Studies of Time-Phased Vertical and Lateral Gusts: Development of Multiaxis One-Minus-Cosine Gust Model

摘要

At a Gust Specialists meeting convened by the Federal Aviation Administration (FAA) in 1998, a multiaxis extension of the existing tuned isolated discrete-gust (IDG) method (1-cosine profile) incorporating a pair of vertical and lateral one-minus-cosine gusts was proposed. A particular application of this method is the gust response of wing-mounted nacelles. This report presents the theoretical and empirical basis for this gust model, including results from a statistical analysis of measured turbulence data in support of the use of an 'amplitude-reduction' factor which relates the magnitudes of the gust components in the multiaxis model to the magnitude of a single (1-cosine) gust in one axis as defined in the current tuned isolated discrete-gust requirement. On this basis, a proposal is made for the possible form of an associated airworthiness rule. Applications of this method to the engine nacelle responses of an Airbus-type aircraft dynamic model are presented and the resulting predicted loads compared with those resulting from the multiaxis PSD method and from a round-the-clock isolated discrete-gust analysis. A statistical analysis is also presented of the engine nacelle loads resulting when the same aircraft dynamic model is subjected to measured turbulence inputs and these loads are compared with the predicted loads resulting from the proposed multiaxis analysis method.