maneuvers and vibratory loads. Each simulation has been validated to some degree through comparisons with full-scale vehicle test data, although additional work remains to be done. Methods for applying these loads to airframe fatigue and damage tolerance design have been defined that overcome limitations of the current simulation capabilities.