An In-Flight Interaction of the X-29A Canard and Flight Control System
Kehoe, Michael W. and Laurie, Edward J. and Bjarke, Lisa J. (1990) An In-Flight Interaction of the X-29A Canard and Flight Control System. Technical Report NASA TM-101718, Research Engineering, NASA Dryden Flight Research Center.
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Abstract
Many of today's high performance airplanes use high gain, digital flight control systems. These systems are liable to couple with the aircraft's structural dynamics and aerodynamics to cause an aeroservoelastic interaction. These interactions can be stable or unstable depending upon damping and phase relationships within the system. This paper presents the details of an aeroservoelastic interaction experienced in flight by the X-29A forward-swept wing airplane. A 26.5-Hz canard pitch mode response was aliased by the digital sampling rate in the canard position feedback loop of the flight control system, resulting in a 13.5-Hz signal being commanded to the longitudinal control surfaces. The amplitude of this commanded signal increased as the wear of the canard seals increased, as the feedback path gains were increased, and as the canard aerodynamic loading decreased. The resultant control surface deflections were of sufficient amplitude to excite the structure. The flight data presented shows the effect of each component (structural dynamics, aerodynamics, and flight control system) for this aeroservoelastic interaction.
| EPrint Type: | NASA Technical Memorandum |
|---|---|
| Keywords: | Aerodynamic loads, Aeroservoelasticity, Flight control structure interaction, Flight controls, Forward-swept wing, Structural dynamics, X-29A aircraft |
| Subjects: | (01 - 09) Aeronautics: (05) Aircraft Design, Testing And Performance Aircraft/Project: X-29 |
| ID Code: | 1094 |
| Deposited On: | 11 September 2006 |
| Additional Information: | 21 pages. Presented at the AIAA Dynamics Specialists Meeting, Long Beach, California, April 5–6, 1990. |
