A novel application of harmonic wake methods for propellers at incidence have applications for compound helicopters. Any hingeless rotor subject to non-uniform incident velocity will produce a constant force in inertially-fixed axes (i.e., reacted on the non-rotating support) - though this phenomena is well-documented, engineering-level models for prediction of this force are generally poor, and tend to utilise assumptions that have little physical basis. To avoid utilising these assumptions, a harmonic load/wake model is presented that affords the ability to model blade-level unsteadiness without time-marching, includes three-dimensional blade effects, and allows whole-disc load resolution at the same computational cost as the referenced current 'best practice' models. Furthermore, the fundamental equations that convert harmonic blade loads into steady inertially-fixed forces are reviewed, and shown to be missing a large component of the force resolved into inertially-fixed axes. Finally, detail is provided of a current wind tunnel experiment aiming to provide validation for the harmonic wake model.
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