# Does the size of control surfaces affect maneuverability, and if they are smaller, is it easier to stall?

Does the size of control surfaces effect maneuverability and make it easier to stall?

• As the lift force produced by a control surface is proportional to its surface, the manoeuvrability is affected by their size. – H.C. Lefevre Sep 30 '16 at 8:14

There are at least 3 possible cases and unfortunately your question doesn't tell which one you would consider valid.

The maneuverability (the maximum rate of rotation?) can be measured by the moment of the force exerted by the surface at the CG.

Let's consider the area of the control surface is smaller, and...

1. All other parameters are unchanged, in particular surface airfoil, center of pressure, and angle of attack:
• As the currently selected answer tells, the maximum lift available from the control surface is lower, hence the maximum moment is lower, and the maneuverability is reduced.
• As the airfoil and the angle of attack are unchanged, the stall characteristics are unaffected.

This theoretical case is unlikely to be seen as the designer would certainly compensate the reduction of the area by some other change.

2. The surface is moved to a location further from the CG to maintain the moment with the smaller lift force:

• Neither maneuverability nor stall characteristics are affected.

3. The angle of attack is increased to generate more lift and compensate for the smaller area:

• Maneuverability is decreased as the maximum lift obtained with the maximum angle of attack is decreased.

• Stall is easier to trigger as the angle of attack (for an equal moment) is closer to the stall angle.

• any of the four cases! – anonymous Oct 1 '16 at 13:32
• If by 3 you mean increased deflection, then the airplane stall will be (more or less) unaffected. (I suspect the OP meant airplane stall). It may be easier to stall the control surface itself, but not in all cases (e.g. when pulling up near the airplane stall). And if we don't approach surface stall, then the overall control efficiency (and thus manoeuvrability in this sense) can be pretty much equal. – Zeus Oct 3 '16 at 3:16
• @Zeus: Thanks for the comment (I believe that's correct for elevators, but is less applicable to canards). I agree my answer is not a great one and needs to be refined. – mins Oct 3 '16 at 8:49