Estimation of fly-by-wire emergency servo-control of regional aircraft with account for nonlinear specifics of control surfaces dynamics

Aeronautical and Space-Rocket Engineering


DOI: 10.34759/vst-2022-1-211-225

Аuthors

Terekhov R. I.

Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia

e-mail: Roman.Terekhov@tsagi.ru

Abstract

The author proposes an innovative option of emergency fly-by-wire servo-control to preserve controllability at both hydraulic systems failure for a prospective regional aircraft with fly-by-wire control system and two hydraulic systems. Two electro-hydraulic servo-actuators (EHSA), fed from the two independent hydraulic systems, and servotab with electromechanical actuator (EMA) are being installed on each main control surface. With both hydraulic systems failure, all EHSAs enter the passive mode (damping mode), and switching to servotabs emergency control occurs. The servotab deflection produces a hinge moment, which in its turn deflects the control surface. The aircraft handling qualities in the servo-control mode should ensure the capability of the safe flight termination.

Mathematical model of the control surface rotation under the impact of the external hinge moment, originating while the servotab control, was developed for computational and test-bench studies with account for the specifics caused by friction and damping effects from the electro-hydraulic servo-actuators operating in passive mode. The damping force value significantly affects the aircraft handling qualities in servotab control mode.

The results of numerical studies revealed that in order to meet the AMC CS-25 25.671(c) requirements for manoeuver capabilities after failures and the MIL-STD-1797 recommendations for maximum allowable phase lag between control stick pilot input and control surface response, the servotab control laws should contain speed-up pre-filters on pilot control signals, pitch rate feedback (elevator servotab control law), roll and yaw rates feedbacks (rudder servotab control law). The emergency servotab control algorithms parameters selecting, ensuring the set requirements meeting at various values of the EHSA damping coefficient, was performed.

To confirm the possibility of the safe flight termination with the selected servotab emergency control law parameters, the test-bench tests on the flight simulator with participation of test pilots were conducted.

The approach and landing tasks with glideslope offset correction and with crosswind Wz = 5 m/s were under study. According to the pilots’ opinions, the aircraft handling qualities in servotab control mode correspond to the Cooper-Harper rating PR=4.5...5. Slight PIO tendency noted mostly in roll channel corresponds to the PIOR=3...3.5. The obtained pilot ratings confirm the correctness of the emergency servotab control algorithm parameters selection and the possibility of the safe flight termination in this mode.

Keywords:

servotab, hinge moment, friction modelling, actuator damping coefficient, control laws, prefilter, pitch damper

References

  1. Ermakov S.A., Karev V.I., Konstantinov S.V., Obolensky Y.G., Selivanov A.M., Sukhorukov R.V. Fly-by-wire control systems and servo actuators design and development. Aerospace MAI Journal, 2013, vol. 20, no 2, pp. 161-171.

  2. Moir I., Seabridge A. Aircraft Systems: Mechanical, electrical and avionics subsystems integration. Third Edition, John Wiley & Sons, Ltd., England, 2008, 504 p.

  3. Terekhov R.I., Shelyukhin Yu.F. Materialy XXIX Nauchno-tekhnicheskoi konferensii po aerodinamike, Мoscow, TsAGI, 2018, p. 183.

  4. Mikeladze V.G., Titov V.M. Osnovnye geometricheskiye i aerodinamicheskiye kharakteristiki samoletov i raket: Spravochnik (Basic geometric and aerodynamic characteristics of aircraft and rockets: guide), Moscow, Mashinostroenie, 1982, 149 p.

  5. Eger S.M., Matveenko A.M., Shatalov I.A. Osnovy aviatsionnoi tekhniki (Fundanentals of aeronautical engineering), Moscow, Mashinostroenie, 2003, 720 p.

  6. MD-88/90 Operations Manual Vol. 2, Delta Air Lines, Inc., USA, 2014, 744 p.

  7. Alyoshin B.S., Bazhenov S.G., Didenko Yu.I., Shelyukhin Yu.F. Sistemy disnantsionnogo upravleniya magistral’nykh samolyotov (Fly-by-wire control systems of airliners), Moscow, Nauka, 2013, 292 p.

  8. Bilyaletdinova L.R., Steblinkin A.I. Mathematical modeling of electromechanical steering gear with ball-screw actuator with account for nonlinearities of “dry friction” and “backlash” types. Aerospace MAI Journal, 2017, vol. 24, no. 3, pp. 95-108.

  9. Obolenskii Yu.G., Ermakov S.A., Sukhorukov R.V. Vvedenie v proektirovanie sistem aviatsionnykh rulevykh privodov (Introduction to aeronautical actuator systems design), Moscow, Izdatel’stvo GUP g. Moskvy “Okruzhnaya gazeta YuZAO”, 2011, 344 p.

  10. Aviatsionnye pravila. Chast’ 25. Normy letnoi godnosti samoletov transportnoi kategorii (Aviation Rules. Part 25. Norms of airworthiness of transport category aircraft). Interstate Aviation Committee, Moscow, Aviaizdat, 2015, 290 p.

  11. Certification Specifications and Acceptable Means of Compliance for Large Aeroplanes CS-25. Amendment 24. European Aviation Safety Agency (EASA), 2020. URL: https://www.easa.europa.eu/downloads/108354/en

  12. Advisory Material Joint. AC/AMJ 25.671 Control Systems General. Draft. U.S. Department of Transportation, Federal Aviation Administration, USA, 2001, 44 p.

  13. Terekhov R.I. Trudy MAI, 2017, no. 96, available at: http://trudymai.ru/eng/published.php?ID=85785

  14. Flying Qualities of Piloted Aircraft. MIL-STD-1797A Notice 3. Department of Defence Interface Standard, 2004, 722 p.

  15. Langton R. Stability and Control of Aircraft Systems. Introduction to Classical Feedback Control. John Wiley & Sons, Ltd., England, 2006, 238 p.

  16. Mbihi J. Analog Automation and Digital Feedback Control Techniques. ISTE Ltd., UK, 2018, 238 p.

  17. Byushgens G.S. Aerodinamika i dinamika polyota magistral’nykh samolyotov (Aerodynamics and flight dynamics of airliners), Moscow, Beijing, TsAGI publish office, PRC aero-publishing, 1995, 772 p.

  18. Flight Control Design – Best Practices. RTO Technical Report 29. NATO, France, 2000, 214 p.

  19. Cooper G.E., Harper R.P. The Use of Pilot Rating in the Evaluation of Aircraft Handling Qualities. NASA TN D-5153, 1969, 52 p.

  20. Weingarten N.C., Chalk C.R. In-Flight Investigation of Large Airplane Flying Qualities for Approach and Landing. AFWAL-TR-81-3118, 1981, 467 p.

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