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10 Answers

Rotor Blade

Asked by: 2780 views Aerodynamics, Helicopter


what is the effect of 2 rotor blade and 4 rotor blade with same engine config.?

Your Wise & precious Advise needed.

Thanks & regard

Arif Marri

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10 Answers

  1. Kris Kortokrax on Oct 18, 2013

    How in the world did you get to be the pilot of a Bell 412 without knowing the obvious answer to this question? Rotor systems are balanced by adding or subtracting washers from locations very close to the mast.

    This would be akin to the pilot of a 747 asking if half a wing broke off would his airplane be controllable.

    The advice I would give is stop flying until you understand basic aerodynamics.

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  2. Lion on Oct 19, 2013

    The best way to tell is to buy a four blades helicopter toy and break one blades in half and see yourself.

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  3. Muhammad Arif on Oct 19, 2013

    Sorry Kris Kortokrax, i ask your advice, you are no one to say i stop flying. keep this suggestion with you, i know what to do. and stop criticizing other.s thanks

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  4. Muhammad Arif on Oct 19, 2013

    Thanks Lion, i thing your suggestion will help.

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  5. Brian on Oct 20, 2013

    I’ve to back Kris here. That is a scary question to hear a twin turbine heli pilot ask. I don’t fly helicopters and the answer appears a pretty obvious one. Of course I own a desk fan from Walmart that had a blade break….

    Kris, it’s mechanics not aerodynamics. 😉

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  6. Kris Kortokrax on Oct 20, 2013

    The resulting dissymmetry of lift would be too much to be compensated for by flapping and feathering. It is aerodynamic and would render the helicopter uncontrollable.

    The other, more important consideration would be the resulting imbalance of the rotor system. It would in all probability tear the mast and transmission from the helicopter, destroying it. Force = mass times acceleration. Call that mechanical if you wish.

    Due to the mass difference, there is no correlation between the toy and a real helicopter.

    Google “ground resonance” and see the result of an imbalance due merely to the rotor blades being out of phase. Some years ago, I saw a Cessna 150 which had landed after losing a propeller tip. The imbalance nearly tore the engine off the mount. The pilot was fortunate to get the airplane on the ground in one piece.

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  7. Kris Kortokrax on Oct 20, 2013

    Should have said look on YouTube for “ground resonance”.

    Also, model helicopters are able to hover upside down. That in no way means that a real helicopter could do so.

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  8. Brian on Oct 20, 2013

    “Call that mechanical if you wish.”

    Exactly. The structural integrity seemed more predominant to me. That’s mechanical.

    I read something similar in one of my books, can’t recall the aircraft, but the author lost a large section of a two bladed wood prop. Immediately he shut down the engine and made a forced landing. The stress from the few seconds the engine ran sheared 3 of the 4 mount bolts.

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  9. Muhammad Arif on Oct 21, 2013

    thanks dear.. Got the point..

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  10. Ron on Oct 22, 2013


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