Symptoms of the approaching stall...

[Kerling-Approsh KG]

Would anyone care to offer 'the perfect answer' to the following request during an FI exam, please?

'Describe the symptoms of the approaching stall.'

(If you have a textbook reference, that would help, too).

Thanks

[BillieBob]

I wouldn't be so arrogant as to claim it was the perfect answer but, assuming we are talking about the 'Stalling 1' scenario...

High nose attitude
Low & decreasing airspeed
Less effective controls
Stall warning (if fitted)
Buffet

Clearly, this will not necessarily apply to a stall in manoeuvre when the first indication may be the stall warning or buffet.

[Flyingmac]

After demonstrating the unmistakeable pre-stall buffet of an EV97 Eurostar, I was asked why it never did it in the flare. 'Angle of attack' I said. Must be more to it though. Any offers? Keep it simple. I am. (simple).

[Nearly There]

Pretty much as BillieBob says.

From RD Cambell Book Stalling 10B-23

The Symptons Of The Stall:

1. Lowering of airspeed, when the throttle is closed and the A/C held in approx level attitude.
2. A reduced response from all 3 controls as the airspeed becomes lower
3. If a stall warning device is fitted (aural or flashing light) this will start to operate some 5 to 10 kts before the stall is reached
4. Buffet may sometimes be felt over the elevators as the smooth airflow breaks away & becomes turbulent over the inboard wing sections. Note this may not occur in all A/C when in the clean config with power off, but is usually present to some degree when a stall occurs with flap down and power on
5 The final sympton occurs at the stall itself and is a condition where height is lost and/or the nose drops even though the control column is held well back or even fully back.

[Whopity]

Classic Cambell, Symptoms shrouded in a bed of Waffle!

[fireflybob]

I would make a distinction between the "signs" of an approaching stall and the "symptoms" of a full stall.

Signs of an approaching stall:-

Decreasing airspeed, reduced control effectiveness, high nose attitude, light buffet, stall warner.

Symptoms of the full stall:-

Heavy Buffet, Nose pitching down, aircraft descending, wing drop.

Hope this helps

[Nearly There]

Whopity, Im not the only one that thinks that then! Im fairly sure that book could be a quarter of the thickness it is.

[Cows getting bigger]

Nobody seems to have mentioned yaw (assymetric blade effect) or increased power required to maintain altitude

[BEagle]

fireflybob, the military nonsense of 'symptoms' and 'signs' should be $hit-canned. Try teaching a medical student such bolleaux and he will quite rightly ask why then, if 'light buffet' is a 'sign', 'increasing buffet' is considered to be a 'symptom'? 'Symptoms' are something a patient tells you, whereas 'signs' are something you notice about a patient. Speed, attitude and control effectiveness are thus 'signs' - as are wing drop, nose drop and high RoD. Only stall warner bleeps or blinks and buffet are truly 'symptoms'....:hmm:

I prefer 'warning' and 'identification' - far more logical.

Warning = "Keep doing what you're doing and I might stall"
Identification = "There - told you I would!"

Also stall warning and stall ident systems are fitted to certain aircraft, so by using 'warning' and 'ident' you introduce the student to standard industry terminology.

And for those who cannot remember the 'warnings': 'SCAB' is a useful mnemonic:
S Speed low and decreasing
C Controls becoming progressively less effective
A Attitude becoming increasingly nose-up to maintain level flight
B Bleeps or blinks from the stall warner (or buffet in proper aeroplanes)

[fireflybob]

Beagle, thanks I like that!

[Kerling-Approsh KG]

So none of you mention stick position or pitch input?

[fireflybob]

So none of you mention stick position or pitch input?

Kerling-Approsh KG, please explain further

[Kerling-Approsh KG]

I think enormous harm is done by not highlighting that the stall almost always occurs with the stick aft of what a layman would call 'neutral' and with aft pressure applied to the stick.

However, the instructing world disagrees...

(Purists and aerodynamicists will argue with the imprecise terms I've used; rest assured they are there not because I hold them to be accurate, but because they will ease the discussion. Others will want to introduce the idea that inverted stalls occur with the senses reversed; my answer is that by the time someone is doing inverted stalling he should know the topic well enough to appreciate that 'nose-up pitch input relative to the local horizontal' is in fact what counts, except when stalling with roughly 90 deg of bank, etc, which again should be instinctive to those who should be doing it. Yet others will talk about CG-change (cargo shift)-induced stall and trim runaways, but my point relates to the GA fraternity).

[BEagle]

I think enormous harm is done by not highlighting that the stall almost always occurs with the stick aft of what a layman would call 'neutral' and with aft pressure applied to the stick.

The control column position and residual pitch force during the approach to the stall will depend upon the trimming technique you adopt....:hmm:

For the clean stall in straight flight, my recommendation is not to trim the aircraft to a speed below the best gliding speed. However, certain aircraft POH requirements might override this recommendation.

[djpil]

SCAB is what we teach in the colonies but you can't rely on those while manoeuvring in aerobatics and probably not enough in what I call the classic base-to-final turn stall.

Stick position to stall depends on cg, flap and power. Elevator trim doesn't make very much difference to position of the stick for a given aircraft lift coefficient. So, when flying aerobatic aeroplanes you've generally fixed those variables and the stick position is a very good cue that you are near the stall.

[cambridge]

'Describe the symptoms of the approaching stall.'

A). Light Buffet or
B). Stall Warner.

fireflybob ... Hector would be shocked!!!!!!!!!!!!!!!!!!!!!!!!!! :=:=:=

[fireflybob]

Hector would be shocked!!!!!!!!!!!!!!!!!!!!!!!!!!

Actually I don't think I ever saw my father shocked!

cambridge, I have a direct line to him and he says it's ok!

Sorry, you've lost me there - please explain!

[24Carrot]

Kerling-Approsh KG said:
I think enormous harm is done by not highlighting that the stall almost always occurs with the stick aft of what a layman would call 'neutral' and with aft pressure applied to the stick.

However, the instructing world disagrees...Is this really controversial? Leaving aside the 'aft pressure' which can be disguised by trim forces as Beagle says, I thought the stick position was the key, (at least for any given flap and throttle setting). I seem to remember I was taught this.

"Stick And Rudder" goes through this topic in a section called "The Silver Chain" in Chapter 9.

As I understand it for any given flap and throttle setting:
The wing stalls at a certain angle of attack (AoA).
The wing's AoA depends entirely on the 'whole aircraft' AoA.
The stable 'whole aircraft' AoA depends entirely on the tailplane AoA.
The tailplane AoA depends entirely on elevator position.
Elevator position depends entirely on stick position.
So the aircraft can only stall at or beyond one stick position.

Flaps and throttle introduce pitching moments which require different tailplane AoA's, so there are different stick stalling positions reflecting this. And the stable AoA is controlled by elevator, so I am ignoring extreme manouevres.

But for the standard landing configuration I thought there really was a 'stall position' for the stick/yoke, though it has to be 'sensed' rather than seen because you are looking out when it matters.

I am genuinely interested in hearing any other 'take' on this.

[cambridge]

Fireflybob..............

"Decreasing airspeed, reduced control effectiveness, high nose attitude" ???????????????????????????????????????????????
The comment about your late father was lightly written ... Hector was one the finest men I ever met and the best instructor.
If you do a test today with the CAA, you will be asked to recover (in the appproach configuration) at the first sign of "an incipient stall" ... I have given the answer ... no more and no less.
Do it otherwise and you fail. :(:(:(

[fireflybob]

cambridge, a very valid point but is the original poster referring to a stall "in the approach configuration" or an "impending" stall?

Yes I am more than familiar with the point you are making (I was trained, like you, by one of the Masters!). One presumes that the examiner should make clear when/where he expects a recovery (if unsure the candidate should ask?).

Although not an ex military man (I am tempted to say, thank goodness, but we better not go there) I did instruct for the military for 4 years. They made a clear distinction between being asked to recover at the incipient stage (activation at the stall warner) or the first symptom (sorry Beagle, identification) of the full stall (which can be any of heavy buffet, nose pitch down, a/c descending, wing drop).

One of my father's favourite questions was (usually holding model a/c in hands appropriately) can I stall when I am descending vertically towards the ground? Of course, we all know what the answer to that it since it's all a question of angle of attack which makes the point about high nose attitude! I mentioned that because I assumed we were talking about stalling from level flight. Am not sure what the PPL syllabus shows these days but a good flying instructor will indeed demonstrate that the a/c can stall at any speed/attitude - best done whilst looping (in an aerobatic a/c).

As you say Hector was one of the Greats - I think he would be turning in his grave when he sees the way some sectors of aviation have gone these days!

[P.Pilcher]

Quick point about stick position which occurred to me when reading this thread. Many, many years ago, when an almost brand new PPL, I took our Rollason Condor on a local flight. 2000' in the cruise correct engine speed, correct airspeed and nicely trimmed out. It was a lovely day and I was enjoying the view. Scanned instruments. Noted I had lost 200' with a small rate of descent noted on the VSI. Thought no more of it, trimmed the nose up a tad, stopped descent and carried on viewing the countryside. The trimming had, of course caused the stick to move bac towards me a tad. Scanned instruments again - small rate of descent noted again and elevator trimmer once again adjusted bring the stick back a tad more.
Then I got curious. "Why?" I asked myself: "this is the second time I have done this." So I investigated further, noted that my airspeed had dropped a bit, checked the tachometer was also reading a lower speed of propellor rotation, so I automatically hit the carburettor heat control. Engine de-iced itself, R.P.M. regained its former setting and the slight climb which now commenced was corrected by trimming the nose down. A careful check was maintained for carburettor icing during the rest of the trip.
Just a little example of stick position being another indication of an approaching stall. Fortunately, I had been well taught and knew what to do at 45 hours!

P.P.

[djpil]

24carrot - I give all my instructor trainees a copy of extracts from the Silver Chain - I wish I'd discovered that book 40 years ago. (and cg is also a significant factor in stall stick position)
Kerling-Approsh KG - the Australian CASA Flight Instructor Manual (http://www.casa.gov.au/scripts/nc.dll?WCMS:STANDARD::pc=PC_90300)has those std symptons so stall stick position is only mentioned by some schools and some instructors.

I just saw today that the US Congress passed the law mandating upset recovery training - I guess Australia will think of doing the same soon (in Australia that means sometime in the next 20 years). We start our first course for students here on Monday.

[britannia66]

cambidge has answered the question accurately.
Had the question applied to a full stall (which it did'nt), the the answer you want is ....
a). Heavy Buffet.
b). Sink.
c). Nose Drop.
d) Possible wing drop. :=:=:=

[Lightning Mate]

Although not an ex military man (I am tempted to say, thank goodness, but we better not go there)

Just as well.....

[Tmbstory]

Kerling-Approsh KG:

A technique that was used in cloud seeding operations in Australia, many moons ago, to find out how close you were to the approaching stall was to initiate a 5 degree level turn and if buffet occured, it was time to descend to the lowest safe altitude for deicing purposes and when done, then climb back to the minus 5 degree centigrade level and continue seeding.

The buffet was an excellent indication that the wing was close to the stall.

Tmb

[Kerling-Approsh KG]

Tmbstory, in entering that 5 deg AoB turn in level flight, you naturally applied back pressure and moved the stick aft, just as I said...

[Tmbstory]

Kerling - Approsh KG:

Sure did and that was the same during my whole Career.

Rgds

Tmb