Flight Test Experience With Pilot-Induced-Oscillation Suppression Filters

Shafer, Mary F. and Smith, Rogers E. and Stewart, James F. and Bailey, Randall E. (1984) Flight Test Experience With Pilot-Induced-Oscillation Suppression Filters. Technical Report NASA TM-86028, Research Engineering, NASA Dryden Flight Research Center.

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Abstract

Digital flight control systems are popular for their flexibilty, reliability, and power; however, their use sometimes results in deficient handling qualities, including pilot-induced oscillation (PIO), which can require extensive redesign of the control system. When redesign is not immediately possible, temporary solutions, such as the PIO suppression (PIOS) filter developed for the space shuttle, have been proposed. To determine the effectiveness of such PIOS filters on more conventional, high-performance aircraft, three experiments were performed using the NASA F-8 digital fly-by-wire and USAF/Calspan NT-33 variable-stability aircraft. Two types of PIOS filters were evaluated, using high-gain, precision tasks (close formation, probe-and-drogue refueling, and precision touch-and-go landing) with a time delay or a first-order lag added to make the aircraft prone to PIO. Various configurations of the PIOS filter were evaluated in the flight programs, and most of the PIOS filter configurations reduced the occurrence of PIOs and improved the handling qualities of the PIO-prone aircraft. These experiments also confirmed the influence of high-gain tasks and excessive control system time delay in evoking pilot-induced oscillations.

EPrint Type:	NASA Technical Memorandum
Keywords:	Flight control systems, Flight test, Handling qualities, Nonlinear filters, Pilot-induced oscillation
Subjects:	Aircraft/Project: F-8 Aircraft/Project: NT-33A (01 - 09) Aeronautics: (08) Aircraft Stability And Control
ID Code:	641
Deposited On:	02 Febuary 2006
Additional Information:	18 pages. This report is a slightly revised version of AIAA Paper 83-2107, presented at the AIAA Atmospheric Flight Mechanics Conference, Gatlinburg, Tennessee, August 15-17, 1983.