Is the cross section of both a Trailing edge flap and elevator an aerofoil please or, like i've shwon in in image below? I tried to find a side view of an elevator and TE deflected to see this for myself, but couldnt find one

enter image description here

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    $\begingroup$ I can't help but notice that in the past few days you asked several questions about basic aeronautical and aerodynamics concepts. I'd suggest you to read a good book about those concepts instead: getting a lot of answers from random guys on the internet is definitely not the best way to learn this kind of subject. "Aircraft performance and design" by Anderson is a classic. $\endgroup$
    – sophit
    Commented Oct 27, 2023 at 14:20
  • $\begingroup$ Hi Sophit, thanks for the book. I swear I did do research into this question, but just haven’t been able to find anything. $\endgroup$
    – SirTimothy
    Commented Oct 27, 2023 at 14:47
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    $\begingroup$ What do you think this image represents if it is NOT an airfoil with deflected trailing edge? I'm just not understanding your confusion here. If you have done enough research to locate an image like what you posted, it would seem that you would understand what it represents from the context where it first appeared. $\endgroup$ Commented Oct 27, 2023 at 15:30
  • $\begingroup$ I generated that image in cad Michael- I just wanted to know whether the cross section of an elevator and flap is an Aerofoil or like I’ve done $\endgroup$
    – SirTimothy
    Commented Oct 27, 2023 at 16:06
  • $\begingroup$ What you have done is an airfoil, with a hinged trailing edge. (roughly...) Is that what you were trying to create? $\endgroup$ Commented Oct 27, 2023 at 16:33

1 Answer 1


Many elevators have airfoil shapes.

The precise way you've drawn the flap is not physically possible. It is drawn as a shear of the trailing edge. That would involve deforming materials.

Instead, a control surface has a hinge and there is a rigid body rotation about a single axis. This usually means that the front of a control surface is an arc about the rotation axis.

enter image description here

On small general aviation aircraft, it is not uncommon for the elevator to be made out of welded metal tubing and covered with fabric. In this case, the elevator (and its control surface) will be flat plates with circular leading and trailing edges.

Empennage of a Cub

In general, to prevent control surface flutter, control surfaces need to be balanced (mass) around their hinge. In addition, it is often beneficial to add some sort of aerodynamic balance in front of the hinge. This is an extension to the surface that reduces the force required to deflect the surface.

  • $\begingroup$ Hi Rob, can I ask for the book you got those nice pictures from please? $\endgroup$
    – SirTimothy
    Commented Oct 28, 2023 at 11:51
  • $\begingroup$ No book, just a random website. I did a google search for control surface hinge or something like that. $\endgroup$ Commented Oct 28, 2023 at 17:07

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