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Retreating blade stall in retreat..

Community Veteran
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Registered: 01-08-2007

Retreating blade stall in retreat..

Yup, those clever yanks some 30 years after Airwolf, have finally worked out how to get around retreating blade stall on helicopters which normally limits them to a max speed of 200mph.
They're using contra rotating blades to ensure there is lift (along with loss of it) on both sides of the fuselage. This lets the machine fly faster than the 200mph limit!
Exciting stuff!!! It had to happen eventually.. with the tilt rotors threatening to put the traditional helicopter out of business, somebody had to solve it!
http://www.dailymail.co.uk/sciencetech/article-3101718/Batmobile-skies-takes-flight-Sikorsky-tests-r...
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Community Veteran
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Registered: 23-09-2010

Re: Retreating blade stall in retreat..

Yes it is amazing.
The "warp barrier" of helicopters passed.
Will the new breed of helicopters still look like helicopters as high speed factors come into play?
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Re: Retreating blade stall in retreat..

I've been flying contras for years but they rarely exceed 15mph under my control (RC models).
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ffox
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Re: Retreating blade stall in retreat..

Trust the press to tout something invented in 1754 as new!
http://en.wikipedia.org/wiki/Coaxial_rotors
The retreating blade problem is only part of the story.  The Wikipedia article is quite good but omits to mention the problem with the advancing blade.  If the forward speed is high the tip of the advancing blade can reach the speed of sound which makes it inefficient and noisy.  This is why we do not have supersonic prop-driven planes.
As the article states, a single blade produces torque which attempts to turn the fuselage in the opposite direction.  Contra-rotating blades balance out the torque .
With two rotors the blades can be much shorter than single rotor blades or else turn slower.  In either case the retreating blade stall and advancing blade sonic problem will not occur until greater forward speeds are reached,
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Re: Retreating blade stall in retreat..

Quote from: ffox
Trust the press to tout something invented in 1754 as new!

Well it is new when it comes to breaking the speed limit for a normal helicopter  Tongue Wink
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Re: Retreating blade stall in retreat..

Just as interesting on the same page was mention of a skytrike, early days but imagine if they got that to work we would all be on our bikes then.
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ffox
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Re: Retreating blade stall in retreat..

Quote from: 7up
Well it is new when it comes to breaking the speed limit for a normal helicopter  Tongue Wink

Normal?  As the press article says it features 2 rotors that turn in opposite directions (quite common) and a pusher propeller (very unusual).
Being old and cynical I view popular press stories with suspicion.  A quick google turned up the Eurocopter X3 which has similar features and went 17 mph faster 2 years ago:
en.wikipedia.org/wiki/Eurocopter_X3