Joel B. Witte

Date of Award


Document Type


Degree Name

Master of Science in Aeronautical Engineering


Department of Aeronautics and Astronautics

First Advisor

Bradley S. Liebst, PhD


The purpose of this study was to investigate pilot-induced oscillations (PIO) and determine a method by which PIO tendency rating could be predicted. In particular, longitudinal PIO in the presence of rate-limited actuators were singled out for examination. Sinusoidal input/triangular output describing function techniques using Nichols charts were used. A new criterion dubbed Gap Criterion was calculated for PIO sensitivity. This criterion consists of the product of pilot gain necessary to cause PIO and the normalized maximum amplitude of the commanded actuator. These results were paired with simulator and flight test PIO tendency rating data. The PIO rating scale used was the PIO tendency classification of MIL-HDBK-1797. This concept was applied to two historical test databases, HAVE PREVENT and HAVE OLOP. Additional PIO data was gathered in the Large Amplitude Multimode Aerospace Simulator (LAMARS) at the Air Force Research Laboratory (AFRL), Wright-Patterson AFB, Ohio and the USAF NF-16D Variable In-flight Stability Test Aircraft (VISTA) at Edwards AFB, California. Correlation between PIO tendency rating and Gap Criterion was determined for each dataset. Most datasets exceeded a confidence level of 95% that a correlation existed. Follow-on analysis for best curve fit was also accomplished with a logarithmic fit deemed best. Datasets were combined with success to demonstrate the universality of Gap Criterion for correlating PIO tendency ratings for longitudinal PIO involving rate-limited actuators.

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