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Meeting	ACGS Committee Meeting 96 - Hilton Head - October 2005
Agenda Location	6 SUBCOMMITTEE D - DYNAMICS, COMPUTATIONS 6.4 Flight Control System Updates to Minimize Pilot-Induced Oscillations in a Large Transport Aircraft
Title	Flight Control System Updates to Minimize Pilot-Induced Oscillations in a Large Transport Aircraft
Presenter	Kamal Shweyk & Gary Weltz
Affiliation	Boeing
Available Downloads*	presentation
	Downloads are available to members who are logged in and either Active* or attended this meeting.
Abstract	This paper describes the overall approach that was adopted by the Boeing Flight Controls design team to address recent lateral Pilot-Induced Oscillation (PIO) incidents with the C-17A Globemaster III during Approach and Landing. The topics discussed include root cause analyses, design goals and criteria, proposed control law changes, flying qualities analyses, and validation of the design changes. The primary focus of the paper is the revised control laws intended to mitigate the lateral PIO tendencies and the subsequent piloted simulation evaluations. A key feature of the proposed control law design change is to reduce roll command gain and authority by default. Other significant improvements include a more linear roll command gain stick shaping, increased roll rate feedback gains, the addition of roll command lead compensation, elimination of unnecessary command filtering, and increased software surface rate limits. Roll performance concerns resulting from the reduction in roll command gain and authority were mitigated by analysis to ensure that the time-to-bank requirements are always met. Additionally, full roll command authority is restored following all failures in which rolling performance has been severely compromised. Validation of the design changes entailed both off-line analyses and formal piloted simulation tests. The latter option was not exercised until the former produced acceptable results against applicable flying qualities criteria and guidelines. The piloted evaluations involved a wide variety of flight maneuvers that described both gross acquisition tasks and fine tracking tasks. It will be shown that the simulator results supported the off-line analyses, thus further validating the design changes.