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Frequency Domain Flight Testing and Analysis of an OH‐58D Helicopter

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A demonstration of frequency domain flight testing techniques and analysis was performed on a U.S. Army OH‐58D helicopter. The tests were conducted in support of the OH‐58D Airworthiness and Flight Characteristics Evaluation and the Army's development and ongoing review of Aeronautical Design Standard, ADS‐33C, Handling Qualities Requirements of Military Rotorcraft. Hover and forward flight (60 knots) condition tests were conducted in three flight hours by Army experimental test pilots. Bandwidth and phase delay parameters were determined from flight test data according to the definitions in the ADS‐33C. A frequency rcsponse identification program (FRESPID) was used to derive the required parameters using a discretized fast‐Fourier transform algorithm on input control deflections and integrated output airframe angular rates. A comparison was made between handling qualities ratings from airworthiness evaluations and the predicted handling qualities levels from ADS‐33C using the derived bandwidth and phase delay. In general, there was excellent agreement, indicating the validily of the frequency‐response concept for predicting handling qualities levels.

Document Type: Research Article


Affiliations: Airworthiness Qualification Test Directorate, U.S. Army Aviation Technical Test Center, Fort Rucker, Alabama

Publication date: 1992-10-01

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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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