In recent years, various strategies for the concurrent operation of fixed- and rotary-wing aircraft have been proposed as a means of increasing airport capacity. Some of these strategies, however, may increase the likelihood of encounters with the wakes of nearby aircraft. This thesis analyses a helicopter rotor’s response to an interaction with an idealised aircraft wake by performing a systematic investigation of some of the properties of several frequently used computational techniques when each is used to model the aeromechanics of a helicopter rotor during an interaction with an aircraft wake in and out of ground effect. In previous studies the mutually induced distortion of the wakes of the rotor and the interacting aircraft has been neglected, as has presence of the ground, yielding the so-called ‘frozen vortex’ assumption. This assumption is shown here to be valid only when the helicopter encounters the aircraft’s wake at high forward speed out of ground effect. At the low forward speeds most relevant to near-airfield operations, however, injudicious use of the frozen vortex assumption may lead to significant over predictions of the helicopter’s thrust and flapping. The mutual deformation of the rotor-wake and interacting vortex, in and out of ground effect, is a significant contributor to an observed reduction in the interaction-induced rotor response as the forward speed of the helicopter decreases. Results presented here suggest that vortex encounters under terminal flight conditions in the near-airfield environment may not pose as significant a hazard to operations as has been previously thought.