A Theory for Longitudinal Short-Period Pilot Induced Oscillations

Item

Title
A Theory for Longitudinal Short-Period Pilot Induced Oscillations
Creator
Smith, Ralph H.
Date
1977
Identifier
ADA056982
ADA056982
Abstract
This report presents a theory for longitudinal, short-period, pilot-induced oscillations (PIO). The theory explains how the airplane's pitch attitude and normal acceleration modes can couple with pilot dynamics to produce large-amplitude, uncontrollable oscillations. The effects of control system dynamics and feel system nonlinearities are encompassed by this theory. It is concluded that an airplane's potential for PIO can be determined based entirely on linear systems analysis; the prediction of fully-developed PIO frequency and amplitude requires that all significant nonlinearities be considered. The theory postulates that PIO can develop either as a result of closed loop control of pitch attitude or from abrupt control or atmospheric inputs of size sufficient to excite a lightly damped, dominant, stick-free airplane mode. A number of PIO case histories are examined; it is shown that these confirm the proposed theory. The implications of the theory to flight test and to simulation are discussed. A generalized definition for PIO is given which permits distinctions to be made between pilot-vehicle system oscillations due only to attitude control and those due to attitude plus path control modes. It is suggested that the theory can be easily extended to the study of lateral-directional PIO. A bibliography of PIO source material is included with this report.
Date Issued
1977-06
Extent
141
Corporate Author
Systems Research Laboratories, Inc.
Laboratory
Air Force Flight Dynamics Laboratory
Report Number
AFFDL-TR-77-57
Contract
F33615-77-C-3011
DoD Project
8219
DoD Task
821904
Distribution Conflict
No
Access Rights
Approved for public release; distribution unlimited
Photo Quality
Not Needed
Distribution Classification
1
DTIC Record Exists
Yes
Report Availability
Full text available by request
NTRL Accession Number
ADA056982
Provenance
University of Colorado Colorado Springs, Kraemer Family Library
Type
report

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