Propeller-Rotor Aerodynamic Interaction in Helicopter Air-to-Air Refueling: an Analytical Solution for Rotor Trim

Abstract

During helicopter air-to-air refueling the rotor of the helicopter might enter the slipstream of the tanker aircraft's propeller. Based on blade element momentum theory, the impact of this jet on rotor blade aerodynamics is formulated. Rotor controls required to re-trim are solved analytically for the first time. The collective and cyclic controls needed for disturbance rejection are computed for a typical air-to-air refueling scenario. A propeller wake affecting the retreating side of the rotor requires much more pilot controls to retrim than an impingement on the advancing side. Variations of rotor angle of attack, propeller radius, and propeller thrust are performed.