Flowfield Effects on the Flight Dynamics and Control Response of Rotorcraft Operating in Close Proximity

Abstract

Requirements in future rotorcraft operations will likely place several aircraft in close-proximity to one another. Flowfield interference impacts on a secondary rotorcraft operating in the wake of a primary helicopter are investigated. Of primary concern is the degradation in the flight dynamics and control performance of the secondary helicopter. A free-vortex based wake is used to trim a primary helicopter and generate a flowfield. The secondary helicopter uses a finite-state inflow model, with one way coupling to the flowfield of the primary. The trim swashplate deflections and linear responses are compared at various positions of the secondary helicopter with respect to the primary. The results show that while the trim swashplate positions vary greatly between the different cases, the linear response remains unchanged. Next, a flapping controller is developed and a time marching simulation of the secondary rotorcraft traversing the wake of the primary shows actuator usage requirements for various air speeds. The faster the secondary helicopter traverses the wake, the larger the swashplate displacement required. The swashplate limits were not reached for either scenario evaluated.