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