Unveiling its Blue Edge advanced rotor blade at this week's Heli-Expo show in Houston, Eurocopter says flight tests have shown the "double sweep" tip can halve a helicopter's noise profile on the descent.
The design reduces the noise generated by blade-vortex interaction (BVI), the characteristic pulsating sound created when the tip of a rotor blade hits the vortex shed by the tip of the preceding blade. Eurocopter says the Blue Edge tip shape gives more time for the interaction between the blade and vortex, attentuating the noise.
A five-blade Blue Edge rotor has been in flight test since July 2007 on an EC155 testbed, logging 75 flight hours and demonstrating noise reductions of 3-4dB, the European manufacturer says, adding that the design is now ready to move into production. You can get an idea of the noise reduction in this Eurocopter video.