The Effect of Blade Tip Sweep Angle on Forward Flight Performance of a High-speed Helicopter

Abstract

This paper discusses the change in forward flight performance and its mechanism when a sweep angle is added to the rotor blades of a high-speed helicopter, based on the results of CFD (computational fluid dynamics) analysis. The results of the study of the concept of maintaining the rotor disk horizontal in flight confirmed that a blade with a forward sweep angle can be expected to provide several percent additional performance improvement. This is due to the fact that the dynamic pressure changes with azimuth angle at the point where the sweep angle is added to compensate for the effect of rotor wake, which reduces the thrust at the aft half of the rotor, making it easier to balance the rotor moment. A detailed discussion of this mechanism is included based on the wake speed distribution and the blade pressure distribution at the relevant azimuth angles.