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Effects of Flight Load Spectrum Perturbations on Cost and Fatigue

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Rotary‐ and fixed‐wing aircraft owners rarely operate their aircraft the way aircraft manufacturers envisaged during design. The effects of perturbing the amount of time spent in flight conditions, on both component fatigue damage and life‐cycle costs, are investigated in this article. Seemingly small perturbations in flight hours can lead to large changes in fatigue and costs. A set of influence coefficients are developed to determine the effects of spectrum perturbations on both fatigue and cost. These influence coefficients give both qualitative (“importance” ordering) and quantitative (sensitivity) information regarding all flight conditions. The resulting procedure is easy both to implement and use, and allows the operator to determine the effects of different spectra on both damage and cost. In deriving these results only three assumptions are made: costs vary continuously with time, Miner's rule is valid, and the fatigue damage calculated for the original usage spectrum is correct. As an example, the design spectrum of a Black Hawk helicopter is perturbed, and the resulting fatigue and cost effects are investigated. The outlined procedures have the potential to return large cost savings and safety improvements for both rotary‐ and fixed‐wing aircraft operators.

Document Type: Research Article


Affiliations: Defence Science and Technology Organisation, Melbourne, Australia

Publication date: April 1, 2003

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  • The Journal of the American Helicopter Society is the world's only scientific journal dedicated to vertical flight technology. It is a peer-reviewed technical journal published quarterly by AHS International and presents innovative papers covering the state-of-the-art in all disciplines of rotorcraft design, research and development. (Please note that AHS members receive significant discounts on articles and subscriptions.)

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