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  • Print publication year: 2013
  • Online publication date: May 2013

12 - Stall


To maintain low drag and high lift, the flow over an airfoil section must remain smooth and attached to the surface. This flow has a rapid acceleration around the nose of the airfoil to the point of maximum suction pressure, and then a slow deceleration along the remainder of the upper surface to the trailing edge. The deceleration must be gradual for the flow to remain attached to the surface. At a high enough angle-of-attack, stall occurs: the deceleration is too large for the boundary layer to support, and the flow separates from the airfoil surface. The maximum lift coefficient at stall is highly dependent on the Reynolds number, Mach number, and the airfoil shape. Figure 8.12 shows clmax values from 1.0 to 1.6 for various airfoils, corresponding to stall angles-of-attack of 10° to 16°. The unstalled airfoil has a low drag and a lift coefficient linear with angle-of-attack. The airfoil in stall at high angles-of-attack has high drag, a loss of lift, and an increased nose-down pitch moment caused by a rearward shift of the center of pressure. The aerodynamic flow field of an airfoil or wing in stall is complex, and for the rotary wing there are important three-dimensional and unsteady phenomena as well.

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Bailey, F.J. Jr., “A Simplified Theoretical Method of Determining the Characteristics of a Lifting Rotor in Forward Flight.” NACA Report 716, 1941.
Bousman, W.G.A Qualitative Examination of Dynamic Stall from Flight Test Data.” Journal of the American Helicopter Society, 43:4 (October 1998).
Bousman, W.G.Evaluation of Airfoil Dynamic Stall Characteristics for Maneuverability.” Journal of the American Helicopter Society, 46:4 (October 2001).
Carr, L.W., McAlister, K.W., and McCroskey, W.J.Analysis of the Development of Dynamic Stall Based on Oscillating Airfoil Experiments.” NASA TN D-8382, January 1977.
Floros, M.W., Gold, N.P., and Johnson, W.An Exploratory Aerodynamic Limits Test with Analytical Correlation.” American Helicopter Society 4th Decennial Specialist's Conference on Aeromechanics, San Francisco, CA, January 2004.
Fradenburgh, E.A.Aerodynamic Efficiency Potential of Rotary Wing Aircraft.” American Helicopter Society 16th Annual National Forum, Washington, DC, May 1960.
Gessow, A., and Myers, G.C. Jr., Aerodynamics of the Helicopter. New York: The Macmillan Company, 1952.
Gormont, R.E.A Mathematical Model of Unsteady Aerodynamics and Radial Flow for Application to Helicopter Rotors.” USAAVLABS TR 72-67, May 1973.
Green, R.B., Galbraith, R.A.M., and Niven, A.J.Measurements of the Dynamic Stall Vortex Convection Speed.” Seventeenth European Rotorcraft Forum, Berlin, Germany, September 1991.
Gustafson, F.B., and Gessow, A.Effect of Blade Stalling on the Efficiency of a Helicopter Rotor as Measured in Flight.” NACA TN 1250, April 1947.
Gustafson, F.B., and Myers, G.C. Jr., “Stalling of Helicopter Blades.” NACA Report 840, 1946.
Hafner, R.The Bristol 171 Helicopter.” The Journal of the Royal Aeronautical Society, 53:460 (April 1949).
Ham, N.D., and Garelick, M.S.Dynamic Stall Considerations in Helicopter Rotors.” Journal of the American Helicopter Society, 13:2 (April 1968).
Ham, N.D., and Young, M.I.Torsional Oscillation of Helicopter Blades due to Stall.” Journal of Aircraft, 3:3 (May-June 1966).
Harris, F.D.Rotary Wing Aerodynamics – Historical Perspective and Important Issues.” American Helicopter Society National Specialists' Meeting on Aerodynamics and Aeroacoustics, Arlington, TX, February 1987.
Harris, F.D., Tarzanin, F.J. Jr., and Fisher, R.K. Jr., “Rotor High Speed Performance, Theory vs. Test.” Journal of the American Helicopter Society, 15:3 (April 1970).
Johnson, W.Rotorcraft Aerodynamic Models for a Comprehensive Analysis.” American Helicopter Society 54th Annual Forum, Washington, DC, May 1998.
Leishman, J.G., and Beddoes, T.S.A Generalised Model for Airfoil Unsteady Aerodynamic Behaviour and Dynamic Stall Using the Indicial Method.” American Helicopter Society 42nd Annual Forum, Washington DC, June 1986.
Leishman, J.G., and Beddoes, T.S.A Semi-Empirical Model for Dynamic Stall.” Journal of the American Helicopter Society, 34:3 (July 1989).
Leishman, J.G., and Crouse, G.L. Jr., “State-Space Model for Unsteady Airfoil Behavior and Dynamic Stall.” AIAA Paper No. 89-1319, April 1989.
McCloud, J.L. III, and McCullough, G.B.Wind-Tunnel Tests of a Full-Scale Helicopter Rotor with Symmetrical and with Cambered Blade Sections at Advance Ratios from 0.3 to 0.4.” NACA TN 4367, September 1958.
McCormick, B.W. Jr., Aerodynamics of V/STOL Flight. New York: Academic Press, Inc., 1967.
McCroskey, W.J.The Phenomenon of Dynamic Stall.” NASA TM 81264, March 1981.
McCroskey, W.J., and Fisher, R.K. Jr., “Detailed Aerodynamic Measurements on a Model Rotor in the Blade Stall Regime.” Journal of the American Helicopter Society, 17:1 (January 1972).
McCroskey, W.J., and Pucci, S.L.Viscous-Inviscid Interaction on Oscillating Airfoils in Subsonic Flow.” AIAA Journal, 20:2 (February 1982).
McHugh, F.J.What Are the Lift and Propulsive Force Limits of High Speed for the Conventional Rotor?” American Helicopter Society 34th Annual National Forum, Washington, DC, May 1978.
Martin, J.M., Empey, R.W., McCroskey, W.J., and Caradonna, F.X.An Experimental Analysis of Dynamic Stall on an Oscillating Airfoil.” Journal of the American Helicopter Society, 19:1 (January 1974).
Norman, T.R., Shinoda, P., Peterson, R.L., and Datta, A.Full-Scale Wind Tunnel Test of the UH-60A Airloads Rotor.” American Helicopter Society 67th Annual Forum, Virginia Beach, VA, May 2011.
Peters, D.A.Toward a Unified Lift Model for Use in Rotor Blade Stability Analyses.” Journal of the American Helicopter Society, 30:3 (July 1985).
Petot, D.Progress in the Semi-Empirical Prediction of the Aerodynamic Forces due to Large Amplitude Oscillations of an Airfoil in Attached or Separated Flow.” Ninth European Rotorcraft Forum, Stresa, Italy, September 1983.
Petot, D.Dynamic Stall Modeling of the NACA 0012 Profile.” La Recherche Aerospatiale, 1984:6 (1984).
Petot, D.Differential Equation Modeling of Dynamic Stall.” La Recherche Aerospatiale, 1989:5 (1989), corrections dated October 1990.
Petot, D.An Investigation of Stall on a 4.2m Diameter Experimental Rotor.” Seventh International Workshop on Dynamics and Aeroelastic Modeling of Rotorcraft, St. Louis, MO, October 1997.
Sikorsky, I.A.Aerodynamic Parameters Selection in Helicopter Design.” Journal of the American Helicopter Society, 5:1 (January 1960).
Stepniewski, W.Z.Introduction to Helicopter Aerodynamics. Morton, PA: Rotorcraft Publishing Committee, 1955 (first edition 1950).
Tanner, W.H.Charts for Estimating Rotary Wing Performance in Hover and at High Forward Speeds.” NASA CR 114, November 1964.
Tarzanin, F.J. Jr., “Prediction of Control Loads Due to Blade Stall.” Journal of the American Helicopter Society, 17:2 (April 1972).
Yeo, H.Calculation of Rotor Performance and Loads Under Stalled Conditions.” American Helicopter Society 59th Annual Forum, Phoenix, AZ, May 2003.