Saturday, May 10, 2014

Learning about stalls and ailerons

Here's the link to an interesting article explaining why not to use the ailerons in a stall and to use the rudders to stabilise the plane. Click on this link.

However there is no uniform agreement on this and if you read below the grahic, South Africa's own Jim Davis on Avcom, has the following to say with his recommendation:

Actually there is no straight answer to this question because it is an type specific thing.

What I can tell you is that with many "modern" aircraft - including the entire Cherokee range - which is 50 years old - the handbook tells you that the ailerons are effective throughout the stall. This is absolutely correct. If you stall a Cherokee by holding the nose in the level attitude until she is fully stalled, you can use the ailerons just fine while she is shuddering and dropping the nose. 

I can not speak for the Cessna 100 and 200 series, or the Beechcraft Bonanza, and Musketeer ranges, but I suspect they are the same.

The theory about the down-going aileron causing a larger angle of attack, and therefore stalling, is simply not correct. What happens is that the down-going aileron changes the aerofoil profile. It makes that part of the wing have a much larger camber, or curve. In fact it turns it into a wing that resists stalling at that angle. Don't believe me? Try this:

Fly your Cherokee, falpless, until it is just starting to shudder on the ragged edge of a stall. Now, without allowing the nose to move, suddenly apply full flap. According to conventional wisdom this should cause the wing to stall - because you have increased the angle of attack on that section. Actually the reverse happens - the flaps put you almost 10 kts above the stall.

HOWEVER don't expect ailerons to puck up a dropped wing in another types of aircraft - particularly the older ones - because many designers, at that stage, hadn't got round to protecting the pilots from their hammy flying!

I should also point out that when training new pilots, it is safer to teach them not to use aileron alone to pick up a dropped wing on the stall. Because that rule covers ALL bases.

In fact, you will get the most positive response by using coordinated aileron and rudder together, on all aircraft. I don't know of any exceptions.

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