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).

Author:

Publisher:

Published: 1997

Total Pages: 157

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.

Limited Investigation of the Effects of Elevator Rate Limiting and Stick Dynamics on Longitudinal Pilot Induced Oscillations (HAVE GRIP).
Limited Investigation of the Effects of Elevator Rate Limiting and Stick Dynamics on Longitudinal Pilot Induced Oscillations (HAVE GRIP).

Author:

Publisher:

Published: 1996

Total Pages: 0

ISBN-13:

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This report presents the results of the HAVE GRIP flight test program. This program performed a limited investigation of the effects of stick dynamics and elevator rate limiting on longitudinal pilot induced oscillations (PIOs) and was performed as a Test Management Project as part of the Test Pilot School curriculum. The theoretical research behind this flight test was performed as part of an Air Force Institute of Technology thesis under the sponsorship of Wright Laboratory's Flight Control Division. The research and flight testing was sponsored by the Flight Control Division of Wright Laboratory. The first phase of this program investigated how elevator rate limiting affected the susceptibility to PIOs during offset landing tasks. The second phase investigated how variations in stick spring constant and natural frequency affected the PIO susceptibility of the system at a given elevator rate limit. The third phase investigated the combined effects of changing elevator rate limits with variations in stick spring constant and natural frequency.

The Effects of Elevator Rate Limiting and Stick Dynamics on Longitudinal Pilot-Induced Oscillations
The Effects of Elevator Rate Limiting and Stick Dynamics on Longitudinal Pilot-Induced Oscillations

Author: Patrick J. Peters

Publisher:

Published: 1997-03-01

Total Pages: 147

ISBN-13: 9781423567370

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This report presents the results of an investigation into the effects of elevator rate limiting and stick dynamics on longitudinal pilot-induced oscillations (PIO). A simulation study was conducted to prepare for the flight test, but also to gain insight into the effects of rate limiting and stick dynamics. Due to the non-numerical nature of the simulation results, a flexible three-phase flight test plan was developed, first varying the rate limits, then varying the stick dynamics, and finally flying a matrix determined in the first two phases. There were three major conclusions. First, the offset landing task flown was insufficient to consistently uncover handling qualities deficiencies of the aircraft configuration flown. Second, rate limiting did not necessarily cause PIOs. At very low rate limits the problem was lack of pitch response, not PIO. Any oscillations were very low frequency and small in amplitude. Third, for this configuration and task, variations in stick spring constant and natural frequency had negligible effect on the performance of the system with respect to assigned PIO and Cooper-Harper ratings. These conclusions are specific to this system and may not apply to all aircraft, especially aircraft where PIO tendencies are driven by much higher rate limits.

Application of Sliding Mode Methods to the Design of Reconfigurable Flight Control Systems
Application of Sliding Mode Methods to the Design of Reconfigurable Flight Control Systems

Author: Scott R. Wells

Publisher:

Published: 2002

Total Pages: 624

ISBN-13:

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Observer-based sliding mode control is investigated for application to aircraft reconfigurable flight control. An overview of reconfigurable flight control is given, including a review of the current state-of-the-art within the subdisciplines of fault detection parameter identification, adaptive control schemes, and dynamic control allocation. Of the adaptive control methods reviewed, sliding mode control (SMC) appears promising due its property of invariance to matched uncertainty. An overview of SMC is given and its properties are demonstrated. Sliding mode methods, however, are difficult to implement because unmodeled parasitic dynamics cause immediate and severe instability. This presents a challenge for all practical applications with limited bandwidth actuators. One method to deal with parasitic dynamics is the use of an asymptotic observer. Observer-based SMC is investigated, and a method for selecting observer gains is offered. An additional method for shaping the feedback loop using a filter is also developed. It is shown that this SMC prefilter is equivalent to a form of model reference hedging. A complete design procedure is given which takes advantage of the sliding mode boundary layer to recast the SMC as a linear control law. Frequency domain loop shaping is then used to design the sliding manifold. Finally, three aircraft applications are demonstrated. An F-18/HARV is used to demonstrate SISO and MIMO designs. The third application is a linear six degree-of-freedom advanced tailless fighter model. The observer-based SMC is seen to provide excellent tracking with superior robustness to parameter changes and actuator failures.

Aviation Safety and Pilot Control
Aviation Safety and Pilot Control

Author: National Research Council

Publisher: National Academies Press

Published: 1997-03-28

Total Pages: 221

ISBN-13: 0309056888

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Adverse aircraft-pilot coupling (APC) events include a broad set of undesirable and sometimes hazardous phenomena that originate in anomalous interactions between pilots and aircraft. As civil and military aircraft technologies advance, interactions between pilots and aircraft are becoming more complex. Recent accidents and other incidents have been attributed to adverse APC in military aircraft. In addition, APC has been implicated in some civilian incidents. This book evaluates the current state of knowledge about adverse APC and processes that may be used to eliminate it from military and commercial aircraft. It was written for technical, government, and administrative decisionmakers and their technical and administrative support staffs; key technical managers in the aircraft manufacturing and operational industries; stability and control engineers; aircraft flight control system designers; research specialists in flight control, flying qualities, human factors; and technically knowledgeable lay readers.