Stall recovery techniques

[StatorVane]

Call me a bit pompous but I never thought I'd need to ask this question -especially since I started flying back in 1992!

The problem is this, although I obtained an FAA commercial license (I never used it for commercial privileges mind) there has been a large hiatus where I have not flown. I am back in the air now under the auspices of an excellent instructor but I am struggling to demonstrate good stall recoveries. I cannot ever recall finding this especially difficult in the past and, if I may say, have often been commended as having a good standard of flying. I understand the science of the stall perfectly well so that is not the issue. I wonder if I am hodgepodge of different instructors styles and technique? Or is there a benchmark standard tecnique (assume standard PA28 types)?

In the stall, which I can recognise ok, I have an ingrained tendency to want to push the nose below the horizon but not dive of death style just enough to put gravity in our favour as opposedto against. I also simultaneously give a smooth application of full power (if not already at full power). I think this must be how I was taught since in all the flight tests I have ever done (8 I think in total for various national licenses and conversions etc) I have never once been picked up on stall recover technique! I DO want to be pulled up if I am doing something wrong but would also like to know if there a number of "accepted practices" when it comes to this especially under examination.

I do remember a long while ago a debate about different techniques and maybe things have evolved since then. For the sake of clarity and for the record I would like to hear what you guys think about stall recovery techniques in different configs and compare this with what my instructor is saying.

Thanks and much appreciated....

[Radix]

.............

[RTN11]

The only objective is to recover safely from the stall with minimum height loss.

If you are losing a load of height then your instructor may well have a point. If not, then get him to demo one and then point out that he is losing just as much height as you.

In a PA28 fully developed clean stall I would expect a minimum of 70' height loss, from a typical PPL I would accept around 100-150', and 200' would really be pushing it. This obviously increases with flap setting.

The standard technique for any aircraft is exactly what you describe. If you are not pitching down to the "dive of death" then perhaps you are lingering with the nose down just a bit too long for this particular instructor's taste. Ultimately as long as you are leading with the pitch down, following with power, trying to stay in balance and recover to a climb then that is all I would want to see.

[Genghis the Engineer]

I've been (professionally) working on this for several years and hope to submit a rather lengthy paper for peer review shortly.


In a nutshell however, we found:-

(1) Stick forward to unstall the wing.

(2) Increase power to reduce height loss

(3) The bigger a gap between unloading the wing and increasing the power, the more height loss.

(4) No gap between stick and power is fine, but in some types applying power first will cause it to do nasty things, so don't. (One or two types you can power out of the stall, but this is unpredictable and generally speaking, not a good idea.)


Strangely enough, this almost exactly matches the official CAA publications.

It does not match the FAA publications which will unstall the wing, THEN apply power - a non-zero-gap in other words. This adds around 50% to the height loss.

We never found any aeroplane type, in any configuration, that would do anything more than mildly uncomfortable if power and pitch were done together.

All experience, mine and many others, is that more stick movement than was needed to unstall the wing will simply increase height loss. It gains nothing useful. So, slightly more nose-down than the level flight attitude is perfect.

G

[hugh flung_dung]

Stick sufficiently far forward to un-stall the wing - this means remove the symptoms of the stall
Full power (all relevant levers), while preventing further yaw with rudder
Level wings with aileron
Smoothly pitch to safe attitude (usually cowl on horizon)
Set configuration (gear & flap)
Adjust power and attitude

Some people feel uncomfortable using full power in a training situation but this can be trained in/out of them. Many studes do not know or recognise the primary symptoms of the stall (buffet, un-commanded roll) and therefore leave the nose down far longer than is necessary ... that's where the training is often needed.

HFD

[Big Pistons Forever]

So, slightly more nose-down than the level flight attitude is perfect.

G



Genghis

I very much respect your professional knowledge, however I must disagree with the above statement. Cessna 150's and C 172's with the 40 degree flap setting, which represents a substantial part of the training and rental fleet, will stall at an almost level flight attitude. They will also when close to the stalling speed ( ie backside of the power curve) not accelerate in the level flight attitude. It is very important if these airplane stall with full flap to hold the nose well below the level flight attitude while full power is applied and the flap is raised to 20 degrees.

Personally I think too much emphasis is placed on the "right way" to recover from the stall and not enough on recognizing an incipient stall and recovering before the stall happens. The accident record shows that base to final turning stall/spin, the low and slow final approach (usually full flap and low power) and the after takeoff departure stall (no or takeoff flap and full power) are the ones where the outcome is usually a smoking hole with dead bodies. Surviving these situations is not performing a good stall recovery, it is avoiding stalling in the first place.

The "pass the PPL flight test" stall performed at altitude in the practice area is not IMO a very useful manoever in preparing students for the real world danger zones they will encounter.....

[Willie Everlearn]

Ghengis,
I'd teach you this way.
(the type of aircraft and engine is relevant. The OEM stall recovery technique should take precedence over the PTS and you can look for the FAAs amendment)

Lower the nose to reduce the angle of attack.
2 or 3 degrees should suffice but more may be required. How much nose up prior to entering a pre-stall might give give you a clearer indication of how much nose down is needed in recovery.

apply the necessary power (not always Maximum), overboosting could cost you.

ensure wings level

Maintain level flight

Determine flight state based on stability, controlability, and airspeed.

Return to your assigned or previous FL or altitude.

Finally, a minimum loss of altitude has NO numeric value. It is realistically any altitude that does NOT result in ground contact. Practically however, it should be a reasonable loss based on manufacturers recommended recovery technique.

Have fun out there.

Willie :ok:

[Dan Winterland]

For the first action:

How about "Control column centrally forward until the buffet disappears". It's simple, direct and unambiguous.

It's what I learned at CFS and emphasises the point that while you have buffet, the aircraft is still stalled. Attitude should not be relied on as stalling is not attitude dependant.



Genghis - would love to volunteer to be one of your 'peers' as I had a hand in your study!

[Genghis the Engineer]

BPA - as we know, an aeroplane can stall at any attitude, so there's an element of judgment here, and as Willie rightly says, if there's a POH recovery, that takes precedent over all else.

But aeroplanes where you wouldn't use full power are a rare and special case, and certainly for the standard warrior/archer/cherokee/arrow family that I assume the OP was talking about full throttle would certainly be the norm. (For that matter, whilst I don't have a POH to hand, I'm reasonably certain that's the norm for the few times I've flown a turbo-arrow as well).


Dan - I'm putting it into Aeronautical Journal, so the reviewers will be whoever the Royal Aeronautical Society decides to appoint. But thanks for the offer, and you're very welcome to see a draft and give me opinions (not the journal's formal peer review, but no less appreciated) when nearly there which would be great to have.

G

[fwjc]

How about "Control column centrally forward until the buffet disappears." This assumes buffet. That doesn't always happen.

[Pilot DAR]

The responses mostly say to lower the nose/reduce the angle of attack/unload the wing, which I certainly agree with. It seems "how much?" is the question. I think that simply stopping the buffet may not be enough.

The wing stalled because the load on the wing exceeded its ability to lift. The load will always be present because of a trimmed or untrimmed elevator input to maintain or increase the G loading on the aircraft (yes, usually we're just trying to maintain around one G). If for any number of reasons, the wing cannot provide the required lift, it will stall. To recover that, remove the demand for the wing to carry the load = stick forward.

The instant the stick moves forward, the recovery has begun, now its a matter of how much more to move the stick forward, and how much space below you the is for the plane to move into while you do it. Letting alone the issue of how much space is below you for now, its all about angle of attack. This might have some relation to the horizon, but maybe not so much as you think.

As Big Pistons points out, Cessnas with 40 flap out can be stalled in near level flight, a Twin Otter with full flaps can be stalled with the nose quite down. (its alarming to do a full stall landing, and still three point a tricycle!) On the other hand, one can briefly fly most any plane at speeds less that "stall" speed, by doing so at less than one G.

I am not an instructor, so it would not be right for me to pronounce teaching and qualifying techniques. It is, however necessary to recognize the need to rapidly change the attitude of the aircraft to prevent/recover a stall. If it is an unintended stall, you should not be goofing around with half hearted measures. Get the pitch attitude to be much less - quickly. In this case, too much nose down is better than too little, and having to recover the stall again seconds later. The lower the nose below the horizon, the more quickly the aircraft will accelerate to flying speed.

Power (while maintaining yaw and roll control) is your friend, but if you're flying an aircraft without power, you'd better not be relying upon it to assist in your stall recovery. The reaction to recover the stall, and control and fly the plane, should be first - power just reduces altitude loss during recovery.

I do hundreds of test stalls a year in all kinds of aircraft. Aside from those where power is applied to assess handling with the effects of power during stall/recovery, or record minimum altitude loss, all recoveries are power off to the point of a gentle dive. Demonstrating minimum altitude loss is usually not my intention.In certain configurations, I have had the nose lower than 45 degrees below the horizon during recovery, and never had a concern. Its the intentional stalls in multi engine aircraft, with very asymmetric power, which keep the adrenaline flowing!

[Ex FSO GRIFFO]

'SV',
You didn't mention just 'how' you levelled the wings...

Perhaps you had a tendency to use the ailerons in your raising of the dropped wing? You should ensure that the ailerons are kept 'neutral' throughout the exercise, and pick up the dropped wing with opposite rudder application...
LOTS of opposite rudder - if that's what it takes.

One way to ensure that you do not inadvertently use the ailerons, is to 'lock' your elbow slightly, so that you will keep it level, and therefore, hold the ailerons level.
The rest of your recovery sounds reasonable....
Rudder to hold those wings level,
Throttle full
Nose attitude just below the horizon or as required in your circumstance
Pull out of the ensuing dive to regain lost alt.

Discuss with your instructor, and happy landings....:ok:

[mad_jock]

There is still a bunch out there that really really want an almost power out.

And FAA and various other people producing documentaion that its not the way it should be done has just annoyed them.

They want a ball hair of a nose drop and max power and hang in there using boots full of rudder until it eventually comes out of it with 50ft or less of height gone.

Get another instructor.

[Genghis the Engineer]

Perhaps you had a tendency to use the ailerons in your raising of the dropped wing? You should ensure that the ailerons are kept 'neutral' throughout the exercise, and pick up the dropped wing with opposite rudder application...
LOTS of opposite rudder - if that's what it takes.

Hmm lots of rudder close to the stall. Like spinning do you?

One way to ensure that you do not inadvertently use the ailerons, is to 'lock' your elbow slightly, so that you will keep it level, and therefore, hold the ailerons level.

Oh gosh, I've just inadvertently stalled on finals. Hang on whilst I think about locking my elbows, then I'll do the rest of it....


The rest of your recovery sounds reasonable....
Rudder to hold those wings level,

Most times, places and heights, who gives a stuff if the wings are level, UNTIL the aeroplane is recovered from the stall. Then ailerons are available again anyhow. I'd rather, especially at low speeds, be banked but in balance, than wings level and out of balance.

Rudder to keep the aeroplane balanced. That's what it's for.

Throttle full
Unless, as Willie pointed out, there are good type-specific reasons not to.


Nose attitude just below the horizon or as required in your circumstance
Pull out of the ensuing dive to regain lost alt.

Bear in mind I may have just been recovering from stall on approach, and there may be stuff I don't want to hit in front of me. So surely, achieving a climb is the best response, this can then be fine-adjusted afterwards, but I can think of very few occasions where a controlled climb at or above 1.3Vs isn't a good end point from a stall.

The stall recovery should not be an academic manoeuvre, it should be a lifesaving response to a dangerous condition.

And a dive? Very few stalls should end up with anything as grand as a dive. A shallow descent maybe, but not a dive.

G

[Pilot DAR]

Perhaps you had a tendency to use the ailerons in your raising of the dropped wing? You should ensure that the ailerons are kept 'neutral' throughout the exercise, and pick up the dropped wing with opposite rudder application...
LOTS of opposite rudder - if that's what it takes.

Why?

Isn't "lots" of rudder, with no coordinating aileron, at the point of the stall pretty well a spin entry?

For a certified aircraft, "lots" of any control should not be needed or used during an intentional stall entry or recovery. I once did an intentional (and briefed) stall entry in a DC-3 during a flight test. When I used coordinated rudder and aileron to assure that the ball was in the middle, and the wings were level, at the point of the stall break, the other pilot shouted "don't use aileron!" grabbed the controls, and applied full rudder away from the now dropping wing. I remember feeling the huge yaw, and seeing the ball hard to the side of the slip indicator, as the DC-3 entered a one turn spin to the left. He flew after that - my testing was not continued.

I have never seen a flight manual for a GA aircraft which prohibited the normal use of ailerons during stalls. The closest I have seen is the Caravan, which states that use of ailerons may delay a stall recovery, because of the added drag of an extended spoiler on that side.

Should there be any doubt that "normal" use of the controls is intended for certified aircraft at the approach to the stall, I can offer the wording of FAR 23.201 in part:

Sec. 23.201

Wings level stall.

(a) It must be possible to produce and to correct roll by unreversed use of the rolling control and to produce and to correct yaw by unreversed use of the directional control, up to the time the airplane stalls.

[A37575]

Perhaps you had a tendency to use the ailerons in your raising of the dropped wing? You should ensure that the ailerons are kept 'neutral' throughout the exercise, and pick up the dropped wing with opposite rudder application...
LOTS of opposite rudder - if that's what it takes.


Absolutely fascinating. That hoary old myth has been perpetuated by instructors for decades and here is the proof that it is again passed down the line as fact when it is bull-s...t. Sorry - didn't mean to offend you:ok:

"picking up the wing with rudder" is a term which is grossly misunderstood. The correct message to the student when discussing wing drop during a stall is "use sufficient rudder application to prevent further yaw while simultaneously reducing the angle of attack with forward stick (the amount depends on aircraft type) and use ailerons to level the wings" It is quite wrong to teach the student to use only rudder to literally skid the dropped wing level and is a recipe for a spin in the other direction if insufficient forward stick fails to break the stall.

In many aircraft the design certification ensures the ailerons are effective below the stall. Some wartime aircraft can exhibit sharp wing drops at the stall but the recovery technique has always been as I have described. But never ever deliberately attempt to skid by using rudder to level the wings. It is not only incorrect technique but potentially dangerous as well as being bloody uncomfortable with significant side-loads guaranteed on the fin.

As I commented earlier, it really surprises me that some instructors continue to teach the "pick up the wing with rudder but don't dare touch the ailerons until you have skidded the aircraft level with as much as full rudder... :=

[Ex FSO GRIFFO]

I'll try an say one more time, then I'm out....

At the point of stall, what is the point of trying to use aileron to pick up a dropped wing?
It's probably dropped because it has reached the stall...
So,the last thing you would want to do, is to increase that wing's A of A by putting down its aileron....
The safe alternative is to use the rudder to yaw the wing, thereby increase its speed by that much, and level the wing...as much as it is going to....
If you have gone beyond this, then you are in trouble and aileron ain't gonna help.
So, a combination of ailerons still...neutral.., full power, and rudder as required will let you live another day...
go and try it at a safe alt of course...
Works for me in my Chippy, Tiger Moth, and when I was teaching in Cessnas and Pipers.
The idea of keeping the elbow still is to resist the urge, in some of you apparently, of moving the ailerons to pick up that dropped wing, which is the natural reaction, but IF you do.....bad things will happen.
Go speak to your instructor and heed the advice...:ugh:

[Genghis the Engineer]

Go speak to your instructor and heed the advice.

I count a collection of instructors and test pilots telling you you're wrong.

What instructor should they be going to? One who will tell them to deliberately induce sideslip at the point of stall to pick up a wing that was happy where it was for the moment?

G

[Whopity]

The mind boggles! No wonder students have problems.

[AdamFrisch]

I think the tendency to over correct to get out of a stall, by pitching down quite acrobatically, is a combination of instructor boredom and fear of inducing a spin. That was the way I was taught as well back in the days. Now I just unstall it and not make such a song and dance about it.

[Heston]

The wing is stalled because it exceeds the critical AoA. The elevator controls the AoA. So pitch the nose down. Works without power and I don't want my student stalling and spinning on final turn into the field after an engine failure.

Power should be simply to minimise the height loss.

Dont use roll or yaw until the wing is unstallled - either will make at least part of the wing harder to unstall.

AIUI the "pick the wing up with rudder" thing came about eons ago when aircraft designs allowed a wing tip to stall first - modern designs stall near the wing root first so it isn't appropriate.

H

[Dan the weegie]

I honestly didn't think anyone would ever advocate the use of full rudder to maintain wings level close to or at the stall, or even bring a wing that has dropped, up. I'm quite stunned that there's genuinely someone out there saying it :). I thought it was an urban myth to be honest.

I have nothing to add really, Pilot DAR said it best as is normal.

[Pilot DAR]

The elevator controls the AoA. So pitch the nose down.

Yes. And even better, pitching the nose down may reduce G. A noticable reduction in G unloads the wing even faster than reducing its AoA, though the effect is temporary, and not as pronounced as having the wing at an appropriate AoA for the other flying conditions.
.
At the point of stall, what is the point of trying to use aileron to pick up a dropped wing?
It's probably dropped because it has reached the stall..

Agreed. It is not vital to have the wings level during the stall, or recovery, though close to level (within 30 degrees, per the certification standard) is nice. Thus, yes, unstall it first and worry about the perfection of other axis afterword.

So,the last thing you would want to do, is to increase that wing's A of A by putting down its aileron....

If the part of the wing with the aileron attached is not stalled, it can withstand a small increase in AoA, if that increase is done with care, and has benefits which outweigh the risks - like preventing a spin entry

Works for me in my Chippy, Tiger Moth

This is of interest to me. I have never flown a Chipmunk, but I did have occasion to check myself out in a Tiger Moth last December. The only pilot around with any experience in them was not able to fly. I noticed during my control check that the up going aileron goes much further up than the down going aileron goes down. would this be an early attempt improving very slow speed handling? Or is it just to keep the low aileron from dragging on the ground? I gently stalled the Moth, and found it responded very nicely to normal use of the controls, though I admit that I did not do any more abusive stalls, as it was really only a maintenance test flight over the airport.

Go speak to your instructor and heed the advice

Well, when this subject came up last time, I did. My local instructor told me that she was taught, and teaches, normal use of all of the controls, and ball in the middle all the time in stalls. My retired test pilot mentor told me normal use of the controls.

Though I hear the "rudder only" technique mentioned, I cannot find any authoritative document where it is a written procedure for a GA aircraft. A friend told me that it is for an F-4 Phantom jet, but I think that's not in the realm of this discussion!

[fireflybob]

Move the control column (centrally) forward until the stall symptoms cease.

The symptoms of the "full" stall are (in any order) nose pitching down, heavy buffet (ok depends on type), aircraft descending and/or wing drop.

The aircraft may be stalled when diving vertically towards the ground - it will still be necessary to move the control column forward to unstall the wing - an aircraft can stall at any attitude or airspeed.

[mad_jock]

Yep Whopity.

The students don't have a chance in hell.

BUt somehow its not considered as being a safety issue.

But the paper work must be correct.

[hugh flung_dung]

I noticed during my control check that the up going aileron goes much further up than the down going aileron goes down. would this be an early attempt improving very slow speed handling? Or is it just to keep the low aileron from dragging on the ground? - didn't you learn about differential ailerons during your PPL training?

Whopity: agreed! :(

HFD

[Pilot DAR]

didn't you learn about differential ailerons during your PPL training?

Oh yes (though PPL training was 36 years ago).

Having flown only a few hours in a Moth, and that 33 years ago, I thought it prudent to stop, and assure that that aircraft (which itself, had not flown in 7 years) was indeed operating as intended. I would look foolish being airborne with a flight control defect, which I had observed on the ground, and done nothing to reconcile before takeoff!

This Moth does not seem to have a flight manual to describe the systems..............