Eurocopter Blue Edge rotor blade noise reduction

[Richard Lightstone, CAS]

From Gizmodo: Helicopters make a lot of noise because of a physical phenomenon called blade-vortex interaction. Eurocopter engineers have developed a new kind of rotor blade that attenuates this problem. It's called Blue Edge, and—as you can hear—it works beautifully:

The new blade shape is combined with another technology called Blue Pulse, which adds three flaps to the edge of the rotor blades. These flaps move up and down at 15 to 40 times per second, using piezoelectric motors that also help to reduce the blade-vortex interaction.

[Tom Visser]

Didn't Blue Thunder already have this with its silent mode?

[Marc Wielage]

Didn't Blue Thunder already have this with its silent mode?

You know, screenwriter Dan O'Bannon used to live within six blocks of me in West Hollywood. We used to get buzzed all the time from crazed LAPD helicopters during the 1980s, and according to legend, he wrote his script after one of the copters drove him crazy in his apartment building for an hour or two.

Trust me, they don't got no silent mode. Just loud and louder.

--Marc W.

[curleysound]

Most of the time cops want you to know they're there...

[RPSharman]

Cool.

[jonathan chiles]

I hope that soon all choppers have to use these! Might make shooting in areas with crazy heli traffic a little easier for us:) as well as keeping us urbanites brainwaves a little calmer?

[DBurnette]

That's neat.

The other noise factor with the Eurocopter (as explained to me second-hand) is the difference between civilian and military versions and options.

Apparently, there is a 'gear quieting' option that makes extensive use of helical involute teeth, instead of involute spurs throughout the main and tail drive shafts. More expensive, much less noise in the 2K-6K range.