As an ex-RAF QFI, would someone please tell me how to unstall a wing using rudder ?

Now, I know you're being facetious Dook, but...

If a wing is stalled you need to reduce its angle of attack to unstall it. Put in a boot full of rudder and you lengthen the forward vector and the AoA of that wing reduces: the wing unstalls. Of course the yaw has the opposite effect on the other wing. I think that is a popular way of entering a spin.

But the application of rudder has unstalled a wing!!!

I'll get my coat.

I'll have to tell the Central Flying School that and tell them they have been wrong since 1912 !!!

The physics is correct; I'm not suggesting that this is what you'd want to do to recover from a stall. But you did ask:rolleyes:

Sorry old chap, but the physics is totally incorrect.

I must have taught aerodynamics incorrectly for twenty years and so must a retired test pilot friend.

OK, justify.

The AoA is the resultant of the descending (vertical) line of the stalled wing and the forward motion (horizontal line) compared to the chord. A boot full of rudder increases the length of the horizontal, thus the AoA reduces. On the other side of the aeroplane the opposite happens, hence the likelihood of a spin the opposite way to the original wing drop.

I have no further interest in this.

Goodnight.

Fair enough.

Kemble

Even if one accepted that yawing the stalled wing forward reduces its angle of attack, and I'm not convinced, that is not to say that the angle of attack will be reduced sufficiently to unstall the wing. An upgoing wing does not necessarily = an unstalled wing. A perfect spin scenario: stalled, rolling and yawing.

Incidentally, in a climbing turn with a shallow angle of bank and at the stall, with certain types, a sudden and rapid wing drop of the outer wing can happen. Whenever possible I would always demonstrate this.

I'm with Dook and Frog on this.

The upgoing wing may then unstall as the spin develops - that is believed to be the case quite often, but it doesn't stop the spin self sustaining.

G

One exercise I like, which seems to be seldom taught is to link climbing turn stalls with slipping and skidding. I deliberately set up the slip or skid with too much rudder in the desired direction. If the airplane is slipping then the aircraft rolls toward level as it stalls, but if it is skidding it will tuck under inside the turn.

Just saying "skids are bad" doesn't deliver the message half as well as showing people why getting slow and skidding, especially at low altitude is deadly. The overcooked base to final turn with the lots of inside rudder is also a great exercise, however unfortunately some trainers like the C172 are so docile it is hard to do a convincing demo of the skidding base to turn stall. incipient spin

This is an interesting debate (and if I offended Dook in some way that was certainly not my intention by the way).

Going somewhat back to the area of the original posting about wing drops at the stall.
It used to be taught, and you can easily go and show it in action, that you should pick up a wing drop at ther stall using rudder rather than aileron (for the purposes of this argument please ignore the multiple pros and cons of either action).

Next time you go flying, and at a suitable height, do some stalling and hope to get a wing drop. Try 'picking the wing up' with a boot full of rudder before unloading the stick. The dropped wing will get picked up - also, as their is ought for nowt as our Northern friends say, the other wing will, likely, then drop instead. We recognise this as spin entry but forget that for the moment also.

So, the wing that dropped first was the one that stalled slightly earlier than the other one - I suggest that the only way its going to stop falling and then come back up is if its 'flying' again, and is now unstalled. I also suggest that that is the result of increasing the wing's forward speed (thus reducing the AoA) as a result of yawing which is the result of the boot full of rudder.

But I am intrigued as to why this is contentious.

[For the avoidance of doubt, this is not the best thing to do to recover from a stall - SSR is release the back pressure, apply full power and then (when the wing is flying again) sort out any roll].

Views please.

I imagine the part of this that may be contentious is that by using the rudder to lift the wing, you are not necessarily "unstalling" the wing even if it is having a lower AoA, you are just allowing both wings to stall more evenly.. the lifted wing isn't necessarily "flying" again.

...so ultimately you MAY have made it less dangerous (by some remote margin), but you haven't really fixed the problem

Onionabroad

For clarity, I am not suggesting that this is a good or a bad idea, just postulating that this is what happens if you use the rudder.

oh I know... I'm just speculating on why some may have strong feelings against what you're saying.

For those who know little, and there seem to be quite a few, an inverted spin in a Hunter from 40,000 ft would provide an interesting experience !

I've expressed already that I am not convinced yawing the wing will unstall it. However, if you have some faith in this idea you also have to ask the question: to what point in its travels can it be known the wing has been yawed sufficiently? Surely it is not being suggested that the wing can only be unstalled when it is "level" but with what. So, what could be the reference for "levelling the wing". The horizon should take no part in stall recovery.

Pitching to reduce the A of A below the critical angle requires no reference datum. It is sufficient to know that the reduction is achieved by reducing back pressure. This is easily demonstrated.

Sorry Dook, but it does seem that you can provide a lot of 'there I was with nothing on the clock but the makers name...' it might be helpful to profer some actual theory to further the discussion.

I've spun a Hunter inverted. Enter at 30,000ft, 4 turns, recover, pull out from the dive - bottoms at about 15,000ft. Concentrated the mind on height loss - but as it's a swept wing jet massing around 10 tonnes, not all that representative of light GA typically massing about a tonne, with a propeller and a straight wing.

G