Limited Flight Investigation Of Strakes Mounted On A Helicopter Tail Boom

A limited flight investigation utilizing an OH-58A helicopter was conducted to determine the effect of several tail-boom strake configurations on yaw control during sideward flight. The purpose. was to determine if the strakes could alter the boom side force in a direction to increase the directional control margin in right sideward flight and to reduce the unsteady effects on the aircraft caused when the tail rotor is operated in the vortex-ring state during left sideward flight. Earlier wind-tunnel results have indicated that flow over a tail boom, induced primarily by the main rotor wake and sideward flight, result in high side forces on the boom and that a strake placed on the boom can reduce and, in some cases, reverse the direction of these loads. Flight-test results cbnfirmed that the boom strakes alter the aerodynamic loading on the boom with an improved pedal control margin and reduce tail rotor thrust required in right and left sideward flight. Strakes aggravated the unsteadiness of the basic air craft in left sideward flight.