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| Meeting | ACGS Committee Meeting 97 - Tahoe - March 2006 | | Agenda Location | 4 GENERAL COMMITTEE TECHNICAL SESSION
4.1 Government Agencies Summary Reports
4.1.2 U.S. Navy
4.1.2.1 NAWCAD S&T | | Title | NAWCAD S&T | | Presenter | Marc Steinberg | | Available Downloads* | presentation
video1
video2 | | *Downloads are available to members who are logged in and either Active or attended this meeting. | | Abstract | Retrofit Reconfigurable Control Flight Test on an F/A-18C. The retrofit reconfigurable control system works by modifying the pilot inputs (I.e., stick and rudder commands) to make the aircraft behave as expected (as close to normal as possible) even in the face of disturbance and axis coupling that can result from actuator failure or aircraft damage. There are three major parts to the system: 1) a reference model of desired aircraft response, 2) a system model of how the aircraft is actually responding, 3) an optimal controller that adjusts gains on-line to make the actual response track the desired response. The system has been through non-real-time batch simulation testing, software only piloted simulation, hardware-in-the-loop simulation testing, and a flight test program. Flight testing has been restricted to a low dynamic pressure part of the envelope at altitude to ease flight clearance requirements related to software safety. For the software only simulation, the retrofit system modified both the pilot stick and rudder commands. Since the flight test hardware has the limited computational resources of a 1750A processor, an examination of using only pilot stick modifications was undertaken. It was concluded that a meaningful demonstration could be made using a stick-only architecture. The failures under consideration were locking a surface at an offset from trim. The ranges were 30 deg. for the aileron and 6 deg. for the stab. The test maneuvers were doublets, attitude captures, and tracking. The F-18 A/C configuration was clean except for a center-line tank. Both cruise and powered approach points were examined. Flight test data showed the aircraft behavior for the 30 deg. aileron failure for the case without retrofit control. As the failure comes in, it takes a certain amount pilot effort to maintain wings level flight. It also takes the pilot a considerable amount of time to trim the aircraft the best that he can. Once trimmed, the pilot initiates some pitch doublets. A lot of coupling in yaw and roll can be seen and this is accompanied by a lot of activity in the pilot inputs to compensate. A second set of flight test data was shown for the 30 deg. aileron failure with retrofit control. Once trimmed, the pilot initiates some pitch doublets. Some coupling in yaw and minor coupling in roll is still present, but much reduced from the retrofit off case. The retrofit inputs can be seen to be actively compensating for the aileron failure. The improved response when using the retrofit controller translates into improved HQRs. Also, the improvement is on par with that which was seen in the HILS testing. However, this was a limited flight test only. |
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