Title page for ETD etd-12122003-133051

Type of Document Master's Thesis
Author Leonard, John
URN etd-12122003-133051
Title Investigation of Lateral-Directional Coupling in the Longitudinal Responses of a Transfer Function Simulation Model
Degree Master of Science
Department Aerospace and Ocean Engineering
Advisory Committee
Advisor Name Title
Durham, Wayne C. Committee Chair
Hovakimyan, Naira Committee Member
Lutze, Frederick H. Jr. Committee Member
Woolsey, Craig A. Committee Member
  • transfer functions
  • longitudinal responses
  • mode coupling
  • flight simulation
Date of Defense 2003-12-05
Availability unrestricted
The linear variable stability Transfer Function Simulation Model (TFSM), inspired by the United States Air Force's NF-16D Variable stability In-flight Simulator Test Aircraft (VISTA) and created by Henrik Pettersson, can simulate any desired aircraft. The TFSM represents a non-linear aircraft model with its stability parameters - a collection of gain constants, time constants, damping ratios, and natural frequencies. Stability parameters for aircraft generally fall into two uncoupled modes: longitudinal and lateral-directional. Unfortunately, flight tests using the TFSM exhibited undesired lateral-directional coupling in the longitudinal responses.

An S-turn maneuver, formation flight test, and an uncontrolled simulation with an initial bank angle of 60 degrees were the foundation for the investigation to pinpoint the TFSM's errors. The flight tests and subsequent analysis showed that although this model is highly versatile, it has three fundamental problems. First, the original creation of the TFSM incorrectly assumed that the time rate of change for the pitch angle (in the local-horizontal reference frame) is equal to the body-axis pitch-rate for all flight conditions. Second, the TFSM's dynamics do not contain gravity terms. Third, the TFSM cannot generate the angular rates needed in a turn.

Integrating the aircraft's pitch, roll, and yaw angles with the equations of motion for aircraft fixed the first problem. Unfortunately, resolving this issue only intensified the second two problems. The results from this thesis show that the last two problems are part of the TFSM and cannot be fixed explicitly.

  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
  Leonard_Thesis.pdf 1.49 Mb 00:06:53 00:03:32 00:03:06 00:01:33 00:00:07

Browse All Available ETDs by ( Author | Department )

dla home
etds imagebase journals news ereserve special collections
virgnia tech home contact dla university libraries

If you have questions or technical problems, please Contact DLA.