In-Flight Investigtion of the Effects of Higher-Order Control System Dynamics on Longitudinal Handling Qualities

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Report Number: AFFDL TR 68-90
Author(s): Di Franco, Dante A.
Corporate Author(s): Cornell Aeronautical Laboratory, Inc.
Laboratory: Air Force Flight Dynamics Laboratory
Date of Publication: 1968-08
Pages: 195
Contract: AF 33(615)-3294
DoD Project: 8219
DoD Task: 821905
Identifier: AD0840752

The results of a flight test program to investigate the effects of higher-order control system dynamics on the handling qualities of a fighter airplane are presented and discussed. This research was undertaken using the USAF/CAL variable stability T-33 airplane as an in-flight simulator. This in-flight investigation was based on a similar fixed-base ground simulator program. Higher-order response characteristics were obtained by altering the elevator stick feel system dynamics and elevator actuator dynamics in conjunction with four different sets of longitudinal short period airplane dynamics. In the investigation, the dynamics of any of the three elements (feel system, actuator, and airplane) could be changed independently of the others. Three of the set of four airplane characteristics were investigated as a fighter in 'up-and-away' flight, and the fourth was evaluated as a fighter during landing approach. Thirty-two different configurations were evaluated by one CAL evaluation pilot (Pilot B) and 35 configurations were evaluated by a second CAL evaluation pilot (Pilot H). Essentially the same configurations were evaluated by both pilots and rated using a new pilot rating scale. Pilot H also rated the configurations for their pilot-induced oscillation (PIO) tendencies using a PIO rating scale. Pilot comments were recorded in flight and the comments and ratings were related to various handling qualities parameters and response characteristics of the configurations. The results of the investigation indicate that many of the higher-order control systems investigated produce very pronounced PIO tendencies and these tendencies can be related to the delay in the initial response of the airplane and to the stick force gradients. Configurations that were acceptable with conventional control system dynamics were considered unflyable with certain higher-order characteristics.

Provenance: Bombardier/Aero

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