Ideal Lift Distributions and Flap Angles for Adaptive Wings

An approach is presented for determining the optimum flap angles and spanwise loading to suit a given flight condition. Multiple trailing-edge flaps along the span of an adaptive wing are set to either reduce drag in rectilinear flight conditions or to limit the wing bending moment at maneuvering conditions. For reducing drag, the flaps are adjusted to minimize induced drag, while simultaneously enabling the wing sections to operate within their respective low-drag ranges. For limiting wing bending moment, the flaps are used to relieve the loading near the wing tips. An important element of the approach is the decomposition of the flap angles into a distribution that can be used to control the spanwise loading for induced-drag control and a constant flap that can used for profile-drag control. The problem is linearized using the concept of basic and additional lift distributions, which enables the use of standard constrained-minimization formulations. The results for flap-angle distributions for different flight conditions are presented for a planar and a nonplanar wing. Postdesign analysis and aircraft-performance simulations are used to validate the optimum flap-angle distributions determined using the current approach.

[1]  Raymond F Anderson,et al.  Determination of the Characteristics of Tapered Wings , 1937 .

[2]  Robert Thomas Jones,et al.  The Spanwise Distribution of Lift for Minimum Induced Drag of Wings Having a Given Lift and a Given Bending Moment , 1950 .

[3]  Warren F. Phillips,et al.  Lifting-Line Analysis of Roll Control and Variable Twist , 2003 .

[4]  Alexander Bolonkin,et al.  Estimated Benefits of Variable-Geometry Wing Camber Control for Transport Aircraft , 1999 .

[5]  Egon Stanewsky,et al.  Aerodynamic benefits of adaptive wing technology , 2000 .

[6]  J. A. Blackwell.  Numerical method to calculate the induced drag or optimum loading for arbitrary non-planar aircraft , 1976 .

[7]  Ashok Gopalarathnam,et al.  Effect of Airfoil Characteristics on Aircraft Performance , 2002 .

[8]  Gregory W. Reich,et al.  Large-Area Aerodynamic Control for High-Altitude Long- Endurance Sensor Platforms , 2005 .

[9]  Mark D. Maughmer,et al.  THE DESIGN OF WINGLETS FOR HIGH-PERFORMANCE SAILPLANES , 2003 .

[10]  A. M. Kuethe,et al.  Foundations of aerodynamics: bases of aerodynamic design , 1986 .

[11]  Holger Hanselka,et al.  Design aspects of the adaptive wing — the elastic trailing edge and the local spoiler bump , 2000, The Aeronautical Journal (1968).

[12]  J. J. Spillman,et al.  The use of variable camber to reduce drag, weight and costs of transport aircraft , 1992, The Aeronautical Journal (1968).

[13]  Anna-Maria Rivas McGowan,et al.  The Aircraft Morphing Program , 1998 .

[14]  Ashok Gopalarathnam,et al.  Automated Cruise Flap for Airfoil Drag Reduction over a Large Lift Range , 2002 .

[15]  Ashok Gopalarathnam,et al.  Inverse Design of Adaptive Airfoils with Aircraft Performance Considerations , 2004 .

[16]  W. Pfenninger,et al.  Experiments on a Laminar Suction Airfoil of 17 Per Cent Thickness , 1949 .

[17]  Werner Pfenninger,et al.  Investigations on reductions of friction on wings, in particular by means of boundary layer suction , 1947 .

[18]  Max M Munk,et al.  The Minimum Induced Drag of Aerofoils , 1979 .

[19]  J P Fielding.  DESIGN INVESTIGATION OF VARIABLE - CAMBER FLAPS FOR HIGH-SUBSONIC AIRLINERS , 2000 .

[20]  M. Drela.  XFOIL: An Analysis and Design System for Low Reynolds Number Airfoils , 1989 .

[21]  D. M. Somers,et al.  Design and experimental results for a flapped natural-laminar-flow airfoil for general aviation applications , 1981 .

[22]  W. D. Beasley,et al.  Experimental Results for a Flapped Natural-laminar-flow Airfoil with High Lift/drag Ratio , 1984 .

[23]  I. H. Abbott,et al.  Theory of Wing Sections , 1959 .

[24]  S. V. Thornton,et al.  Reduction of structural loads using maneuver load control on the Advanced Fighter Technology Integration (AFTI)/F-111 mission adaptive wing , 1993 .