Masters Theses

Date of Award

5-1994

Degree Type

Thesis

Degree Name

Master of Science

Major

Aviation Systems

Major Professor

Ralph Kimberlin

Committee Members

Paluden, Bob Richards

Abstract

This research involved the analytical development of a modification to the flight control system (FCS) of the Grumman/Navy F-14 Tomcat to reduce excessive sideslip generated during supersonic rolling maneuvers at normal accelerations greater than one g. The airplane currently has a flight manual limitation prohibiting lateral stick inputs greater than one-half stick deflection under these conditions to avoid exceeding the maximum recommended sideslip of 10 degrees.

A three degree-of-freedom, linear aerodynamic model was utilized for the FCS modification development with data reduction and analysis conducted with the MATLAB and SIMULINK computer programs. Analysis of the modification and stability of the aircraft was conducted using classical root locus techniques and time domain analysis.

Two design goals for this project were to use the maximum amount of existing aircraft hardware and to keep the control system design relatively simple to facilitate its incorporation into the currently available, off-the-shelf flight control computer (FCC). This could demonstrate the potential for utilizing modern control system design techniques to improve the flying qualities of existing aircraft and the potential for successful incorporation into the airframe with minimal cost.

No attempt has been made to correct this deficiency in the airplane's flying qualities. An effort is currently underway at Naval Air Warfare Center, Aircraft Division, NAS Patuxent River, MD and Grumman Corporation to develop a digital flight control system for the F-14, replacing the current analog system. The digital control laws will incorporate new functionality at subsonic Mach numbers to improve high angle of attack as well as takeoff and landing configuration flying qualities. The modification developed through this research could be incorporated in a follow-on version of this new system. Since the development of the digital FCS is not complete as of this writing, this modification was developed for the essentially identical analog system.

This research would be the first, analytical step in eliminating the flight manual restriction. A man-in-the-loop simulation, followed by flight tests would be required to fully verify the design's utility for incorporation into the operational airplane. The analysis and conclusions are the author's and not the US government's or the Naval Air Warfare Center's.

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