Stall Training

[cessna l plate]

H Guys.
I'm looking for some ideas.

Put simply, I hate stall training with a PASSION!!!!!!!!!!.

I am learning in a C150, and every time we cannot get into the circuit for whatever reason, my instructor insists on going doing some stall training.

I appreciate that this is a neccessary evil of pilot training, and I can handle a standard stall quite well, but as soon as we get into wing-drop, so do my guts. I panic and generally do something pro-spin.

Whilst I can actually recover the aircraft safely, I still hate the topic. Is there some advice as to how to overcome this.
I doubt that I will ever fall in love with the exercise, but if I could be a little less frightened, and at least tolerate it, that would be an improvment.

Thanks

[FlyingForFun]

Have you considered doing some spin training?

I would imagine you would find the first two or three spins quite scary, but you would soon get used to the sensations. You quite probably would never actually come to like spinning, but it would show you that a wing drop really is nothing to be scared of, and that it can be controlled and recovered easilly.

Good luck!

FFF
-----------

[oscarmike]

I quite agree.

I had a very similar experience. I had, of course, read the Flight Training book section on stall recovery before I actually had to do it for real, and thought I had it firmly fixed that, if a wing dropped, you corrected it with opposite rudder.

However, when I did my first stall training (I had only done around 8 hours) and the left wing dropped, in the heat of the moment I inadvertantly gave it full left rudder, with very alarming results! Chart and kneeboard were floating in thin air around the cockpit, and the accelerometer registered -2g! Needless to say the instructor recovered us from the spin.

In short it scared the s**t out of me, and from that day to this, I STILL hate doing stalls.

I've had my PPL for just over two years now, but the need to do stall recovery doesn't go away. With each new type I have flown, stall recovery seems to be a standard part of type training.

So, be assured you are certainly not alone, and just stick with it.

Good luck!

[Genghis the Engineer]

Yes, when you first meet it the stall is scary. But, there are two things that you need to be clear about - one is that properly understood and handled it's a perfectly benign and friendly manoeuvre, the other is that mishandled, especially at low-level it can kill you.

To guard against the latter, you need to be comfortable taking the aeroplane routinely to the point of stall and back again - and the only way to do that, in my opinion, is by practicing over and over again until you do just regard it as a friendly and benign part of flying.

You're obviously early in your studies, which means that you are still flying for the moment with an instructor who is hopefully entirely comfortable stalling or even spinning. So, I'd suggest talking to them, and maybe asking to start by their demonstrating a variety of stalls and recoveries to you - wings level, turning, accelerated, power-off, power-on. Also deep stall (pretty painless in a Cessna) and incipient spin and recovery (less so, but they recover consistently so you've nothing to lose but your lunch). Get comfortable as a spectator, then start to come back on the controls from a position of relative comfort with the manoeuvre, and under the competent supervision of your FI.

And please trust me on this - there are people like me who do hundreds of stalls in prototype aeroplanes, tweaking the design if necessary, scaring ourselves silly on occasion, to ensure that what YOU get to fly is sufficiently benign that the stall is really a non-event, AND that the stall warning is clear and timely. You just need to learn to feel familiar low speed handling, leading to the stall, leading to the recovery, with lots and lots of practice.

G

[Dewdrop]

Talking about upper air work, the one I didn't like, mainly because it just felt wrong to me at the time was steep turns. Holding the extra G for 360 degrees just made me feel uncomfortable. I suppose though as with stalls we need to keep in mind it could save our lives one day. I trained in a C172 and never actually got a wing drop but I can imagine its scarey.

[Tinstaafl]

If they're bothering you that much, perhaps stepping back from them a bit followed by a gradual re-introduction will help you.

Tell you instructor about your difficulty & ask if you can do a period of slow flight ~5-10 kts above the stall. Get used to flying around at this speed in different flap configurations. You'll need to add power during turns.

Once you're quite comfy with this fly with the stall warning just activating. Get used to stopping it by reducing AoA, starting it by slightly increasing AoA. Again, you'll need to coordinate power during manoeuvring. Focus also on being able to maintain a heading with wings level ie use rudder to PREVENT yaw away from the desired heading. Use a distant surface feature as an aim point.

Next step is to take it to a power OFF stall in straight, unaccelerated flight. Just like in the previous exercise, stop the stall by reducing AoA. The goal is for you to CONTROL the process. You could, for example, stop the stall just enough to leave the stall warning activated, or recover to a slow glide. Don't forget the wings level/no yaw thing. After getting comfortable with flap up stalls, progress to increasing flap settings.

Next is to stay in the stall for a period while still holding the heading. Recover after a while eg500' height loss. Ditto the flap settings.

Now do a straight stall, recover and use power to minimise the altitude loss. Don't rush the recover at first. Take you time to transition through all the previous stages you've been practicing. Add power after the stall warning stops. Start adding power earlier & earlier until you are comfortable doing this pretty much simultaneously with the other recovery actions. Ditto the flap settings.

Next is power on stalls. Start with minimal power, building up to climbing stalls.

Do the same process with turning stalls. Start with power off, shallow AoB. Build up to increasing power & bank angles.

Depending on the a/c type some combinations of flap/power/turns will cause more abrupt stall behaviour than others. The goal is to leave those ones until the very end of this process. Your instructor will know which combinations are more benign & these are the ones to do first eg it might be that stalls up to 20 or 30 deg AoB are more benign than climbing stalls. Fine, do those before climbing stalls etc.

[Dop]

Dewdrop, the weird thing about doing steep turns was that when the instructor was showing me I started to feel a bit queasy after a few turns.

Then when I did it, I felt fine!

[strafer]

CLP,

Pretty much everything I was going to say has already been said. I will add though, that I too hated my initial stall training. What made the difference was when I realised why we were doing it and what we were trying to simulate. There may well come a time (even a few hundred hours from now) when you're out solo, you turn final, you haven't been keeping an eye on the ASI BUT you react immediately to that buzzer/buffet and recover your a/c without inserting into someone else's chimney. The training you're doing now could well save your life later down the line, and although your reactions are the wrong ones at the moment, they will come right.

As I said, like you I hated doing stall training during my first few hours, now I try to do some every time I go up and I actually enjoy it.

Keep at it,
Strafer

[noisy]

I have recently done some stalling for the first time and I didn't enjoy it much. I find in the C152 that almost all forward vision is lost and that this is deeply disconcerting. However, there is no particular sensation of falling. I am just very happy when the time comes to relax on the yoke and get the power in.

I also found out the hard way not to use aileron in the stall. This was also rather unsettling and I felt sick for the rest of the day even though I retained my breakfast. As a consequence, during the stall I recite

"I must not use ailerons"
"I must not use ailerons"
"I must NOT use ailerons"...

[Kirstey]

Small Tangent!

I recently did some stalling in a Terrorhawk. Wing dropped like a git everytime. I have to say I loved it after the 1st one! and went up on my own thenext week to make sure I was comfortable. However I was told the wong drop recovery was Basically the SSR only correcting the wing drop after the aircraft was unstalled (with aileron) now I always read that the wing drop had to at least be stopped with opp rudder.

any comments?

[down&out]

I think allot of good advice has already been given.

From my experiences, I would say, once you have had a bit of time after getting your PPL, if you are still uncomfortable with stalls/ steep turns, book a few aeros lessons. You find them great fun and then stalls and steep turns will feel very tame!

Also Dop, its a very common occurrence that when you are actually flying you don't feel ill!

[Tiger_ Moth]

I don't like stall training either, but I don't like it because it's so boring and there isn't much to it. I don't find it scary at all. Spinning however is great fun, I love to spin and anybody who hasn't is missing out.

[englishal]

Why not try stalling another aircraft to get your confidence up? If you stall say a PA28, you'll find that the stall characteristics are completely different to a Cessna. The cessna likes to drop a wing, the PA28's don't. You can hold a PA28 fully stalled for 20 seconds easily (altitude permitting of course :D) just using small rudder inputs to remain level.

As you progress through flight training, you find that "normal" intentional stalls are nothing to worry about, if you're with an instructor and you spin, he/she will recover. If you can't see forward look at the wingtip, this will tell you pitch,yaw and roll, and you'll feel the buffet. As long as you're co-ordinated and don't use the aeilerons you'll be fine, if a wing drops, rather than trying to pick the wing up with the rudder, recover from the stall then pick the wing up. Use rudder to remain coordinated during the manouvre and it is unlikely a wing will drop too drastically.

Good luck
EA

[HelenD]

I was OK with stalling in the PA28, I could even tell when the wing would drop because the instructor had to stick some rudder in. I did have trouble pulling back enough to get it to stall. All this changed wheen I went on to the PA38, I was not prepared for the vicious wing drop and got quite worries as not long after the wing dropped the nose dropped and I thought I would spin. The books made the spin sound scary. Just before my test I was taught how not to get the wing to drop in the stall this made me less apprehensive. A few months after my test I got my PA38 instructor to demo a spin - it was no where near as bad as I imagined it would be. I will always be wary of the stall and try to recover at first sign.

[Tinstaafl]

I disagree with the idea that one should use rudder to prevent wing drop &/or raise the wing. My 'take' is that rudder should be used sufficiently to stop the yaw. Raise the wing using coordinated aileron/rudder once unstalled.

[M14P]

Only use rudder to 'prevent any further yaw'. This is really rather transient since once the wings are flying fully again the yaw will stop. Use aileron to roll wings level during the recovery.

Picking up the wing with rudder is at least as dangerous as using aileron in the stall (modern aircraft are certificated to withstand a great deal of aileron mishandling during the stall) - think about it; aircraft stalled and significant rudder = pro-spin control.

Perhaps your instructor is insisting on heaving the aircraft into a stall? Why not try very slow decelerations (less than 1knot/sec) the value is in watching the stall develop.

My view is that if you are not happy with stalling you will be flying unhappy with a very significant area of aircraft behaviour - it will affect your landings since you will petrified of the stall (and it's proximity!)

[Wee Weasley Welshman]

Use rudder to prevent further yaw.

Stall training is a bit of a chore or a bit of an excuse for some fun depending on your temperment.

Just be frank with your instructor and he will accomodate your discomfort.

Good luck,

WWW

[noisy]

My instructor tells me that the aim of the exercise is to deep stall the aircraft and prevent a wing from dropping using the rudder. Maybe the aim of the exercise is just general airmanship.

Another exercise is the stall during the turning descent. Two stages of flap, moderate bank and pull to the stall warner. Apply full power and level the wings with opposite rudder.

Then of course there is the straightforward incipient recovery.

I have troble with the rudders: I'm not much of a dancer :O

I don't see much value in looking at the wingtip during the stall; True you will get a good appreciation of movement about all three axes, but personally I can't help then correcting with aileron.

[M14P]

Noisy - a deep stall is something quite different from a full stall. If your instructor is talking about deep stalling I suspect him or her to be a little unsure of the difference (your still here so I assume you've not been deep stalling for real!)

The aim of the exercise is to learn the characteristics of a fully developed stall and to learn the recovery actions.

A further learning point is to recognise and recover from the onset of a stall.

To prevent wing drop with rudder is a rather dangerous way to expain what you are dealing with. Completely preventing a wing drop is exactly the same as picking a wing up with rudder - any yaw that develops will effectively be pro-spin.

It is much better to think of the phrase 'prevent further yaw' because without yaw the tendency to spin is very much reduced. Preventing a wing drop assumes that your rudder is powerful enough to overcome any autorotative tendencies right down to speeds below the stall - which it might be on the type you are flying now but might not be on the next type.

The aim of every exercise is to build airmanship. You must understand stalling but I feel that it is covered very badly indeed. All of the time is spent some way above the stall talking about 'sloppy control response' etc (which I think is very difficult to prove in some training types) then one rapidly decelerates into a hoofing great stall with a frantically pattering instructor trying to mention all of the salient features.

Very little time is spent around the high drag/high sink area close to the stall examining the fact that many training aircraft have comparitively little buffet as an onset warning. Very little is made of how one can spend time - at height - examining how quickly and delicately one can break a stall.

I feel that it is very poorly covered and we now see instructors who have a fear of stalling and a terrible understanding of the behaviour of an aircraft near the stall. The message is very much that there is stalling or flying and nothing exists in between. That, of course, encourages the view that stalling is a killer around the corner that will occur in the blink of an eye.

[shortstripper]

Hi All,

Coming from the gliding world to power I have never found stalling, spinning or slow flight anything but normal. True, it is easy to recover far quicker in a relatively benign glider, but scratching for lift at high bank angles and nibbleing the stall really does teach "feel". Often, and this applies to power also, a firm quick push will get a wing to "bite" again with virtually no loss of height. Even with huge glider wings, rudder wasn't used at the incipent stage and the exercise was simply to recover by elevator then use co-ordinated rudder and aileron once unstalled. As has been pointed out rudder is used to counter excess yaw only as too much could easily flick you into a spin in the opposite direction. In a fully developed spin, full opposite rudder is probably only applied for a split second to speed yaw correction before it is eased off, but this becomes too instinctive to easily analysis.

Very slow flight, especially at or just into a stalled condition is often not taught at all. As I'm not an instructor I don't know what the patter is or whether it is actually required to be taught. In my experience it seems to be glossed over in the power flying world, which is a great shame. Some instructors seem to think that the only way to teach a pupil about stalling is to plough straight into a fully developed one straight away and forget that what seems gentle to them is often traumatising to a pupil. Stalls, and IMHO spinning should hold no fear and correct recovery should be instinctive not something to require thought at the time. The only way to achieve this is to allay any fear and discomfort, and the only way to achieve that is sympathetic instruction and practice.

IM

[noisy]

Hi M14P,

Sorry, it’s just my terminology. The ‘deepest’ stall I have done is one where the forward component of speed is very low and the nose wanders around quite a bit and wallows. The yoke must be held all the way back. In this situation it appears that the wings can be kept level by a small rudder input, but the aircraft continues to yaw. Or so it seems from the DI rotating. I certainly wouldn’t condone the abuse of rudder at low speeds or in the stall.

The baby Cessna is a very well engineered and forgiving aircraft, but as you rightly point out the controls of this aircraft are very effective throughout the speed range and sloppiness of the controls can’t really be demonstrated. There is no buffet.
I wonder if there are any trainers in which these effects can be demonstrated?

Noisy

PS my instructor is a farm strip pilot of advancing years who I trust. Obviously this student needs to do some more study!

[M14P]

No apology needed - just making sure you weren't being led astray. That is about as fully developed as your Cessna might get. It is interesting to fly something that will stall without the stick in your stomach - Bulldog, Chippy, FLS Sprint, anything sufficiently 'British' as to behave classically.

Your DI might be precessing due to low vac pressure - look at a feature on the horizon!

I agree with Shortstripper - why not ask if you can try flying around just a knot or two above the stall. It's a real coordination exercise and needs plenty of power to keep things going. Generally, however, I find it a real confidence booster for students. It's also good for explaining the use of rudder for coordination - turning left, large right rudder input for coordination etc.

[noisy]

Yes, I've done slow flying and it's a pain in the :mad: flying around with the stall warner briefly sounding all of the time. It is part of the syllabus. Very hard work. I think I will try out a few different types after I have got my PPL, all being well.
There is a Chippy at the airfield I fly from. Hmmmm. :D

Not sure about that DI: I will have to go away and have a think about it, although my senses were also telling me that the a/c was gently turning.

[IO540]

May I ask what might be a stupid question: what is the point of flying for ages doing stalls, or flying around at just above the stall?

Aerobatics aside, every PPL should be taught how to recover from a stall, and the reaction (controls forward without additional roll input, full power) should be instinctive upon the stall warner going off. But why do so apparently much of it? During normal operations of a plane, the only place one is likely to stall is on turn base to final and then you are likely to be too low to do anything about it anyway (unless you are doing it 5 miles out :O )

In most cases of an inadvertent stall, the plane has been grossly out of trim and the pilot wasn't paying attention to the IAS. Teaching trimming is far more important.

I may have mis-understood, but it seems to me that some instructors have got their hands on a WW1 Luftwaffe training manual and really enjoy it. A bit like the IMC Rating instructor teaching you NDB holds to near perfection, for hour after hour, having planned the headings on the ground from winds-aloft forecasts of course..........

[noisy]

I believe that the whole point of the slow flight element is a sort of what-not-to-do. Except that you're ...er.. doing it.

[M14P]

IO-540

I feel that you are missing the point a bit: The whole point is to teach delicacy of handling, technique and to instill confidence in the student.

Trimming, on the other hand, is very poorly taught but has never been a big issue when it comes to stalling. An aircraft can stall whether it is in or out of trim; your assertion that 'in most cases the aircraft was grossly out of trim' is pure conjecture and more than a little silly.

Take for example a stall spin accident where a chap was circling a friends house and pulling ever harder as the speed decayed/ AoA increased etc... would the outcome have been any different had the stick force been less?

Similarly a recent report included a stall/wing drop whilst the pilot struggled to close the door...

How often do you fly within 10 kts of the stall? Every flight I'd suggest - at take off and during landing. I'm fairly sure that an absolute terror of stalling is at least partially behind many landing accidents i.e. excess speed on final and/or snapping the nosewheel off.

Why bother being taught how to force land? Engine failures are rare so why not just accept a certain rate of fatalities!?

Why bother being taught a lookout since the aircraft you collide with is likely to be the one you don't see!?

Part of the fun of flying is developing a discipline - stall avoidance and aircraft control are components of that.

[IO540]

M14P

Trimming, on the other hand, is very poorly taught but has never been a big issue when it comes to stalling. An aircraft can stall whether it is in or out of trim; your assertion that 'in most cases the aircraft was grossly out of trim' is pure conjecture and more than a little silly.

I would suggest that (stupid behaviour aside, like the cowboy circling a house with an excessive bank angle) most stalls are the result of

1) the aircraft being trimmed to a low speed, and the pilot becoming distracted, and the IAS decaying, or

2) the pilot flying say 10kt above Vs and then banking hard (e.g. a very hard base to final turn)

In neither case above is low speed flying going to help. One must do an immediate stall recovery.

In your example of a pilot trying to close a door, if the plane was trimmed anywhere near right, it would not have stalled hand-off. Like every plane, it would eventually have gone into a spiral dive, but that takes one back to flying the plane first and fixing open doors (or attending to distressed passengers, etc etc) separately - stall training is of no help if you are trying to close a door and forget to fly the plane.

Flying 10kt above Vs is perfectly safe so long as you are trimmed, are wings level, or bank below say 20 degrees. But one will be doing that in so few places (initial climb, or base/final) that in my view it would be better to teach the procedures (e.g. TRIM TO 80KT ON BASE LEG).

My question was not whether to do stall training, but whether to do so much of it. I must have done 3 hours of it myself. It was great fun but mostly irrelevant to normal aircraft operation.

Your examples of forced landings and lookout are not applicable.

[Arclite01]

I'm no expert but I have found that talking through what you are doing out loud seems to help because you understand what is happening, you can help yourself through the signs of the approaching stall, the symptoms of the stall itself (including wing drop) and the recovery.

In addition it lets your instructor know your thought processes are sound, and helps your confidence no end.

It works for circuit planning too !!

Some people never like stalling but once you've done a load they become just another part of flying.

Please don't be put off by 1 unpleasant element of flying, - and something else which has occurred to me - maybe another instructor might teach it differently so just for this exercise maybe another instructor might be useful ?

cheers

Arc

[M14P]

540

I simply do not agree with your assertions. Stall and spin awareness will remain central to fully understanding the behaviour of the wing in the low speed regime.

More to the point - stalling is required to pass the skills test

Also - bank angle alone has no direct effect on stall speed - only AoA so if you start all of this keep less than 20 deg here nonsense you are leading yourself into an area of false confidence and understanding.

It's quite clear that you are a 'numbers man' which has its place but it strikes me that the original poster is not 'in that market'.

Back to enjoying the whole experience and being confident; might I suggest some well flown demos by your instructor should help restore some confidence (if that's what is lacking).

[Gertrude the Wombat]

During normal operations of a plane, the only place one is likely to stall is on turn base to final and then you are likely to be too low to do anything about it anyway Um, no, I don't think so. I think that part of the point of the stall training is so that you can recover easily with that amount of height.

Most people turn final hundreds of feet above the ground. You shouldn't need that much height to recover from a stall.

[shortstripper]

1040

I'm sorry but I think you really are a bit naive if you think that three hours of stall awarness covers everything to the point of boredom. Forget IAS, it's fairly irrellavent and should be treated as no more than I guide. AoA is the main factor closely followed by flying in balance. Well flown tight turns even on base are safe if you have the skill and finesse to fly them well. Far more dangerous is the fool who believes too much bank is unsafe and tries to rudder it around:ooh:

My point about plenty of slow flight and stall practice is that you learn how to recognise the onset of a stall, feel comfortable with it and even use it to your advantage. Many glider pilots scratching for lift low down will appreciate that to stay within the core of some weak thermal will require a very tight turn at a very low speed. Anything more than the very smallest radius of turn will result in a landing so you soon learn to fly on the very edge of the stall. Indeed this all becomes a personal challenge and deeply rewarding when you succeed in getting back up when others would have simply thrown it away and landed out. How does this relate to power flying? simple, it is one more skill to be mastered and is one that could ultimately save your bacon. I won't offer scenarios because you'll just say "only a fool would have got into that position in the first place" ... this may be true, but it happens. After all, to become experienced, requires experiences ... we just hope our training and our own personal standards are enough to get us through them.

IM

[Genghis the Engineer]

Yes.

I'm not sure when you can start to feel you fully understand the stall. Without going through my logbook with a calculator, I must have done somewhere around 100hrs of stalling and spinning and am not even close yet.

But, probably closer than I was with 3 hours, and certainly closer than I was when I managed an inadvertent spin when I only had probably about 200hrs TT in my logbook some years ago (thankfully at a very safe height).

G

[IO540]

You people are right that I am more of a numbers man that some, perhaps. I do like to fly around here and there and do so quite often, just for currency. But most of the time I like to plan a flight, takeoff, fly it (IFR/VFR as necessary) and land, and do so very safely without ever getting anywhere near doing anything dangerous. Never getting anywhere near the stall, for sure. I fly downwind at 100kt (25kt above stall), base at 85-90kt (15-20kt above stall at that config), final at 75-80kt (15-20kt above stall in that config), flare at 70-75kt and that does me just fine.

I am aware that bank angle itself does not raise the stall speed, but that's true only in a 1g descending turn - perhaps true on base to final. If you do a level turn then Vs does go up because the AoA has to increase to support the extra G.

I used to enjoy deep stalls in a PA38 - beats the best fairbround ride. But then it ought to, at £100/hour. The instructor loved it. At the end of all this you get a PPL with which the average pilot cannot navigate accurately enough around UK's busy airspace!

[shortstripper]

I don't know where this "deep stall" thing is coming from? A deep stall is one in which the elevator is directly blanketed by disrupted air from the stalled wing. This means it becomes ineffective and you can't fly out of the stall as you effectively have no elevator.

I think you mean fully developed stall or perhaps an abrupt stall with a good break.

Flying as you describe is fine and obviously works for you. I don't knock you for that. It's fine If you are only flying from larger airfields and never expect to either force land or use small airstrips. Apart from not getting into a field if flying too fast for fear of stalling, I just think that one day if your luck runs out ... an inadvertant stall might just sneak up and bite you on the bum!
Of course we all fly to a greater or lesser degree on good luck ... I just prefer to have a bit of extra tucked away to give luck a hand :ok:

On the original theme of this thread I would just recommend that if someone feels uncomfortable about stalling, they shouldn't just go through the motions, move on and only re-discover stalling by accident!

IM

[RodgerF]

Another point about slow flight is that it provides experience in flying the aircraft at the back of the drag curve, when counter-intuitive effects need demonstration. (you need more power to fly more slowly straight and level). Landing itself is a slow flight activity.

So many PPLs have lost touch with these skills, I find PPLs uneasy at slowing down to 50-55 kts for a performance landing in a 152 for example. The pernicious effect is to develop PPLs who approach far too fast and wonder why their wonderplane floats for ever, or alternatively say 'It needs flying on to the runway'. Where is the lost art of holding off? Cessna 172 drivers flying approaches at 75-80 kts when 60 would be more appropriate.

[M14P]

540

I think the message here is that just because you think you've done enough of a certain aspect of training doesn't mean that you know it all.

Obviously you enjoy flying your Saratoga, Lance, Commander, Viking or Comanche (I assume that's what you own) and using it for the purpose that it is designed for. You've rather lost sight, however, of what training is all about. It is about learning and development - it's also about equipping a student with skills needed to cover a broad range of flying.

It's been said before - a PPL is a license to learn. Are you still learning? Are you still receptive to input from others? What makes you think that in 3 hours you have the answer to stall/slow flight awareness training? You wondered if you were asking a stupid question - well no, you are not. There are no stupid questions apart from those that are never asked! You just didn't seem to want to hear any answers.

RogerF gets where I'm coming from too (I think!)

Next time you need your 'flight with an instructor' drop me a line and I'll be pleased to spend a day with you. I guarantee you'll learn something (even if it's just that you don't like me!) and I am certain that your views will change.

Like Genghis I probably have more than a couple of hundred hours spent stalling and at the back side of the drag curve. I would love to share some of what I've learnt with others.

[strafer]

If you're really worried, for less than $900, you can have one of these:

http://www.angle-of-attack.com/Default.htm

[Genghis the Engineer]

I'm not a QFI, but I do occasionally help teach groundschool on a course for baby test pilots. I've posted below some notes from that course which might be of interest.

All is (c) Genghis, but by all means any instructor who can make use of this feel free to copy it and make appropriate us. One of these days I'll find the time to put all this together and publish a book, but I'm far too damned busy at the moment.

There are some tables that normally go in this text, but they're only really relevant to test pilots, and anyway I don't know how to post a table in Pprunetext.

G





The Unaccelerated and turning flight stalls

The unaccelerated stall is very important to the airworthiness of a fixed wing aeroplane in a number of ways. It is essential to the definition of many of the critical operating speeds - the approach speed and Va in particular are functions of the stall speed. It also defines the manoeuvre margins for a turning aeroplane, and for most light aircraft codes, decide whether the code may be applied at all, particularly for microlights.

The conduct of stalling tests on a new or significantly changed aeroplane is a potentially hazardous business, and flight testing practices is a whole separate subject; however, the references cover this in good detail. There are however a number of points pertinent to the testing which are not always well understood, and are worth repeating here: -

· The stall is entered at flight idle, at (by convention) a deceleration rate not exceeding 1 kn/s from a trimmed speed of around 1.4 Vs..
· It is impossible in all but some gliders to conduct a stalling test in level flight, the aircraft will be descending.
· No two aircraft types will give identical stall or warning, it is important that the characteristics for the type and variant is identified, repeatable, and documented in the pilots handbook. Many airworthiness standards give overly simplistic definitions of the stall, which may or may not reflect what actually happens - be guided by these, but not bound by them.
· Stall speed data is meaningless from an airworthiness perspective without the ASI having been calibrated .
· Stalling characteristics will vary with CG and power setting. With CG expect to see higher stall speeds at fwd CG, and more dramatic post-stall behaviour at aft CG. With increased power settings, stalling speeds are likely to be lower with more nose-up stalling attitudes. Increased power again, is likely to generate more dramatic post-stall behaviour; some aircraft which are extremely benign when stalled at idle power will tend to enter immediate incipient spin (sometimes with no stall warning) when stalled at high power settings (two examples of the latter characteristic are the UK air cadet variant of the Grob G109b motor-glider, and the Ultraflight Spectrum microlight).
· The stall is not necessarily marked by the classical pitch-break beloved of flying instructors. It may be marked by a loss of nose-up authority (most microlights), an AoA triggered Klaxon (the Aviasud Mistral), an air horn supplied by air pressure from the wing under-surface (Cessna 150), or other cues. The bottom line is that the stall occurs when the pilot ceases to have absolute control over the aircraft - but learn and understand the precise definition used by the standard in use. Equally, ensure that the test pilot, flight test engineer, and airworthiness engineer are all in complete agreement as to the stall definition in use for a test programme, and subsequent documentation.
· Wing-drop at the stall is normal to most aircraft, it is the magnitude of it that is critical to airworthiness. The wing drop limits of all standards assume that correct recovery action is being taken.

The turning flight stall

For the purposes of civil certification, the turning flight stall is universally carried out at 30° of bank in a co-ordinated turn, although requirements for power and flap settings may vary. Since this is an unaccelerated stall, again the entry rate will be no greater than 1 kn/s.

It is almost inevitable that any aircraft will suffer from undemanded rolling at the point of stall, and this is generally more marked in a turning flight stall. There is no universal value which dictates the acceptable limits of this, and it is important to be aware of what the relevant standard says. The terminology universally used for this undemanded rolling motion is “into the turn” and “out of the turn”. If an aircraft is banked to the right, and at the point of stall it banks more to the right, then it is said to have rolled “into the turn” (this incidentally is a characteristic most commonly associated with low wing aircraft), whereas if it tends to roll towards wings level (a characteristic most often found in high wing aircraft) then it is said to have rolled “out of the turn”.

Regardless of the precise wording of any requirement, it is important that stalling from a co-ordinated turn cannot cause a spin. The author has seen several aircraft which did display this tendency (i.e. never assume that it won’t be there!), the best known of which is the North American Harvard which routinely will enter an incipient spin from a stall at PLF or MCP - a characteristic which is believed to have killed a good many student pilots during WW2. Similarly any marked pitch-up or control force lightening at or near to the stall should be regarded as unacceptable.


Recovery from the unaccelerated stall

Most aircraft will pitch down, with varying degrees of severity, at the point of stall. This naturally puts the aircraft into a dive from which the existing trim setting should allow it to recover without pilot input - although for an efficient (and comfortable) recovery correct handling by the pilot - initially to allow the aircraft to recover flying speed, then to pull out of the dive and re-establish straight and level flight (probably with an increase in power) is considered normal.

However, it is important (and some standards, although not all do discuss this) to ensure that the acceleration immediately following the stall cannot lead to an inadvertent exceedence of Vne / Vmo / Mmo. Also the pullout (especially that pull-out naturally caused by the pitch trimmer setting) must not cause the normal acceleration or Angle of Attack limits to be exceeded.



The accelerated or dynamic stall

Whilst for the purposes of determining stalling speeds a 1 kn/s deceleration is universally used, this is not necessarily appropriate to every real-world situation. Indeed, most microlights will have some difficulty in entering a stall at only 1 kn/s. For this reason, most standards also require consideration of a more rapid stall entry, either from a rapid wings-level pitch-up, or from a steep turn. The specific requirements of each standard do however vary considerably; this is unsurprising since in the more coarse manoeuvres, the different weight-classes of aircraft inevitably will be flown in very different ways.

How aircraft behave in response to this is very variable. Most aeroplanes will display a more marked nose-down pitching motion (or a measurable one, if none existed before) at the point of stall. Aeroplanes with laminar flow lifting surfaces are likely to display less wing-drop at the stall (because both wings stall at the same time), whilst aeroplanes with more conventional wing surfaces are likely to display more wing drop. Some high wing aeroplanes, when stalled from a steep turn will tend to roll naturally wings-level before naturally resuming straight and level flight (probably as the wings stall, pendular stability becomes the dominant roll effect).

The following table shows the main requirements of the various standards. The reader should however treat this with caution - all the standards are somewhat vague (and often probably too relaxed) in their requirements, and it is most important to construct tests which reflect the way in which the aircraft will actually be flown. Most organisations dealing routinely with flight testing (particularly those dealing with the lighter end of aircraft certification) will almost certainly have their own type or class specific schedules and guidance which should also be referred to - and may well be much more useful than the main certification standard.

This table doesn’t give much information on test conditions. Unless stated otherwise, test conditions are the same as for 30° turning flight stalls discussed above.

The stall warning margin in a dynamic stall

For all the listed standards, stall warning requirements are the same as for the unaccelerated stall. Whilst at first glance this is entirely sensible, in practice it is not and the sensible airworthiness team will aim to go beyond the minima of the standards.

Consider for an example, JAR-23. JAR -23 has a requirement for a minimum 5 knot stall warning margin, and a test deceleration speed for the dynamic stall of 3-5 knots per second. This potentially would give a pilot as little as 1 seconds warning of the impending stall - only enough for the most alert pilot (in an aircraft high elevator power and a very short SPO) to take appropriate action. For any aircraft that is likely to be routinely flown in violent turning manoeuvres (e.g. aerobatic aircraft, utility aircraft used for short field or agricultural operations, any military aircraft or most training aircraft) it is important that the pilot is given clear and unambiguous warning of the impending dynamic stall. Apart from the obvious artificial stall warning devices, ways in which this might be achieved include high stick forces, very high nose-up pitch attitudes, alarms triggered by AoA sensors.

Going beyond the minima of the airworthiness standard in this way can require some courage, particularly if potentially expensive modifications to the aircraft may be required. However, any recent set of fatal accident reports should furnish one or two cases of aircraft loss due to a pilots failure to recognise the dynamic stall - this and the risk of litigation is generally sufficient to convince the most bloodyminded company accountant.

References
- Flying Qualities and Flight Testing of the Aeroplane, Darrol Stinton
- Flight Testing Homebuilt Aircraft, Vaughan Askew
- Flight Test Guide for Normal, Utility and Acrobatic Category Airplanes, FAA, AC23-8

[IO540]

shortstripper

Yes sorry I meant an abrupt stall; a PA38 usually drops a wing pretty quickly.

Re forced landings or short strips: I actually use the POH figures and config; I am not adding 10kt or whatever for good measure. With a Vs of 59kt, 70-75kt on final when starting the flare is fine. I know some people say that a landing should be a full stall, with the horn going off, nose way up etc but I don't go for that; for a start you don't get much rudder authority.

It is easy to land in a distance which one can never takeoff from later. Isn't that true for any aircraft? It certainly is for mine.

RogerF

I do know about the back of the curve, believe me. All I have to do to get there is fly at 18"/2300 (the normal approach config) and drop the gear while forgetting to put some power back on (20"+) right away. Another way to get a nice suprise (especially nice if in IMC) it is to descend on autopilot in VS hold mode with less than 18" MP (very tempting if gear isn't down) and not put power back on when the AP reaches the preset ALT and levels off :O

Recovery from the above, if needed while maintaining altitude, needs a lot of power applied right away. But I wouldn't choose to fly on the back of the curve deliberately... there isn't any point. Engine cooling is one reason.

M14P

I do learn something on every flight. The 45-hr PPL is indeed a "license to learn". I suppose I got into this thread because someone seemed to be doing a lot of this.

It is a pet subject of mine; the way the PPL includes a lot of this sort of thing while leaving out the stuff which is just as essential if somebody wants to actually fly anywhere afterwards. This situation is understandable given that nearly all PPLs chuck it in shortly afterwards (maybe this is one reason why they do?) so there is no pressure on schools to turn out pilots who can confidently go places. But I won't say any more on this.

[FlyingForFun]

It is easy to land in a distance which one can never takeoff from later. Isn't that true for any aircraft? It certainly is for mineCertainly isn't the case for mine :p ;)

FFF
---------------

[Lowtimer]

It is easy to land in a distance which one can never takeoff from later. Isn't that true for any aircraft?
Only some. Agreed, in a type with low power-to-weight ratio, the landing might be quite short but the take-off much longer, I often find this to be the case in the 90 hp Super Cub two-up. But with more power-to-weight ratio, the balance moves the other way. It is very rare for me to get the Yak-52 down and stopped icomfortably using 300 metres of runway. In still air I'd think I was doing OK using 400 metres. (Perhaps I'm a rotten pilot, I accept the possibility.) I usually get off the ground in much less. Slope plays a role too. If you're operating downhill, you can take ages to stop but leap almost straight off the ground on departure. Uphill it works the other way.

But I wouldn't choose to fly on the back of the curve deliberately... there isn't any point.

I don't know what type you're flying and probably haven't flown one, but a lot depends on individual types here too. Some aircraft have a very narrow "back of the drag curve" regime. Types with high aspect ratio wings, e.g. gliders and motor gliders, tend to be most efficient pretty close to the stall. They also tend to have effective direct means of steepening the descent, e.g. spoilers or airbrakes. So for those types there's not a lot of scope for exploiting the back of the drag curve. Other things being equal, a lower aspect ratio wing will be more efficient at a higher margin above the stall. So something like a plank-wing Cherokee 180, or indeed the Yak, has a very useful and quite broad flight regime on the back of the drag curve, and exploiting this makes it very much easier to land tidily at a determined touchdown point and stop in a short distance. In the Yak, with gear and flaps down, at 160 kph you are on the front of the drag curve. At you reach 150 you can just feel it settle onto the back, and then you have the ability to make small rapid variations to speed and rate / angle of descent quickly in any desired sense. (Only on a good steep approach though, no "dragging it in"!). It doesn't stall until 100-ish in that configuration so the width of the regime is a lot greater than the few knots you might get in a motor glider.

[M14P]

FFF - I agree, most reasonably powerful aircraft need a little more room to stop than to go but beware sweeping generalisations (eh 540!).

I can usually stop a Bonanza really short mainly due to gear geometry and the way the wing flies on the back side of the drag curve (ok 540 so there is a use). Getting airborne is another matter entirely due to the climb gradient decrement that is unavoidable if one tries a soft field style take off. Not a problem if you have a reasonable climb out area in terms of obstacles. This technique is very useful in cases of rough or very wet fields (not just short places). I find that the 114 is very similar.

Single Comanche or SF260 are the other way around since the geometry and drag characteristics makes this sort of approach impracticable.

In either case proficiency in that regime is needed.

540 can't see the point of any of the above.

540 - I have other ideas about why people give up. Nearly all of it is down to cost and motivation. I think managed groups and a scheme of mentoring would help greatly (I have developed some plans for both) but I agree that the 45hr PPL course casts the average pilot adrift at the end of it.

Bear in mind, however, that not everybodies idea of Valhalla is to be adjusting the V/S control on a mode control panel.

[Bluebeard777]

Maybe some of the stall pundits here can shed light on the following.
My aircraft stalls at 31 mph IAS at max weight, the book figure is 35 mph "in level flight". The ASI has recently been checked and found accurate.

Recently on a near-windless day I thought I would check this against the GPS, out of curiosity. So I went up to altitude (2900 ft density altitude), near max weight and middling CofG, slowed gently and stalled on a downwind heading, then upwind, then 90 deg each side. To my surprise and puzzlement the GPS speed in each case was 54-55 mph with little variation.

I do not know whether the GPS figure will include the vertical speed component, which I reckoned was about 500 fpm (= 6 mph) at the stall.

Has anyone else here tried this?

[Genghis the Engineer]

(1) You were at altitude, and therefore CAS<TAS. The aircraft stalls at a fixed CAS, not at a fixed TAS.

(2) GPS lag - it's not an instantaneous speed device and needs to stabilise for some seconds - something the aeroplane is unlikely to do.

(3) ASIs are calibrated down to 1.3Vs and up to Vne, it's common to get greater than the permitted errors outside that range.

(4) It's common at high AoA for the ASI to significantly underread due to poor flow into the pitot.

(5) You were lighter than MTOW, which is the weight at which Vs is quoted.

(6) GPS only gives groundspeed. Descending at a high RoD you are actually flying rather faster than GPS will give.

(7) You are mixing up knots and mph somewhere along the line.

(#) Any combination of the above.

G

[noisy]

Thanks Genghis, this is all good Gen, particularly (3) & (5)

[M14P]

I agree with all of the above and possibly there may be some excess 'G' involved if you were trying to maintain level flight. A very slow deceleration in a slight descent should ensure that you creep up to Vs under (near as dammit) 1G conditions

[Genghis the Engineer]

If it's (5), the stalling speed you see should be roughly the declared stalling speed x the square root of (Actual weight divided by MTOW).

M14P - increased g should increase the stalling speed, not decrease it. On the other hand, less than 1g during a slightly greater than necessary descent should decrease it.

Another factor I forgot to mention is deceleration rate. The book figure should be for bang-on 1kn/s, a greater deceleration rate should give a lower stall speed, and a higher deceleration rate *may* give a higher stall speed.

G

[M14P]

Genghis

Isn't that what this chap is expressing concern at - an increase in stall speed (31-34 scheduled versus 50-odd observed)?

I always need to descend to achieve 1kt/sec at idle for schedule speed checking.

[Genghis the Engineer]

Ah, but a good test pilot gets lots of data from one test. What I saw in there was:-

- Low apparent stall compared to book figure.
- Large disparity between GPS ground and ASI indicated speeds.
- Apparent lack of difference between GPS groundspeed into and downwind.
- Difference between TAS and GPS groundspeed due to RoD
- Use of non-aeronautical units.

And was trying to cover all of those without getting too complicated and including power and CG.

G

[M14P]

I'm not sure that an IAS was quoted for the GPS based test conditions!

Nice post re stalling - Stintons book is a great source for that sort of stuff. I can commend it to anyone with an interest in testing...

[Bluebeard777]

These are interesting comments.

Ghengis:

(1) TAS v. CAS: Yes, but hardly so as to have such a large difference as I observed?

(2) GPS lag: I did "creep up" slowly on the stall each time. Definitely the stalls were approached at less than 1 kt/sec decrease. GPS speed was observed constantly (by the passenger) and stabilised. I am convinced GPS lag cannot have been a factor, and even if I were wrong, its effect could perhaps be 1 or 2 mph, not 15 or 20.

(3) and (4) Yes the ASI is in an position at stalling AoA which is likely to give inaccurate readings. If one starts from the premise that the GPS does not lie in respect of speed over the ground, then the inaccuracy must be in the ASI. This particular GPS has been tested for accuracy of its speed readings, on the ground.

(5) I did say I was near max weight, probably about 98% of MTOW. By your own formula this would make an unrecognisable difference to the stalling speed.

(6) I covered the point about the vertical speed component in my previous post. For a rate of descent of say 500 fpm or even 1000 fpm this cannot account for such a large difference, as a simple calculation will show.

(7) No, there is no confusion of units here. The ASI reads mph as also does the GPS, and the book figures are given in mph also.

And your further comments:
Wind condition: This test was deliberately done on a day with almost calm conditions. There was a small difference (2 mph or less) in the up/downwind stalling ground speed.
Power: Power was slowly brought back to idle as the airspeed decayed.
CofG: I mentioned that this was near the mid position.
Use of non-aeronautical units: ???

[Genghis the Engineer]

My experience of GPS is that it takes considerable time to give a stable airspeed reading once you have a constant speed and height. By this I mean 20-30 seconds very often and I've never seen it give meaningful data during a deceleration to stall.

If doing an ASI calibration using GPS, I'd normally fly into wind and downwind (into wind being defined at altitude as that heading which gives the lowest GPS groundspeed) at a range of IAS values. I'd then take mean of each pair of groundspeeds to give TAS, adjust for density altitude to give CAS, then plot an IAS .v. CAS graph. I'd then take limited extrapolation of the curve down to my IAS stalling speed.

I agree that when checked you are only looking at a couple of percent error between GPS and TAS due to a 500 fpm descent rate.


Ultimately, my money is on an unstable GPS groundspeed reading due to a changing velocity vector. I suggest checking that by trimming the aircraft to a few knots above the stall into wind, confirming 5+ satellites and waiting for GS to stabilise over 30 seconds+. Then do the same downwind and see what you get.

But I'm often wrong !

G

[M14P]

Bluebeard777

Can I ask if your book values are IAS (I assume they are) and if so do you have a chart for position error correction?

It would be interesting to find out the CAS just to check if it is significantly higher than the IAS. This might be a good starting point.

[Bluebeard777]

I doubt that it would have taken up to 30 secs to get a stabilised GPS speed. Experiments with this unit on the ground, where a weaker signal is more likely, suggest a stabilised speed can be achieved in a few seconds. Also the test procedure was for the pilot approaching Vs to continuously call out the IAS to the observer, who compared this to the GPS and took notes. If the GPS speed was dropping when the IAS was stable just above Vs, the test conditions would not have stabilised and the readings would obviously not be a valid comparison (i.e. obvious to the observer). Having said that, I cannot prove now that there was no GPS lag and the test is worth repeating.

If the stalling speed (TAS or CAS) were really 55 mph, then the approach speed should be over 70 mph, which does not seem credible for this aircraft.

No graph of IAS v. CAS is available, creation of this would be a useful exercise. I need a day of stable air, with low wind speed, not so easy to get these days!

[M14P]

What sort of aircraft are we talking about here?

The TAS difference at 2900' density is less than 5 knots - i.e. you would expect to see nil wind gps speeds (or directional averages) about 5kt higher than observed.

As for gps giving too high a speed would not the horizontal component of velocity be less given any descent (or climb) since you can safely assume WGS84 to be 'flat' over such a small distance?

------------------------------------------------------------------

Anyway - has anybody had any really good, positive training experiences pertaining to stalling and slow flight? That should bring us a little closer to the original thread, too...

[hoey5o]

There is an awful lot of test pilots in here for a private flying forum.

I am surprised no one has mentioned incipient spin stage yet which, as I was taught , is another description of the wing drop. If I can recall it was defined as the first 180 degrees of uncommanded roll and the recovery required simply centralising controls and then standard UP recovery. When comparing this with the other technique of a bit of opposite rudder to prevent further roll, there was no difference in height loss, it was a lot simpler to do and no chance of flicking it the other way with the rudder as mentioned before.

[M14P]

Incipient can be used to describe anything leading up to a stable or oscillatory spin. In other words, there is auto-rotation but not all of the classic defining features of a spin.

As I mentioned before - one only needs to 'prevent further yaw' for as long as one is 'unstalling' the wing. The yaw/roll is present only whilst one wing is beyond the L/D peak that defines the stall (i.e. one wing is fully stalled and thus creating large amounts of drag). No stall = no wing drop.

It might also be worth mentioning secondary stalling (I've managed it in a P210 as well as YAKs etc!) which can be very 'energy state' related. This is why 540s slightly befuddled stall recovery description some pages back can be rather dangerous. Simply put (and without hogging the whole thread) some aircraft need rather more than just a quick shove on the stick and throttle before resuming normal service.

Well - anybody got any positive ideas about banishing stall/slow flight terrors? L-Plate, how's it going now?

[hoey5o]

M14P, with a name like that I guess you do a bit of Yak52 flying. Is there any chance you could make a comment or two on 52 flat spinning. Its a current thread in the tech log section. cheers.

[M14P]

I'm reluctant to start talking about individual cases here (especially the 52) mainly because I don't consider myself fully proficient with the 52 flat spin.

Genna at Skytrace or Ian Austin will help you out. Personally, I feel that the risk is there BUT it is smaller than you might have been led to understand. It's far more likely with very aft CofG.

Get ACTUAL training with Genna or Ian if you feel that you are regulary exposing yourself to the dangers. I feel that the 52 is pretty naff at stall turning well...

[strafer]

I think Cessna L Plate's been bamboozled away from his own thread...

[cessna l plate]

Strafer could be right, my head is approaching an incipient spin as we speak.

But... Thanks a lot for the input guys.

First, it's nice to know that I am not the only one that hates stalling. Every instuctor I ask says the same, and then ends the statement with "because it's boring".
Hmmm, how can purposefully making a serviceable aircraft in effect stop flying be boring??? Methinks someone has a strange sense of humour!

Secondly. I was wondering about a basic aero trip, if only to attempt a de-sensitisation of stalling. From the advise given, it would appear that this is indeed a sensible idea.

Thirdly, I can recover from the stall in any configuration, my instructor is a cautious fellow ( a good thing for a pilot), and would not have let me within 100 miles of the curcuit if I couldn't do it safely. My problem is quite simply one of a stomach emptying dread of the topic. I even asked him to demo a spin the last time we went stalling, but bottled out before he did it.

But there is a lot of food for thought there, so once again a big thanks

Cessna L Plate

[Gertrude the Wombat]

I even asked him to demo a spin the last time we went stalling, but bottled out I asked for a demo spin once. By far the worst bit was the incipient spin that I'd already been taught to recover from - the actual spin itself was lots less sick-making.

[shortstripper]

It's a bit like sea sickness ... if you are unlucky enough to be the type to be struck down, only more exposure is the cure. Unfortunately, unlike boats where you can spend hours or days getting used to it (or feeling ill from it :ugh: ), with flying there is no easy answer! Certainly, expelling any fear of it will help dispell the butterflies of anxiety, but I'm afraid you'd need to be a very rich man to actually do enough to de sensitise yourself.

IM