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Abstract
A novel technique for estimating the stability margins in near real time has been developed by the authors [1]. This paper shares the invaluable flight test experience gained in using it for flight envelope expansion of India’ s first digital fly-by-wire Light Combat Aircraft (LCA). Use of this technique has resulted in reducing the overall flight test effort and cost without compromising safety.
Using the technique, it was possible to estimate the stability margins on a desktop computer using real time telemetry data within approximately 60 seconds of completing the test. The flight test results for ‘Fixed’ (restricted flight envelope) and ‘Scheduled’ (full flight envelope) gain control laws, for manually generated pilot 3-2-1-1 inputs and pre-programmed 3-2-1-1 inputs generated using the onboard Flight Test Panel (FTP) are presented.
During the LCA flights, the stability margins were found to be satisfactory throughout the flight envelope. In order to establish that the same technique would work equally well when the stability margins are marginal, typical results were also generated using simulation data and are included in this paper. By artificially increasing the plant gain / delay in the simulation model it is shown that even if the stability margins are low, the same technique correctly estimates the relative stability.
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References
- Vijay V. Patel., Girish Deodhare. and Shyam Chetty., "Near Real Time Stability Margin Estimation from Piloted 3-2-1-1 Inputs", AIAA Aircraft Technology Integration and Operations (A TIO2002) Technical Forum, Los Angeles, CA, October 2002.
- Smith, T., "Ground and Flight Testing of Digital Flight Control Systems", Chapter 6, Flight Control Systems, Edited by Roger W. Pratt, Progress in Astronautics and Aeronautics, Vol.184, Paul Zarchan, Editor-in-Chief, 2000.
- Mark B. Tischler., "System Identification Methods for Aircraft Flight Control Development and Validation", Chapter 2, Advances in Aircraft Flight Control, Taylor and Francis, 1996.
- Peter G. Hamel. and Ravindra Jategaonkar., "Evolution of Flight Vehicle System Identification", Journal of Aircraft, Vol. 33, No.1, January-February 1996, pp. 9-28.
- Shyam Chetty., Girish Deodhare. and B. B. Misra, "Design, Development and Flight Testing of Control Laws for the Indian Light Combat Aircraft", AIAA Conference on Guidance, Navigation and Control, 2002.
- Alan V. Oppenheim. and Ronald W. Schafer., Digital Signal Processing, Prentice Hall, 1989.
- McRuer D. Ashkenas. and Graham, D., Aircraft Dynamics and Automatic Control, Princeton, New Jersy, 1973.
- Robert Clarke., John J. Burken., John T. Bosworth. and Jeffery E. Bauer., "X-29 Flight Control System: Lessons Learned", NASA Technical Memorandum 4598, June 1994.
- John T. Bosworth. and John J. Burken., "Tailored Excitation for Multivariable Stability-Margin Measurement Applied to the X-31A Nonlinear Simulation", NASA Technical Memorandum 113085, Au- gust 1997.
- Nanson, K.M. and Ramsay, R.B., "The Development and Use of inflight Analysis at BAE Warton", Advances in Flight Testing, AGARD-CP-593, December 1997.
References
Vijay V. Patel., Girish Deodhare. and Shyam Chetty., "Near Real Time Stability Margin Estimation from Piloted 3-2-1-1 Inputs", AIAA Aircraft Technology Integration and Operations (A TIO2002) Technical Forum, Los Angeles, CA, October 2002.
Smith, T., "Ground and Flight Testing of Digital Flight Control Systems", Chapter 6, Flight Control Systems, Edited by Roger W. Pratt, Progress in Astronautics and Aeronautics, Vol.184, Paul Zarchan, Editor-in-Chief, 2000.
Mark B. Tischler., "System Identification Methods for Aircraft Flight Control Development and Validation", Chapter 2, Advances in Aircraft Flight Control, Taylor and Francis, 1996.
Peter G. Hamel. and Ravindra Jategaonkar., "Evolution of Flight Vehicle System Identification", Journal of Aircraft, Vol. 33, No.1, January-February 1996, pp. 9-28.
Shyam Chetty., Girish Deodhare. and B. B. Misra, "Design, Development and Flight Testing of Control Laws for the Indian Light Combat Aircraft", AIAA Conference on Guidance, Navigation and Control, 2002.
Alan V. Oppenheim. and Ronald W. Schafer., Digital Signal Processing, Prentice Hall, 1989.
McRuer D. Ashkenas. and Graham, D., Aircraft Dynamics and Automatic Control, Princeton, New Jersy, 1973.
Robert Clarke., John J. Burken., John T. Bosworth. and Jeffery E. Bauer., "X-29 Flight Control System: Lessons Learned", NASA Technical Memorandum 4598, June 1994.
John T. Bosworth. and John J. Burken., "Tailored Excitation for Multivariable Stability-Margin Measurement Applied to the X-31A Nonlinear Simulation", NASA Technical Memorandum 113085, Au- gust 1997.
Nanson, K.M. and Ramsay, R.B., "The Development and Use of inflight Analysis at BAE Warton", Advances in Flight Testing, AGARD-CP-593, December 1997.