6
$\begingroup$

I have this study question on the FIA written:

Which statement is true concerning the aerodynamic conditions which occur during a spin entry?

Correct Answer: After a full stall, the wing that drops continues in a stalled condition while the rising wing regains and continues to produce some lift, causing the rotation.

Incorrect Option: After a partial stall, the wing that drops remains in a stalled condition while the rising wing regains and continues to produce lift, causing the rotation.

Because the only difference between the two answer options is 'full' and 'partial' I was wondering what are the differences between a full stall and a partial stall?

$\endgroup$
5
$\begingroup$

For GA aircraft with straight, rectangular wings, the stall usually starts at the root and progresses towards the tip. So, at some point, only a portion of the wing will be stalled. This is sometimes referred to as partial stall, though it is not a common term.

Partial stall

Image from boldmethod.com

This is usually achieved by having a washout or a wing cuff. In case of root-first stall, the wing tips are still producing lift, helping to prevent rolling motion (which may occur if the whole wings stalls at once), which in turn prevents the aircraft from entering a spin.

$\endgroup$
  • 1
    $\begingroup$ My lecturer told us that it's purposely designed so the stall starts at the root (so the ailerons don't stall first and the pilot still has some control). $\endgroup$ – Taher Elhouderi Dec 12 '15 at 5:37
  • 1
    $\begingroup$ @TaherElhouderi In a manner, yes. This is one of the advantages of unswept wing. Note that some wings have devices to prevent the spreading of stall (like wing cuff etc) once it has started in the root. $\endgroup$ – aeroalias Dec 12 '15 at 13:50
3
$\begingroup$

Sounds like a poorly worded question on the FAA's part. I don't think there is a useful definition of "partial" stall. Most FAA questions come from FAA references like the Pilot's Handbook of Aeronautical Knowledge, so you could check there. Beware that that book and other FAA publications are full of errors.

Vaguely related: If the airplane is rotating (rolling and yawing) but the airspeed is increasing rapidly, then that is a spiral dive, not a spin.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.