THE FLIP-TIP ROTOR: A CONCEPT FOR REDUCING HELICOPTER ROTOR NOISE

摘要

One of the major hindrances to expansion of the rotorcraft market is the high-amplitude noisernthey produce, especially during low-speed descent, where blade-vortex interactions (BVI) frequentlyrnoccur. In an attempt to reduce the noise levels caused by blade-vortex interactions, the flip-tip rotorrnblade concept was devised. Increasing the distance between the rotor blade and its trailing tip vortexrnleads to a substantial reduction in BVI noise. The flip tip increases the distance by rotating an outboardrnportion of the rotor tip either up or down depending on the flight condition. Initial results indicate that arn5% radius flip tip can ideally reduce BVI noise in a standard descent condition by up to 12 dB.