Physics of the Proprotor–Wing Interactional Aerodynamics Across the Tiltrotor Conversion Maneuver

Source abstract

The conversion maneuver is one of the most complex and hazardous aspects of tiltrotor operations. The complex interactions increase pilot workload and vibratory wing loads, making it imperative to further understand and accurately predict this dynamic operation. An extensively correlated high-fidelity computational fluid dynamics (CFD) model elucidates the physics within these two-way coupled aerodynamic interactions for a generic model-scale tractor proprotor–wing configuration. Quasi-static evaluations are conducted for proprotor tilt angles in fifteen degree increments to capture the conversion from low-speed edgewise flight to cruise. To assess and quantify the coupled proprotor–wing interactions, additional assessments of an isolated wing at two relevant wing angles of attack and an isolated proprotor operating at all tilt angles were conducted. Wing thickness and loading were mildly correlated with the proprotor loads due to the large proprotor–wing separation relative to the proprotor radius. The proprotor-to-wing effects were assessed using a power spectral density of the wing surface pressure within the proprotor wake. This novel approach elucidates the dominant frequency responses on the wing surface due to interactions with the proprotor wake and directly relates these responses to observable flow features across the conversion maneuver. Overall, this work furthers the current understanding of the proprotor–wing interactions across the conversion maneuver to inform the design and operation of tiltrotor aircraft.