CEAS Aeronautical Journal

, Volume 5, Issue 1, pp 1–11 | Cite as

A finite-state aeroelastic model for rotorcraft–pilot coupling analysis

  • Jacopo Serafini
  • Marco Molica Colella
  • Massimo Gennaretti
Original Paper


Rotorcraft–pilot coupling (RPC) denotes interplay between pilot and helicopter (or tiltrotor) that may give rise to adverse phenomena. These are usually divided into two main classes: pilot-induced oscillations driven by flight dynamics and behavioural processes, and pilot-assisted oscillations (PAO) caused by unintentional actions of pilot on controls, owing to involuntary reaction to seat vibrations. The aim of this paper is the development of mathematical helicopter models suited for analysis of RPC phenomena. In addition to rigid-body dynamics, RPCs (especially PAO) are also related to fuselage structural dynamics and servoelasticity; however, a crucial role is played by main rotor aeroelasticity. In this work, the aeroelastic behaviour of the main rotor is simulated through a novel finite-state modeling that may conveniently be applied for rotorcraft stability and response analyses, as well as for control synthesis applications. Numerical results, first are focused on the validation of the proposed novel main rotor model, and then present applications of the developed comprehensive rotorcraft model for the RPC analysis of a Bo-105-type helicopter. Specifically, these deal with the stability of vertical bouncing, which is a PAO phenomenon caused by coupling of vertical pilot seat acceleration with collective control stick, driven by inadvertent pilot actions. Further, considering quasi-steady, airfoil theory with wake inflow correction and three-dimensional, potential-flow, boundary element method approaches, the sensitivity of PAO simulations to different aerodynamic load models applied within the main rotor aeroelastic operator is also investigated.


Rotor aeroelasticity State-space modelling Rotorcraft–pilot coupling 



The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007–2013) under grant agreement No. 266073.


  1. 1.
    Pavel, M., Yilmaz, D.: Background, definition and classification of a/rpc. Tech. Rep. Deliverable D1.1, EU funded project ARISTOTEL (GA no. 266073) (2010)Google Scholar
  2. 2.
    Barry Walden, R.: A retrospective survey of pilot–structural coupling instabilities in naval rotorcraft. In: 63rd Annual Forum of the American Helicopter Society (2007)Google Scholar
  3. 3.
    Parham, T.J., Popelka, D., Miller, D., Froebel, A.: V-22 pilot-in the-loop aeroelastic stability analysis. In: 47th Annual Forum of the American Helicopter Society (1991)Google Scholar
  4. 4.
    Pavel, M., Malecki, J., Dang Vu, B., Masarati, P.M., Jump, M., Jones, M., Smaili, H., Ionita, A., Zaicek, L.: Present and future trends in rotorcraft pilot couplings (rpcs)—a retrospective survey of recent research activities within the European project ARISTOTEL. In: 37th European Rotorcraft Forum 2011 (ERF 2011), pp. 266–284. Curran Associates, Inc. (2012)Google Scholar
  5. 5.
    Serafini, J., Gennaretti, M., Masarati, P., Quaranta, G., Dieterich, O.: Aeroelastic and biodynamic modelling for stability analysis of rotorcraft–pilot coupling phenomena. In: 34th European Rotorcraft Forum 2008 (ERF34), pp. 1572–1607. Curran Associates, Inc. (2011)Google Scholar
  6. 6.
    Masarati, P., Quaranta, G., Gennaretti, M., Serafini, J.: An investigation of aeroelastic rotorcraft–pilot interaction. In: 37th European Rotorcraft Forum 2011 (ERF 2011), pp. 251–265. Curran Associates, Inc. (2012)Google Scholar
  7. 7.
    Gennaretti, M., Muro, D.: Multiblade reduced-order aerodynamics for state-space aeroelastic modeling of rotors. J. Aircr. 49(2), 495–502 (2012)CrossRefGoogle Scholar
  8. 8.
    Hodges, D.H., Dowell, E.H.: Nonlinear equation for the elastic bending and torsion of twisted nonuniform rotor blades. Tech. Rep. TN D-7818, NASA (1974)Google Scholar
  9. 9.
    Gennaretti, M., Molica Colella, M., Bernardini, G.: Prediction of tiltrotor vibratory loads with inclusion of wing–proprotor aerodynamic interaction. J. Aircr. 47(1), 71–79 (2010)CrossRefGoogle Scholar
  10. 10.
    Gennaretti, M., Bernardini, G.: Novel boundary integral formulation for blade–vortex interaction aerodynamics of helicopter rotors. AIAA J. 45(6), 1169–1176 (2007)CrossRefGoogle Scholar
  11. 11.
    Theodorsen, T.: General theory of aerodynamic instability and the mechanism of flutter. Tech. Rep. Report 496, NACA (1935)Google Scholar
  12. 12.
    Mayo, J.: The involuntary participation of a human pilot in a helicopter collective control loop. In: 15th European Rotorcraft Forum: September 12–15, 1989, Amsterdam, The Netherlands. Assoc. Industrie Aerospaziali (1989)Google Scholar
  13. 13.
    Gennaretti, M., Bernardini, G.: Aeroacousto-elastic modeling for response analysis of helicopter rotors. In: Buttazzo, G., Frediani, A. (eds.): Variational Analysis and Aerospace Engineering: Mathematical Challenges for Aerospace Design, pp. 7–50. Springer, Berlin (2012)Google Scholar
  14. 14.
    Bernardini, G., Serafini, J., Ianniello, S., Gennaretti, M.: Assessment of computational models for the effect of aeroelasticity on bvi noise prediction. Int. J. Aeroacoustics 6(3), 199–222 (2007)CrossRefGoogle Scholar
  15. 15.
    Gennaretti, M., Muro, D.: A multiblade aerodynamic reduced-order model for aeroelastic analysis of helicopter rotors in forward flight. In: 36th European Rotorcraft Forum 2010 (ERF 2010) (2010)Google Scholar
  16. 16.
    Muro, G., Gennaretti, M.: Stability analysis of helicopter rotors in forward flight via state-space aeroelastic modeling and correlation with experimental results. In: 37th European Rotorcraft Forum 2011 (ERF 2011), pp. 64–71. Curran Associates, Inc. (2012)Google Scholar
  17. 17.
    Quaranta, G., Tamer, A., Muscarello, V., Masarati, P., Gennaretti, M., Serafini, J., Molica Colella, M.: Rotorcraft aeroelastic stability using robust analysis. CEAS Aeronautical J. (2013, in press)Google Scholar
  18. 18.
    Karpel, M.: Design for the active flutter suppression and gust alleviation using state-space aeroelastic modeling. J Aircr. 19(3), 221–227 (1982)CrossRefGoogle Scholar
  19. 19.
    Gennaretti, M., Greco, L.: A time-dependent coefficient reduced-order model for unsteady aerodynamics of proprotors. J. Aircr. 42(1), 138–147 (1982)Google Scholar
  20. 20.
    Padfield, G.: Helicopter Flight Dynamics. Blackwell Science, Oxford (1996)Google Scholar
  21. 21.
    Morino, L., Mastroddi, F., De Troia, R., Ghiringhelli, G.L., Mantegazza, P.: Matrix fraction approach for finite-state aerodynamic modeling. AIAA J. 33(4), 703–711 (1995)Google Scholar

Copyright information

© Deutsches Zentrum für Luft- und Raumfahrt e.V. 2013

Authors and Affiliations

  • Jacopo Serafini
    • 1
  • Marco Molica Colella
    • 1
  • Massimo Gennaretti
    • 1
  1. 1.Department of EngineeringUniversity Roma TreRomeItaly

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