Single prop stall recoveries

[Genghis the Engineer]

I wonder if anybody can help me? I'm kicking off some research into stall recovery actions as used in single-prop (mostly training) aeroplanes. Basically we're looking at what is being taught in the various training regimes, comparing it to what's in the various aircraft certification standards, and then evaluating the sets of "generic" stall recovery actions on a range of civil piston-prop aeroplanes. Eventually we hope to identify whether there are any sets of stall recovery actions being published that might have problems (such as in FAA-land where many instructors seem to be teaching power-first recoveries, potentially a bad thing with a low thrustline?), or mismatches between instructional practice and test flying practice.


For civil aeroplanes, I've got plenty of good data sources, but I'm too far away from the military training system these days to know what's in use for any current types.

So, can anybody tell me the exact sequence / wording of actions for stall recovery as being taught for any single-prop military types, such as the G115, Tucano, Texan...? Also, what are the currently taught stall scenarios? -obviously level/CR, but also from land configuration turns? steep turns?

Better still, if you can give a document reference, I'll be astoundingly grateful, and might even say thank you! :ok:

G

[MrBernoulli]

Obviously the RAF Bulldog is no longer in service but I seem to recall, from my UAS and CFS staff days, that for a straight and level stall it was:

1. Simultaneously - Full power and control column centrally forward until the buffet stops.
2. Roll wings level.
3. Ease out of any ensuing descent.

Does that sound familiar to the ex-Bulldog folk out there?

[vikingdriver]

Mr Bernoulli has it right according to the latest 115 and Tucano teaching out there.
Generally the taught scenarios are:

Clean - Full stall
Configured - Full stall
Final Turn - First sign of stall warning (although instructor may mask artificial warners)
Final approach - First sign of stall warning although caveats as above.

[BEagle]

Agree with MrB on this. Remember that the RAF teaches pilots to recognise and recover from various types of stall with minimum loss of height.

A couple of refinements:

Full power also implies maintaining balance by keeping the ball in the middle and at the same time preventing uncommanded pitch attitude change.
Control column is moved centrally forward until the identification stops, then that pitch attitude is maintained.

Stall identification (forget 'signs' and 'symptoms' - you try teaching medical students using the RAF's daft definitions!) is the first of:

Buffet
Uncommanded wing drop
Uncommanded nose-down pitch
High rate of descent.

The 'ident' is often more obvious in proper RAF training aircraft as buffet, because stall warning turbulators are fitted to the inboard wing section, to generate buffet over the tailplane which the pilot can sense throught the control column. Far less obvious in civilian spamcans.

This 'ident' follows stall 'warning':

Speed low and decreasing
Control effectiveness reducing
Pitch attitude unusually steep for level flight
Airframe buffet
And it's all getting rather quiet

'Warning' = "Keep doing what you're doing and I'm going to stall!"
'Ident' = "Told you so!"

Whereas what I've seen from some civilian pilots is more likely to be:

Throttle closed from cruise speed, no attempt made to maintain level flight or re-trim, insufficient back pressure maintained to cope with self-inflicted out-of-trim condition, descent starts to build up as a result, speed slow to reduce.....eventually, at the first peep of the nanny-state stall warning horn or flicker of stall warning light, an almighty shove on the control column followed by a small throttle movement 'to save the engine'.....:hmm:
And someone seems to have spread stories about Corsairs 'torque rolling' and crashing onto carrier decks, so they're petrified of making brisk throttle movements (not slams!) at low IAS!

[Airbrake]

Beagle, your normally balanced postings have been let down by your last paragraph and it's dig at civilian pilot stall training.
I would suggest that the errors mentioned in your last paragraph are common to many students who are unfamiliar with stalling exercises during the early days of their training.

The use of trim during stalling exercises also has to be carefully briefed, and its use may not be appropriate on all occasions. As for a students reluctance to be more positive with the use of throttle during the stall training this is totally understandable because up to this point in their course they will have been told to be "smooth and progressive" with all their control inputs including use of the throttle. This will be one of the first occasions when the use of the throttle has to be far more positive than they are used to.

[BEagle]

No, the teaching of stalling and stall recovery by most civil flying schools is indeed entirely fine. A good 'demo' of the correct rate of throttle application should have rectified the student's hesistance to open the throttle briskly.

I said 'some' pilots. It is quite clear that some schools, or, more probably, some FIs do not bother to spend as much time on teaching stalling as others - and certainly the RAF - do. Not just my opinion, ask some of the FIEs. Some students have actually told me that they were taught NOT to use power at all during stall recovery, until they reach the 'recover from ensuing descent' stage......:hmm: Hardly 'minimum loss of height', I would suggest. I suspect that they weren't actually taught that - but that they simply weren't taught correctly.

How often have you come across students rushed into Ex12/13 with minimal previous flying time spent out of the circuit......:mad:

Incidentally, for a clean stall, I would suggest trimming to no lower than the normal gliding speed. What do you do?

[Dan Winterland]

Of the training aircraft I flew in the RAF, the stall recovery was the same. Which is why is was called "The Standard Stall Recovery". And it should have been drilled into every RAF pilot during his training and be automatic for use where approproate throughout his/her career. I shall write these from memory so that I can be picked up by someone - to test how well it worked with me!

When recognising the a stall at either the full or incipient stage, the actions are to:

"Move the control column centrally forward until the buffet stops while simultaneously applying full power and preventing further yaw with rudder. When the buffet stops, level the wings and ease out of any subsequent dive."

BEagle was alluding to the poor recovery techniques being taught by some flying schools. He and I used to instruct at the same flying club which had a large number of RAF QFIs - largely because it was an RAF club. We found the students we aquired rom other clubs frequently had picked up some bad habits. Gems such as 'picking up the wing with rudder'. The CFI at the club was pretty hot on such things and the standards there were high.



But whatever you do, don't mention "The Standard Spin Recovery"!!!

[Airbrake]

The problem with any PPL holder is that they will generally be far less current than any other professional pilot and bad habits or poor instruction will invariably take more time to be ironed out than would otherwise be the case.

As for trimming during stall exercises, I agree only trim down to normal glide or approach speed.

[Snow Dog]

1. Stick forward to recover from the stall.
2. Power to minimise height lose.
(Simultaneously, but in that order!)
It shouldn't need stating, but power also prevents you stalling again if you try and regain S&L (!!) having stopped the stall.
The difference comes in the nature of the stall warning. Eg, in the approach configuration, the artificial warning tells you you're approaching the stall but not there yet. Therefore, it is acceptable (and taught) to hold the attitude and power out of the warning. Hold the attitude is the student difficult bit; you don't lower the nose as it is assumed that in the approach config, you are close to the ground; and don't let the aircraft pitch up under the effect of power and induce an actual stall.
Interpretations of whereabouts in the stall one is, are usually the root of stall recovery actions.

[BEagle]

Snow Dog - who teaches that and where?

[CirrusF]

Obviously the RAF Bulldog is no longer in service but I seem to recall, from my UAS and CFS staff days, that for a straight and level stall it was:

1. Simultaneously - Full power and control column centrally forward until the buffet stops.
2. Roll wings level.
3. Ease out of any ensuing descent.

You forgot "add right rudder to counter prop induced yaw"


Throttle closed from cruise speed, no attempt made to maintain level flight or re-trim, insufficient back pressure maintained to cope with self-inflicted out-of-trim condition, descent starts to build up as a result, speed slow to reduce.....eventually, at the first peep of the nanny-state stall warning horn or flicker of stall warning light, an almighty shove on the control column followed by a small throttle movement 'to save the engine'.....http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/yeees.gif


This is not consistent with what I was taught on UK PPL nor French CPL - I think you are trying to provoke an argument.

On CPL, any height loss before the stall was a fail. We did stalls in all configurations, including recovery from a full stall wing-dropped situation, recovery from onset of aerodynamic stall, recovery with minimum height loss.

When I now teach stalling, I also teach stalling from a constant rate of deceleration as well as stalling from a constant height. Beagle's comment "no attempt made to maintain level flight or re-trim" is somewhat odd because that is approximately how you do a stall at constant deceleration, and it is a valid and useful stall to understand as it is more insidious than a stall from level flight, and is closer to the sort of stalls that really catch people out. It is also the stall procedure used in certification stalls.

[madlandrover]

Whereas what I've seen from some civilian pilots is more likely to be:

Throttle closed from cruise speed, no attempt made to maintain level flight or re-trim, insufficient back pressure maintained to cope with self-inflicted out-of-trim condition, descent starts to build up as a result, speed slow to reduce.....eventually, at the first peep of the nanny-state stall warning horn or flicker of stall warning light, an almighty shove on the control column followed by a small throttle movement 'to save the engine'.....
And someone seems to have spread stories about Corsairs 'torque rolling' and crashing onto carrier decks, so they're petrified of making brisk throttle movements (not slams!) at low IAS!

Sadly correct. As a current FI I've taken over students for skills test revision who've been taught a whole range of "interesting" techniques, usually leading to them being either extremely nervous of stalling, or perhaps worse still not understand the real dangers of an inadvertent stall. It's also a real shame when instructors themselves become nervous of stalling, because that gets passed onto their students incredibly quickly.

The problem with any PPL holder is that they will generally be far less current than any other professional pilot and bad habits or poor instruction will invariably take more time to be ironed out than would otherwise be the case.

Sadly also true. Given the cost of flying nowadays relatively few licence holders go out purely to practice general handling. It's something that we have to revise quite carefully during refresher flights - especially when creating a scenario to explain why it's such an important exercise. In all fairness the great majority of people are more than happy to revise those basic skills with an instructor, since they've got the sense to realise that it does make them safer!

To the original question: DEFTS technique is the one taught in every school I've flown with as a hirer, student, FI, etc. Minimum height loss, and don't hit the simulated ground...

[Final 3 Greens]

Ghengis

My experience of 3-4 FAA instructors in the US (some years ago) was not power first stall recovery, but rather releasing the back pressure or a gentle pitch down, then adding power.

The philosophy seemed to be to teach a recovery that could be used at low level as well as high, the theory being too much pitch down close to the deck, e.g. after takeoff, could cause CFIT.

They were very keen to detect the early signs of the stall, e.g. buffet and recover before the G-break; I believe this was not fear of the stall, but representing an FAA desire to recover early and prevent an incipient spin.

At times, the exercises felt more like stall prevention.

NB, I am not supporting or promoting this approach, just sharing my experience, in case it may be of interest to you. My license is PPL.

[PAPI-74]

2 main points I used to teach -

1) unload the wing first enough to silence the stall warner (this can be at 0KIAS whilst pushing forward from a vertical climb or hanging during a poor wingover).


2) apply the throttle over 2-3 sec to avoid rich cut

NOTE - if the throttle is applied whilst stalled, the yaw from the TQ and propwash on a more powerful aircraft WILL put you into a spin. Someting like the Firefly M260 will show signs of recovery then snap over. A Piper Lance (300HP Turbo) will also certainly bite back.

NEVER lift the wing with aileron or even rudder unless above 60 -65 KIAS.

[Farfrompuken]

Papi

I've done plenty of stalls as a low hours stude on Firefly M260s many years back.

Each time I employed the standard stall recovery:

simultaneously unload and apply full power. Level wings. Ease out of ensuing dive.

I don't recall the prop torque ever sending me into a spin!! And I was less aware of yaw than I am now.

In my hours as an instructor on the tucano with 5 times the HP many studes forgot to counter yaw; nowt happened as the power and unloading took us out of the stalled regime.

[Duncan D'Sorderlee]

"Some students have actually told me that they were taught NOT to use power at all during stall recovery, until they reach the 'recover from ensuing descent' stage...... "

Beagle, that is indeed correct - at least initially. In 'Stalling 1' students are taught that the ac stalls because of AoA; consequently, reducing the AoA is what recovers the ac. Application of power assists in minmum height loss.

Nevertheless, the standard stall recovery is as discussed above.

Duncs:ok:

[PAPI-74]

I used to demo a poor recovery in the Firefly, lifting the dropped wing in the stall. The Wing would rise about a foot then fall away violently. This killed several people without the altitude to fully recover - which was why I used to demo it. I just edged on the side of caution when teaching the as some students will always do something silly under pressure and distracted; especially while still slow. And we are only talking about a 0.5 - 1 sec lead with the cc fwd then power, still recovering with zero altitude lost from the incipient. The Lance has quite a bit of TQ - especially on take off - and although I haven't tried it, I was warned of it's vise by an instructor who had one as a toy - now a 15yr EasyJet Capt. And many students go straight into these straight from smaller trainers with their wife and kids.

I haven't flown the Tucano, but I have the PC-9 (which is vastly superior), which was a great platform for learning. I now operate a TP commercially.

As I am sure you are aware, piston Internal Combustion engines have intermittent combustion and the piston motion a produces a vibration. It generates horizontal and vertical shaking vibrations, fore and aft rocking moments, and torsional excitations galore. The torsional resultant is TQ.

Consider how a 4-stroke piston engine operates. During each 720° of crankshaft rotation, each cylinder in a contemporary 4-cycle piston engine produces a torque output during roughly 140° of crankshaft rotation, and requires torque input during the remaining 580° of rotation. The peak value of torque output is approximately 15 times greater than the mean torque output of the engine (the torque which the dynamometer measures). A 6 cylinder aero engine is producing this peak torque every 120 deg.
The aero engine also has a much higher RPM than a TP beng direct drive not via a reduction gearbox.
With the TP the only TQ is in the reduction gearbox giving a smoother power although still plenty there; increasing power levels are achieved through the increase of compressor air flow and increased number of power turbine stages. Most recent models enjoy the advantage of additional advanced technologies in materials, turbine cooling and aerodynamic design.
An IC engine isn't that easy, requiring an increase in cylinder size, dimension, piston travel and rotational force to drive it. For a low hours PPL to jump in and think they can handle the machine needs a lesson in respect - or good roots and stall technique.
If a student gets the habbit of unloading the wing 0.5 - 1 sec prior to unleashing 350 ponies and a turbo....is that a bad thing?

[Tourist]

Papi
May I just say re your attempt to suggest that ic aero engines produce more torque than a TP
Bollocks

[Genghis the Engineer]

Surely it's the other way around since the TP's reduction gearbox increases the reaction torque? Most IC engines (with the honourable exception of the Rotax products - which are sufficiently underpowered that it's pretty much a non-issue anyhow) don't have any kind of reduction so engine torque = reaction torque.

Going back to my original question, can anybody quote the actual words used in any military training manual or pilots notes?

G

[Dan Winterland]

"My experience of 3-4 FAA instructors in the US (some years ago) was not power first stall recovery, but rather releasing the back pressure or a gentle pitch down, then adding power.

The philosophy seemed to be to teach a recovery that could be used at low level as well as high, the theory being too much pitch down close to the deck, e.g. after takeoff, could cause CFIT."

The SSR advocates moving the control column forward until the buffet stalls. If the SSR is caried out at the first noticed sign of the stall, which in all probablility will be the stall warning there will be no buffet, so the control column will not have to be moved much - if at all. This is condicive to the aim of the exercise which is to recover from the stall, or apporaching stall with the minimum height loss.





"NOTE - if the throttle is applied whilst stalled, the yaw from the TQ and propwash on a more powerful aircraft WILL put you into a spin. Someting like the Firefly M260 will show signs of recovery then snap over. A Piper Lance (300HP Turbo) will also certainly bite back."

As for 'torque' putting you into a spin by applying power at low speed, I'm suprised to see this notion is still around. I too have recovered powerful aircraft from stalls with full power and have never entered a spin as a result. In my time as a Tucano instructor, I seemed to remember demonstrating the importance of controlling the attitude with the application of power at low speed, by the risk of an incipient spin didn't feature. The only RAF trainer in history where this was a problem was the Bolton Paul Baliol which had a tendancy to 'torque roll'. But this was as a reslut of the enourmous prop powered by a Merlin casing one wing to stall earlier through the angle of attack change with prop slipstream.




"Some students have actually told me that they were taught NOT to use power at all during stall recovery, until they reach the 'recover from ensuing descent' stage...... "

The stalling teaching exercise initially teaches recovery by angle of attack alone where the student has to notice the height loss. Then the recovery is developed to include power where the height loss is observed to be much less. But the recovery without power isn't the standard.



"I haven't flown the Tucano, but I have the PC-9 (which is vastly superior)"

If you haven't flown the Tucano, how do you know? I've flown both and they are very similar in capabilities. Although persoanlly I thought the Tuc had the edge as a pilot training platform. Certainly the view from the back seat is far better.

[Wholigan]

NEVER lift the wing with aileron or even rudder unless above 60 -65 KIAS.


I most certainly agree with the first half of this sentence, but how can you possibly mention ANY airspeed when discussing a generic stall recovery procedure, when people are discussing perhaps a couple of dozen different types of aircraft with differing stalling speeds and stall characteristics???

[PAPI-74]

I have just checked my notes from 1 EFTS. (Grob Tutor)

STANDARD STALL RECOVERY

Control Column Centrally Forward Until the Buffet Stops
(Hold the Resulting Attitude)

And

Simultaneously Apply Full Power (Balance With Rudder)
Level the Wings With Aileron
Ease Out of the Descent at Safe Flying Speed

Carry Out the After Take-off Checks

PS - 60 - 65 KIAS is a generic trainer type airspeed that is safe to roll level if the wing is still free of anymore load than + 1g . But as you say - seek individual type advise.

[Dan Winterland]

"Going back to my original question, can anybody quote the actual words used in any military training manual or pilots notes?"

Yes, sorry. Back to the original question. From the Firefly IGF. (Old Firefly, not the 260HP version.

19. Teach recovery from the stall using full power, this is the standard stall recovery. Note the height approaching the stall so that you can point out the height loss during recovery. The standard stall recovery is to:

a. Simultaneously, move the control column forward until the buffet stops and apply full power, using rudder to balance.

b. Level the wings with ailerons in necessary.

c. Regain a safe flying speed and ease out of the descent.

If you want the whole document, PM me with a snail mail address.

[chippy63]

Time for a trip down Memory Lane.
Dug out my Chipmunk T10 Pilot's Notes.
Went to Index- Stalling para 34.
(i) stuff on stall speeeds- 35 kts, power off, with flaps.
(ii) In all cases warning is given by slight elevator buffeting some 3 kts before the stall occurs. With power off at the stall, the nose drops gently accompanied by elevator buffetting and there is a slight tendency for the nose to pitch. If the stick is held hard back, the elevator buffeting is increased and a wing will drop. With power on, the pre-stall buffeting is increased and the wing drop at the stall is more pronounced.
(iii)Stalling speeds are reduced by about 2-3 kts with one pilot only in the aircraft.
(iv)With the canopy open, stalling speeds and characteristics remain unaltered.
(v)The stall in a steep turn is indicated by buffeting but there is normally no tendency to flick out of the turn.
(vi)Recovery in all cases is straightforward and easy ( my capitals!)

That's it in the book! Nothing more! As I recall, you let the nose drop, levelled the ailerons, neutralised the rudder, and the aircraft pretty much sorted itself out with or without a bit of power at the appropriate point.
Then straight on to para 35 on spinning, which does admittedly set out recovery procedures.
A lovely aircraft.

[Cows getting bigger]

Oh, what I would give to fly an aircraft that would always give me buffet before the stall :ok:. Most of the modern day stuff we GA pilots fly rarely gives a buffet, sometimes a wing drop (normally due to being out of balance), occasionally a pitch forward, thus leaving us with a rapid ROD as the only reliable indication of a stall. Even then, you can handle the controls like a complete idiot and the chances are you will still walk away. :bored: Of course, I'm still a big fan of the "unload simultaneously applying full power" technique as long as student pilots realise that it is only the unload bit that will un-stall the wing; the power bit is a bonus.

[chippy63]

Oh, what I would give to fly an aircraft that would always give me buffet before the stall

Well, yes, Fridays were best because it was a curry buffet....

I'll get me coat..

[John Farley]

"I haven't flown the Tucano, but I have the PC-9 (which is vastly superior)"

If you haven't flown the Tucano, how do you know?

Precisely Dan

[madlandrover]

It's diverging a little from the original post, but: I learned to fly in the Firefly 260 and do a fair amount of teaching on a Lance now. The Lance will bite you hard if you recover from a stall without using the pedals and use aileron instead, but it will also do a full power stall recovery with no attitude change if the controls are handled correctly - no danger at all of it getting truly exciting if a) the aircraft is correctly rigged and b) flown in balance! In 65 hours I had 1 inadvertent spin in the Firefly: messing up the second half of a stall turn, which was totally down to my mishandling of the controls at a low airspeed.

I'm not in any way trying to detract from PAPI-74's opinions - but in my experience on both types a standard stall recovery with power & control input simultaneously works nicely. Bear in mind that the power input is not designed to unload the wing (if anything it'll cause an involuntary pitch up), but rather to accelerate the aircraft into a climb faster to give minimum height loss.

[zkmkw]

I own an ex RAF Bulldog and this is a direct quote from the RAF Student Study Guide (Flying) Vol II FTP/3225M Vol II Chapter 10 Para 20
'Move the control column centrally forward until buffet stops and silmultaneously apply full power (balance) level the wings ease out of the descent at safe flying speed, trim and carry our full power check"

[Madbob]

I've read with interest all of the previous posts and there is obviously consensus about the "standard stall recovery" as taught by the RAF. That is as it should be.....

One difference between military and civil training is that military aircrew are exposed a lot more to "unusual attitudes" - I mean in the 3D sense! Whether taught on the Chipmunk, Bulldog, Grob or Tucano turning upside down is not a problem, there is a 5-point harness, you are wearing a parachute, the ac is stressed for the manoevre (if the recovery goes wrong) and the whole emphasis of training is developing "poling" skills to manoevre later ac at the extremes of their flight envelopes.

Contrast that with civil air training. The ac are mainly used in straight and level flight, emphasis is on safe navigation, and the procedural aspects of flying pax from A to B. The ac are not stressed for aerobatics (generally speaking), you are restrained by little more than a car seat belt, and the instructors have not just come off a fast jet tour! The student pilots are of all ages and not in the 19 - 24 age range, fit and keen as I was 30 years ago!

Hardly surprising there's a different approach! The question is which is the more realistic of what happens in the real world. I first flew solo in a Cadet Mk.3 after 21 launches and 92 minutes dual aged 16. Before doing so I was taught stall and incipient spin recoveries, cable breaks and I think gliding is a superb (and cheap) introduction to powered flying - it certainly has made me very conscious of having always having a "field" available for a FL.

MB

[CirrusF]

One difference between military and civil training is that military aircrew are exposed a lot more to "unusual attitudes" - I mean in the 3D sense! Whether taught on the Chipmunk, Bulldog, Grob or Tucano turning upside down is not a problem, there is a 5-point harness, you are wearing a parachute, the ac is stressed for the manoevre (if the recovery goes wrong) and the whole emphasis of training is developing "poling" skills to manoevre later ac at the extremes of their flight envelopes.

Contrast that with civil air training. The ac are mainly used in straight and level flight, emphasis is on safe navigation, and the procedural aspects of flying pax from A to B. The ac are not stressed for aerobatics (generally speaking), you are restrained by little more than a car seat belt, and the instructors have not just come off a fast jet tour! The student pilots are of all ages and not in the 19 - 24 age range, fit and keen as I was 30 years ago!



Not so - recovery from both erect and inverted spins is part of the syllabus for civilian FI course in France.

[Tourist]

Cirrus
Read his post.
He is talking about students, not student instructors.
And please don't tell me that you think having seen a couple of spins in training is the same exposure to UAs as a military career (or 5 minutes limited panel IF with me:eek:)