Analysis of the longitudinal handling qualities and pilot-induced-oscillation tendencies of the High-Angle-of-Attack Research Vehicle (HARV)

19950016877 · NASA · 1994

Public domain · NASATechnical Reports

Overview

The NASA High-Angle-of Attack Research Vehicle (HARV), a modified F-18 aircraft, experienced handling qualities problems in recent flight tests at NASA Dryden Research Center. Foremost in these problems was the tendency of the pilot-aircraft system to exhibit a potentially dangerous phenomenon…

Publisher: NASA
Document: 19950016877
Year: 1994
Pages: 1

Key points

The High-Angle-of-Attack Research Vehicle (HARV) is a modified F-18 aircraft that experienced handling qualities problems during flight tests.
The primary issue identified was the tendency for pilot-induced oscillations (PIO), which can severely restrict performance and mission capabilities.
A pilot/vehicle analysis was conducted to reduce PIO tendencies and improve overall handling qualities with minimal changes to existing flight control laws.
The analysis led to the development of a control stick command shaping filter, which showed significant improvements in handling qualities and PIO tendencies.
The modified control system is awaiting evaluation in a real-time, pilot-in-the-loop simulator at Langley.

Frequently asked questions

What is the main issue identified with the HARV during flight tests?

The main issue identified was the tendency for pilot-induced oscillations (PIO), which can severely restrict performance and mission capabilities.

What was the goal of the pilot/vehicle analysis conducted on the HARV?

The goal of the pilot/vehicle analysis was to reduce PIO tendencies and improve overall vehicle handling qualities with as few changes as possible to the existing flight control laws.

What solution was developed to improve the handling qualities of the HARV?

A control stick command shaping filter was developed, which indicated significant improvements in handling qualities and PIO tendencies.

Where is the modified control system of the HARV currently being evaluated?

The modified control system is currently awaiting evaluation in the real-time, pilot-in-the-loop Dual-Maneuvering-Simulator (DMS) facility at Langley.

What are the potential consequences of pilot-induced oscillations (PIO)?

PIO can severely restrict performance, sharply diminish mission capabilities, and can even result in aircraft loss.

Document

199K,,/ p77

N95- 23297

Handling Qualities Analysis of the Longitudinal and Tendencies of the Pilot-Induced-Oscillation Vehicle (HARV) High-Angle-of-Attack Research by Ronald A. Hess Department of Mechanical and Aeronautical Engineering University of California Davis, CA 95616 The NASA High-Angle-of Attack Research Vehicle (HARV), a modified F-18 aircraft, experienced handling qualities problems in recent flight tests at NASA Dryden Research Center. Foremost in these problems was the tendency of the pilot-aircraft system to exhibit a potentially dangerous phenomenon known as a pilot-induced oscillation (PIO). When they occur, PIO's can severly restrict performance, sharply dimish mission capabilities and can even result in aircraft loss. A pilot/vehicle analysis was undertaken with the goal of reducing these PIO tendencies and improving the overall vehicle handling qualities with as few changes as possible to the the existing feedback/feedforward flight control laws.

Utilizing a pair of analytical pilot models developed by the author, a pilot/vehicle analysis of the existing longitudinal flight control system was undertaken. The analysis included prediction of overall handling qualities levels and PIO susceptability. The analysis indicated that improvement in the flight control system was warranted and led to the formulation of a simple control stick command shaping filter. Analysis of the pilot/vehicle system with the shaping filter indicated significant improvements in handling qualities and PIO tendencies could be achieved. A non-real time simulation of the modified control system was undertaken with a realisitc, nonlinear model of the current HARV. Special emphasis was placed upon those details of the command filter implementation which could effect safety of flight. The modified system is currently awaiting evalutation in the real-time, pilot-in-the-loop, Dual-Maneuvering-Simulator (DMS) facility at Langley.