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6 Answers

If a helicopter is hovering and there there is no wind, is the angle of attack the same degree as the pitch angle?

Asked by: 961 views Aerodynamics, Helicopter

Say the only component of the  air velocity acting on a rotor is the tangential velocity to the rotor blade at various points along the radius.  Due to there being no vertical component (climb) would it be safe to say the pitch angle and angle of attack are equal?

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6 Answers

  1. Best Answer

    Russ Roslewski on Dec 09, 2016

    I’m pretty sure the Helicopter Flying Handbook, page 2-10, regarding Induced Flow is the answer you’re looking for. The induced flow, even in a hover with no wind, reduces the AOA somewhat. Therefore, it would be different than the pitch angle.

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  2. Kris Kortokrax on Dec 09, 2016

    Further, it makes a difference if the helicopter is hovering in ground effect versus out of ground effect.

    This is kind of like a dog chasing a car. When it catches the car what will it do with the car?

    Now that you have the answer to your question, what will you do with it? The situation you describe would seldom be encountered. Completely windless days are few and any aircraft that would remain stationary would be of little use.

    We attempt to answer most every question posed, but I wonder what would prompt this question.

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  3. Dallan on Dec 09, 2016

    Thanks Russ, Appreciate it!

    What prompted me to ask such a question is i’m an engineering student carrying out a study on drone rotors and I’m designing and manufacturing some lets say small scale drone props. I’ll test these props physically to gain some static thrust results along side some computational fluid dynamics and theory based calculations then analyse compare and conclude on some theory!

    This should give you an idea of why I’m asking and what I intend to do!

    Thanks for that analogy by the way kris, hopefully I don;t get run over along the way !

    Dallán –

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  4. Kris Kortokrax on Dec 09, 2016

    I figured as much. The question is not one that would come up during normal piloting. I’ve not paid much attention to drone rotors, although I suspect that the blades have the same kind of twist that helicopter rotors have, meaning that there is an attempt during design to equalize lift across the blade.

    The reference to IGE and OGE is probably meaningless for a drone.

    You mention drone props as well. With as much research as has been done on propellers over the years and the NACA and NASA databases of airfoils, is there much room for innovation?

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  5. Dallan on Dec 10, 2016

    Yeah, I believe they do also for drones!

    For more commercial based drones I’ve the notion that the design is more trivial and not really scientific.

    In my opinion designers haven’t really pre-hand predicted their rotors performance and more than likely use a physical test to gain results! I’ve done a good bit of looking there’s not a substantial amount of research on drone rotors specifically and mainly I’d like to be able to develop some data which would allow drone enthusiasts to choose a specific blade for a specific performance or application knowing the results proven!

    There’s alot of useful information from NACA reports that are applicable but are difficult to interpret at times.

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  6. Abner on Mar 19, 2017

    No. The AOA and pitch angle will never be the same as long as there is induced flow.

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