Fuselage Influence on the Airflow at the Propellers of a Multiengined Airplane in Yawed Flight

R P Harrington,Victor Zadikov

doi:10.2514/8.11132

R P Harrington, Victor Zadikov

https://doi.org/10.2514/8.11132

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The paper develops expressions for the aerodynamic interference of the fuselage of multiengined airplanes on the propellers for the general case of yawed flight. Such effects of the fuselage are considered as increased or decreased velocity components— one of which is parallel to the axis of rotation of the propeller; and the other, along a radius of the fuselage cross section in the plane of the propeller. The latter velocity component is later expressed as a tangential increment at any radius and position of the blade. The fore part of the fuselage is approximated by an ellipsoid of revolution. The disturbances attributed to the fuselage are considered as those due to an additional potential tha t satisfies the equation of continuity and the boundary conditions at the surface of the ellipsoid—i.e., tha t the normal velocity components at the surface vanish. The development is facilitated by the application of ellipsoidal harmonics. The coordinate system consists of confocal ellipsoids of revolution and hyperboloids of two sheets. The third coordinate is the angle of rotation about the major axis of the ellipsoid. The velocity components desired are found by differentiating the additional potential partially with respect to the line element in the desired direction. Values of the disturbing velocities expressed in terms of WQ, the resultant velocity of the airplane, are worked out for a special case of propeller location. The effect of these velocities on the angle of attack of a blade element at 75 per cent radius is depicted by curves for yawing angles between ±90° . When the propeller diameter is assumed to be 3b, where b is the maximum radius of the fuselage, and is located in a plane at 1.2b from the nose with its axis located 2.75b from the centerline of the fuselage, the angle-of-attack increments of the element amount to 2.6° at certain blade positions for a typical installation at zero yaw.

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