Airfoil for controlling refueling boom

In a refueling boom having a longitudinal axis and mounted to an aircraft, a ruddevator assembly to act on flow of air over the ruddevator assembly to control movement and position of the boom, said ruddevator assembly comprising:

• a pair of ruddevators mounted to said boom at a dihedral angle to create both vertical and lateral lift components, each of said ruddevators having a spanwise axis and a chordwise axis, each ruddevator being mounted for rotation about an axis generally aligned with its spanwise axis, each ruddevator comprising:
• a. an outboard ruddevator section having an airfoil configuration with a leading edge shaped to cause attached flow over the outboard ruddevator section to create a lifting force caused by airflow over said outboard ruddevator section,
• b. an inboard ruddevator section having an airfoil configuration to create a lifting force caused by airflow over said inboard ruddevator section,
• c. said inboard ruddevator section having a forwardly extending strake-like member mounted to the forward end of the inboard ruddevator section,
• d. said strake-like member having a relatively sharp leading edge of a sufficiently small cross sectional radius to create detached flow of the air flow over said sharp leading edge, said sharp leading edge having three portions, namely,
• 1. a forward edge portion positioned generally transverse to the flow of air thereover,
• 2. an outboard lateral edge portion extending from the forward edge portion to the leading edge of the outboard ruddevator section at a sweep angle sufficient to create vortex flow of air passing over said outboard lateral edge portion,
• 3. an inboard lateral edge portion extending from the forward edge portion rearwardly along the inside edge of the ruddevator, the angular position of the inboard lateral edge portion being such that with the refueling boom extending at a downward angle from its associated aircraft so as to be positioned at an angle to the airstream, and with each ruddevator being positioned at an angle of attach such that the chordwise axis of each ruddevator is slanted with respect to a plane containing the lengthwise axis of the boom, the inboard lateral edge portion of the strake-like member extends into the airstream at a sweep angle sufficient to create vortex flow of air passing over said inboard lateral edge portion,
• whereby said ruddevators are able to create relatively high lift forces at relatively high angles of attack and under conditions of yaw of the boom where the sweep angles of the ruddevators are subject to variation.