Progress in tail rotor noise analysis

Helicopter tail rotor noise generated by interactions with the main rotor tip vortices and with the fuselage separation mean wake is investigated. The tail rotor blade-main rotor tip vortex interaction is modeled as an airfoil of infinite span cutting through a moving vortex. The present results are compared to the tail rotor loading and high speed thickness noise and are found to be significant. This noise mechanism is a function of the helicopter operating conditions and the location of the tail relative to the main rotor. Tail rotor self-generated noise due to turbulent vortex shedding from blunt trailing edges is also analyzed.