Wing drop at stall
 

The thread linked below is from many years ago, but you might find it interesting:-

http://www.pprune.org/flying-instruc...op-stalls.html

Current instructor training is to teach students to unstall the wing (stick forward, enough) whilst adding full power. Once the aeroplane is flying again, only then sort out the roll.

I'm with you on the spin risk, although it is often over-stated, but even so.

Out of interest, current aircraft certification requirements actually demand that the ailerons are fully effective all the way into the stall. However, older aircraft (pre-1960s) might not be so amenable so I think its best to teach students to stay off the rudder and ailerons altogether until the aeroplane is flying again.

All ab initio stall training should start with the understanding that the point of the exercise is not to teach you how to stall the airplane, it is to teach you how to recognize the aircraft is about to stall and fix the situation before it does stall. However if you are asleep at the switch then it is important that you learn how to quickly regain control. This should always start with reducing angle of attack by smoothly but firmly lowering the nose and then applying full power. Control of yaw at this point now becomes important as if the aircraft is allowed to yaw then it can spin. Effective use of the rudder is the way to control yaw and thus eliminate the possibility of the aircraft departing in a stall.

Even though modern aircraft certification standards require that the ailerons be effective even after the wing has started to stall, ailerons should still not be used to level the wings until the aircraft is definitely un-stalled

The biggest problem I see with ab initio instruction is the exercise is taught with the aim of generating a good mark on the flight test, instead of showing students the real world scenarios that pilots get into trouble on.

That may be the consequence of what you do, but the correct teaching is to move the control column centrally forward. That may or may not lower the nose.
The rudder is used to prevent further yaw

Hopefully you can open this, which was a fairly extensive research into optimal recovery actions.

https://www.aerosociety.com/Assets/D...urnal/3965.pdf


If that didn't work, try this link:

https://bura.brunel.ac.uk/bitstream/.../Fulltext.docx

It didn't actually look into the absurdity of picking up a dropped wing with rudder, which I think most of us know more correctly by the name "spin entry". It concluded that optimal recovery is simultaneous pitch and power in all singles tested.

G

It was suggested at a FIE standardisation meeting some years ago, by a fairly senior former RAF QFI that the practice of using rudder at the point of stall came from training on the Harvard. When the aircraft dropped a wing, the weight of the engine lead to increased yaw and the use of top rudder in the recovery would minimise the height loss. Unfortunately, this technique was passed on to many new instructors, who were trained in the 60s by FIC instructors who might have been trained on the Harvard.
Following a rather nasty accident in a Slingsby involving "oscillatory stalling" the practice of trying to pick up a wing with rudder was discouraged by the CAA.

Given the Harvard's well known reputation for spinning off a stall, particularly if inadvertently stalled in the final approach configuration - that is "interesting".

I just took a look on the national archives website, but unfortunately can't seem to see any A&AEE flight test reports on the Harvard - it would be really interesting to compare that supposition to the published characteristics of the aeroplane.

I did find this webpage with a set of what appear to be wartime USAF training notes for the Harvard....

https://www.t6harvard.com/pilot-stor...nd-manual-pdf/

If you download chapter 5, and go to page 62 you find...

It goes on for several pages after that, but so far as I can see, every mention of the rudder is about either preventing further yaw, or keeping the ball in the middle. It repeats several times what we'd still say now - unstall the aeroplane with elevator, then use the ailerons to roll wings level.

G

Which could have been misinterpreted to mean pick up the wing with opposite rudder. So many old school instructors taught this that it had to have originated somewhere, with a little bit of "Send three and fourpence, we're going to a dance"

Might have been on some other type? I certainly agree that it's a bad practice anyhow.

What works on a Tiger Moth?

G

We, all too often and unwittingly confuse the central aim of recovery from the stall, with the process. The first aim must be to unstall the wing(s), nothing else.

Applying power will not unstall the wing(s). The rudder will not unstall the wings. In my view it doesn’t matter whether you move the hand control forward centrally or not, what really matters is that you stop holding back.

The aircraft cannot stall on its own; it takes the pilot to do it. So if stalled the pilot must be pulling the control aft. The inherent pitch down moment will be so strong the pilot needs only to relax the back pressure; the aircraft will do the rest. The angle of bank, if any, is irrelevant and should the aircraft be turning, so what.

After unstalling the aircraft and regaining control, then and only then does achieving the minimum height loss becomes paramount. Applying power and levelling the wings is a major part of this of course. Incidentally, with regard to the Harvard an old mentor would regularly refer to how quickly, during stall recovery, you could put a Harvard on its back with too much power if also applied too early.

However, having applied power then control of pitch, roll and yaw will be required with the simultaneous use of all three controls. During the olden days when the CAA had a flight examiner wing an internal argument raged; some saying “the simultaneous use of power and pitch ...” for recovery but this would send others into a state of apoplexy whilst banging the table and demanding hysterically that you must say “pitch and then power...”. The late great Hector Taylor when asked for his view replied: “the simultaneous use of pipowtcher...” was how he said it. He explained that it was the only way he had found to say pitch and power at the same time.

Absolutely! It was taught to me purely as a 'task' to be competed without changing altitude or direction. I would like a more real world scenario, eg simulating a slow turn to final in which I am daydreaming, let airspeed fall during the turn and suddenly find myself in a stall with one wing low. I understand that is a common way to die, so it would seem to be worth to build-in the correct instincts for such circumstances.

Do you mean to say that you were never taught nor examined whilst stalling in the base turn?

Yes. Only from straight and level with varying amounts of flap.

GtE

A (properly rigged) Tiger Moth will usually just stalls wings-level withou a wing drop and with a high rate of descent, so unstall the wing and add power and away you go. To be honest, with such a deficiency of aileron its pretty hard to make a Tiger go around a corner anyhow...

On the Harvard you simply unstall the wing, add power and then deal with the (rather large) wing drop. Did that a couple of weeks ago on a re-check ride and it seemd to work just fine.

db
May I ask which country you trained in?

A few years ago there was an incident in the UK where a Microlight pilot was killed in an accident following a stall. On investigation, it was found that his Training Records had been falsified and that he had not completed the required stall training. The Instructor received a 6 month sentence.
Every test, club check etc that I have ever conducted has involved stalling in the turn, and you have never done this, it is also one of the major reasons for failure.

Not the UK!

I have sometimes been with pilots in their LAA aircraft for the one hour with instructor and say to them lets do some stalls.
Usual reply is, they have never stalled the aircraft.
So i ask them, well how do you know what a safe airspeed is on the approach and landing.
Often they say the previous owner said fly it at a certain (too fast) speed.

Lets face it, if a stall and wing drop occurs, the first thing a pilot will do is probably full opposite aileron.
It will never happen in a clinical practise way.

Exacerbated by the LAA not historically ensuring a properly populated and checked POH! (Although that does seem to be changing with the latest types.)

G

Let's be fair to LAA here, you don't need a POH to take your aeroplane up to 5000 ft and see how it stalls clean. dirty, dirty/turning. You need to be taught to fly properly and you'll then understand that stalling is not scary and its a good idea to know how your aeroplane behaves.

When giving people 'biennials' I always get them to stall straight and turning. Most of them gibber when I show them turning stalls (some for stalls of any sort), some actually sweat, and they are often too nervous to really do it themselves with me next to them. I've often had to complete the 'back stick' pull to get the thing to stall as they just can't bring themselves to do it. Maybe that shows a good degree of self preservation but I'd rather they experienced the full stall and practised the correct recovery and made it automatic.

Bottom line is most (GA) pilots are scared of stalling, possibly because most instructors are too. I do my best to overcome this during the biennial '1 hour'.

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