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Meeting	ACGS Committee Meeting 133 - Asheville, NC - November 2024
Agenda Location	5 SUBCOMMITTEE A – AERONAUTIC AND SURFACE VEHICLES 5.1 PIO and Handling Qualities Prediction Using the USAFTPS Bjorkman PIO Data Set
Title	PIO and Handling Qualities Prediction Using the USAFTPS Bjorkman PIO Data Set
Presenter	Ed Bachelder
Affiliation	San Jose State University
Available Downloads*	presentation
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Abstract	A key objective of this work was to develop a quantitative rationale to explain some aspects of pilot rating variability, as this could explain the salient pilot-vehicle response characteristics that may be hidden when averaged ratings are used as a handling qualities metric. This paper hypothesizes that the factors affecting a pilot’s ability to stabilize and control an aircraft following abrupt control motion are neither the damping nor the frequency of the ensuing oscillation, but rather the length of time that the oscillation remains large enough to interfere with the task (i.e., the product of damping and frequency). A handling qualities metric called the decay rate parameter that reflects the decay rate of the closed loop dominant mode is introduced. Closed loop pilot-vehicle oscillation decay rates were generated using a pilot model employing pitch (visual channel) and pitch rate (vestibular channel) tracking strategies. These decay rates were used to predict minimum and maximum handling qualities ratings and pilot induced oscillation (PIO) ratings. The predicted ratings closely matched actual pilot ratings from an inflight PIO study using the USAF variable stability NT-33A aircraft. The pilot model also predicted the inflight PIO frequencies closely. Predicted handling qualities and PIO ratings also closely matched the actual ratings from a piloted NASA Vertical Motion Simulator study that replicated the inflight study. The results indicate that even with the highest fidelity motion simulation, pilot control response is influenced primarily by the visual channel and is, therefore, constrained by its inherent limitations. Conversely, the dominant control strategy appears to be the vestibular channel when pilots conduct a visual task that is anchored in the physical, out-the-window environment. The vestibular channel is shown to incur effectively no time delay.