An In-flight Investigation of Pilot-induced Oscillation Suppression Filters During the Fighter Approach and Landing Task
An In-flight Investigation of Pilot-induced Oscillation Suppression Filters During the Fighter Approach and Landing Task

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Published: 1982

Total Pages: 154

ISBN-13:

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An investigation of pilot-induced oscillation suppress ion (PIOS) filters was performed using the USAF/Flight Dynamics Laboratory variable stability NT-33 aircraft, modified and operated by Calspan. This program examined the effects of PIOS filtering on the longitudinal flying qualities of fighter aircraft during the visual approach and landing task. Forty evaluations were flown to test the effects of different PIOS filters. Although detailed analyses have not been undertaken, the results indicate that PIOS filtering can improve the flying qualities of an otherwise unacceptable aircraft configuration (Level 3 flying qualities). However, the ability of the filters to suppress pilot-induced oscillations appears to be dependent upon the aircraft configuration characteristics. Further, the data show that the filters can adversely affect landing flying qualities if improperly designed. The data provides an excellent foundation from which detail analyses can be performed.

Suppression of Pilot-Induced Oscillation (PIO)
Suppression of Pilot-Induced Oscillation (PIO)

Author: Donald A. Johnson

Publisher:

Published: 2002-03-01

Total Pages: 203

ISBN-13: 9781423512158

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Closed loop instability caused by excess phase lag induced by actuator rate limiting has been suspected in many pilot-induced oscillations (PIOs) and oscillatory departures from controlled flight. As part of the joint AFIT/TPS program, a longitudinal pilot command notch filter activated by a real- time oscillation verifier (ROVER) algorithm was developed to eliminate the PIO source for any developing, severe PIO. Closed loop computer simulations were conducted to prepare for the flight test. The HAVE ROVER flight test project was flown using the NF-16D Variable Stability In-flight Simulator Test Aircraft (VISTA). A programmable heads-up display (HUD) was used to generate a tracking task simulating Category A fighter maneuvers. 6 of the 12 evaluation sorties were flown against an airborne target aircraft. Flight test results showed the stick filter was pivotal in preventing aircraft oscillatory departures and suppressing PIOs. With the original threshold settings, the ROVER algorithm correctly characterized pilot observations of the aircraft motion 72% of the time. Further analysis indicated that a high false detection rate was responsible for this relatively low correct detection rate. These results suggested that the threshold values used by ROVER to detect PIO were set too low. By varying the threshold values as part of a parametric study, a maximum overall correct detection rate of 82% was attained.

A Nonlinear Pre-Filter to Prevent Departure And/or Pilot-Induced Oscillations (PIO) Due to Actuator Rate Limiting
A Nonlinear Pre-Filter to Prevent Departure And/or Pilot-Induced Oscillations (PIO) Due to Actuator Rate Limiting

Author: Michael Chapa

Publisher:

Published: 1999-03-01

Total Pages: 155

ISBN-13: 9781423546306

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Closed loop instability caused by excess phase lag induced by actuator rate limiting has been suspected in many aircraft departures from controlled flight and pilot-induced oscillations (PIO). As part of the joint Air Force Institute of Technology Test Pilot School (AFITITPS) program, a nonlinear rate limiter pre-filter (RLPF) was developed to minimize the phase lag induced by rate limiting. RLFF performance was evaluated inside the feedback path, but primary emphasis was on the pilot command path. Closed loop computer and motion- based flight simulation were conducted to prepare for the flight test. The HAVE FILTER flight test project was flown using the NF-16D Variable Stability in- flight Simulator Test Aircraft (VISTA) aircraft and evaluated using a software rate limit (SWRL) with and without an RLPF on the pilot command path. A programmable heads-up-display (HUD) was used to generate a fighter tracking task. Flight test results showed the SWRL was useful in preventing departure and/or PIO. However, with low SWRL settings (

A Limited Flight Test Investigation of Pilot-Induced Oscillation Due to Elevator Rate Limiting (HAVE LIMITS).
A Limited Flight Test Investigation of Pilot-Induced Oscillation Due to Elevator Rate Limiting (HAVE LIMITS).

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Publisher:

Published: 1997

Total Pages: 0

ISBN-13:

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The report presents the results of a limited flight test investigation of pilot-induced oscillation (PIO) due to elevator rate limiting. The objective of this effort was to gather in-flight and ground-based simulation data on longitudinal PIO tendecies due to elevator rate limiting. Preliminary, ground-based simulation was conducted at the USAF Test Pilot School (TPS) from 1 March to 9 April 1997. Nine sorties, totaling 12.8 flight hours, were flown in the NT-33A aircraft. Additional ground-based simulation was conducted at the Flight Dynamics Directorate, Wright-Patterson AFB, Ohio, on 25 April 1997. The USAF TPS was the responsible test organization.

Results of Attempts to Prevent Departure And/or Pilot-Induced Oscillations (PIO) Due to Actuator Rate Limiting in Highly-Augmented Fighter Flight Control Systems (HAVE FILTER).
Results of Attempts to Prevent Departure And/or Pilot-Induced Oscillations (PIO) Due to Actuator Rate Limiting in Highly-Augmented Fighter Flight Control Systems (HAVE FILTER).

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Published: 1999

Total Pages: 0

ISBN-13:

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The objective of this effort was to evaluate the effects of software rate limiting the pilot command with and without a software pre-filter on a highly-augmented fighter aircraft flight control system. The software rate limiter and software pre-filter were designed to provide protection from departure and/or pilot-induced oscillation (PIO). In statically unstable aircraft stabilized with feedback, elevator/stabilator actuator rate limiting may lead to PIOs and/or departure during aggressive maneuvers. This project examined the use of a software rate limiter (SWRL) on the pilot command and compared the results with those for the unprotected airframe. Additionally, a nonlinear rate limiter pre-filter (RLPF) was used in conjunction with the SWRL. Previous attempts to suppress PIO and/or departure tendencies using similar technologies have encountered difficulty with noise-in-the-loop and out-of-trim bias development during filter operation. This project attempted to improve previous designs using a different algorithm for the RLPF. The SWRL was found to help prevent PIO and/or departure. The RLPF plus SWRL was generally found to be more helpful than the SWRL alone at preventing PIO and/or departure. However, handling qualities deficiencies arose when using low SWRL settings and worsened with low SWRL settings used in conjunction with the RLPF.