Wing drop during stall [Archive]

Pilot DAR

7th Oct 2011, 11:40

Airplanes must be flown, even through the stall. Therefore, you cannot "give up" maintaining roll and pitch control while you are stalling, and expect the plane to be perfect without your input. For all the reasons mentioned, both wings will not stall in the same way, at the same time. The prop and torque might be factors, if you have significant power applied during the stall, otherwise really are not.

The design requirements for handling and controllability prescribe tolerable amounts of wing drop and heading change, with normal use of the controls throughout the stall. I therefore suggest to you that the aircraft really does not have worrisome wing drop, if, during the stall, the pilot can control the aircraft with normal use of the controls and keep it within the attitude allowances. Do not lock the ailerons central, and expect the wings to stay level or rudder alone - normal use of the controls approaching the stall.

I have flight tested aircraft which, due to flaws with the aircraft itself, could not be controlled within the tolerances of attitude, no matter how much pilot effort went into the precision of the stall entry. One in particular, would spin half a turn every time. Those aircraft very certainly had wing drop, and were not compliant with stall handling requirements.

For certain aircraft, your first indication of a stall (though you already know you're close) will be a gentle and controllable wing drop. All Citabrias I have stalled come to mind.

You can spend a lot of time tweaking an aircraft to eliminate slight wing drop, and never get it. It's one of those things to learn to live with graciously as a pilot.

rasti121

7th Oct 2011, 11:54

Doesn't usually the same wing drops on one type of aircrafts? I always assumed this is cause by the air flow from propeller (maybe the torque too?), statistically speaking, manufacturing imperfections, wind directions, aircraft mass and CoG etc should be random and lead to 50:50 (or close to) wing drop distribution.

flybymike

7th Oct 2011, 12:12

OK I am in troll mode. Lets get cracking here.
You should always pick up a dropped wing with rudder.:E

The500man

7th Oct 2011, 12:27

Yes you should also go "Weeeeeeeeeeeeeeeeeeeeeeeeeeeee!" at the point of stall because that's the professional thing to do, and it gives your passengers much needed reassurance. :E

Genghis the Engineer

7th Oct 2011, 12:36

Yes, I've heard that too - I usually ignore such idiots beyond the point of making sure they don't have permission to fly any aeroplane that I own a share in.

Unstall the wings, then control everything else.

G

bingofuel

7th Oct 2011, 12:51

You should always pick up a dropped wing with rudder.Or use rudder to prevent further yaw, as I am sure you know, using the rudder to yaw the aircraft in an 'attempt to pick up the wing' is just accelerating the down going wing, which may delay the onset of the stall slightly and result in a more equal stalling of both wings at the same time. Or if large rudder inputs are used may cause a spin entry in the other direction.

Pilot DAR

7th Oct 2011, 13:48

Or if large rudder inputs are used may cause a spin entry in the other direction.

Exactly. Been there, done that. The design requirements specify "normal use of the controls". It is not normal to control roll with the rudder, that's what the ailerons are there for.

In a few rare cases, I have seen flight manuals which state that the rudder is to be the primary control used during the recovery from a stall or spin - to the exclusion of the ailerons. This is because aircraft equipped the aircraft is equipped with spoilers, which go up with the aileron, and create undesired drag on that wing with large aileron.

So, if you're flying a certified aircraft, for which the flight manual does not recommend against the use of ailerons in stalls, you can, and should use them normally, to control the aircraft normally.

Pull what

7th Oct 2011, 15:22

I have seen flight manuals which state that the rudder is to be the primary control used during the recovery from a stall or spin - to the exclusion of the ailerons.

I always thought the elevator was the primary control that was used to recover from a stall or spin-looks like quite a few flight manuals need rewriting!

The500man

7th Oct 2011, 15:39

I don't think anyone would dispute elevator being the primary control used to unstall an aircraft, but when it comes to spinning, you as a pilot should read your POH as the recovery tends to be somewhat type specific. For example pro-spin aileron in a fighter jet can be sufficient to stop the rotation in a spin due to the adverse yaw generated.

Pilot DAR

7th Oct 2011, 15:57

elevator was the primary control

Well, yeah! I thought that we were past such basics by this point.....

That was the whole context, when I also wrote: "- to the exclusion of the ailerons." in the same sentence.

You don't work for EASA, do you PW?

bookworm

7th Oct 2011, 16:01

Also some lift is still produced above the stall AoA, so any difference in AoA between the wings will generate some degree of uncommanded roll. Then the down going wing will have an increased AoA (less lift, more drag) due to the relative airflow and the up going wing will have a decreased AoA (more lift, less drag) which will perpetuate the initial asymmetry and set you up for a nice auto-rotation.

Exactly. The difference between the unstalled and stalled regimes is that in the unstalled regime the aircraft is stable in roll rate (induce a roll with aileron, and the roll rate damps out). In the stalled regime, it's unstable, for the reasons 500man describes.

Blaming asymmetries between the wings is a little like saying "the ball bearing fell off the point of this pencil because this side of the point is slightly sharper than the other". Strictly speaking, it's true.

DB6

7th Oct 2011, 16:20

"Weeeeeeeeeeeeeeeeeeeeeeeeeeeee!" is almost obligatory :ok:.

FANS

7th Oct 2011, 16:33

Because each wing through its 30 year history is now very different!

mikehallam

7th Oct 2011, 16:55

An inauspicious, lop sided gust when crossing the hedge can spoil things too.

For light a/c a 'poorer' wing profile design could permit rapid transition from flying to stalled. The above case, may be a type leaning towards this area.
Not much fun if during the landing phase, which is a form of controlled stall.

mikehallam.

Pilot DAR

7th Oct 2011, 23:23

Yes, I agree, every fixed wing aircraft I have flown, recovers from a stall best, when the elevator (or stabilator) is moved first (nose down (when erect)) to initiate recovery.

I will try to not make unambiguous statements in the future. I'll also try to make unambiguous statements too! And I'll work on not making ambiguous statements either....

chubbychopper

7th Oct 2011, 23:41

Pull What....with the greatest of respect - push not!

but from the range I have flown over 20,000 hours plus Ive never come across one where the elevator was not the first flying control to be moved for stall or spin recovery (my bold)

If the power (which I agree is not a "flying control") has been reduced to a minimum, and one has ensured that no aileron is applied, I might agree with that statement. However, I think it is worth qualifying so that those with less experience than you have are not in any doubt about what constitutes "standard" spin recovery, and exactly why the actions called for should be accomplished in the correct sequence, which is (for an erect spin):

a) reduce power
b) eliminate any aileron input
c) eliminate any FORWARD elevator**
d) apply full opposite rudder
e) apply continuous forward elevator until rotation stops
f) centralise rudder input
g) ease out of resultant dive with elevator

** not generally published in traditional training manuals because it is unlikely that forward elevator deflection will exist in the lead up to an inadvertent spin, but this is an ESSENTIAL recovery action for spins that have become gyroscopically "accelerated."

To clarify therefore, a FORWARD movement of the elevator is certainly NOT the first action to recover from a spin. In the case of an accelerated spin this is probably the WORST thing one could do, and for a number of reasons that I will be pleased to expand on to those who may have an interest.

n5296s

8th Oct 2011, 07:00

For certain aircraft, your first indication of a stall (though you already know you're close) will be a gentle and controllable wing drop. All Citabrias I have stalled come to mind.

@PilotDar... ooh, if ever you're in the Bay Area, I can show you a real treat... a Citabria that is utterly unflyable in a sustained stall ("falling leaf"). It rolls hard and quickly into a left knife edge, no matter what you do. I was flying with my acro instructor and he of course derided my ability to fly properly... until he tried it. (Proviso: they may have retrimmed it and fixed it since, this was a long while ago).

Pilot DAR

11th Oct 2011, 12:24

Funny how you can own a plane for 24 years, fly thousands of hours on it, and realize, that there are still things you don't know about it!

While leafing through the flight manual for my C 150M, during a long flight yesterday, I happened across the procedure for spin recovery. It is:

(1) RETARD THROTTLE TO IDLE POSITION
(2) APPLY FULL RUDDER OPPOSITE TO THE DIRECTION OF ROTATION
(3) AFTER ONE-FOURTH TURN, MOVE THE CONTROL WHEEL FORWARD OF NEUTRAL IN A BRISK MOTION
............

Ive never come across one where the elevator was not the first flying control to be moved for stall or spin recovery-still you live and learn dont you!

I guess we'll both live and learn PW!

Pull what

11th Oct 2011, 14:14

**** OK -Yes Pilot Dar and Chubby you are quite correct I made a mistake there. Ive got a great excuse too but I won't mention it as I do not want to set a precedent or spoil the moment!

In fact PD my incorrect technique of moving the CC forward first will work on your C150 (normal Cof G and config) but you probably knew that.

I am interested in your standard recovery Chubby, Ive not come across that, as written, as a standard recovery before, where did you get that from? I am asking that out of interest by the way-not trying to be clever!

In fact looking at what you wrote again this is the bit that i do not remember seeing before
c) eliminate any FORWARD elevator**

So yes please do elaborate

The500man

11th Oct 2011, 19:33

I am interested in your standard recovery Chubby... where did you get that from?

Yeah I'd be interested to find out too.

b) eliminate any aileron input
c) eliminate any FORWARD elevator**I was taught these together as "centralise". Meaning stick and rudder neutral.

e) apply continuous forward elevator until rotation stops

Not sure what is meant by this. How much and how fast? I can see it being counter-productive on types where the elevator masks the rudder.

Pull what

12th Oct 2011, 01:51

e) apply continuous forward elevator until rotation stops That is deffo part of the standard recovery, in fact in some types( or at some c of g's) you will not recover unless you hold the CC/ stick forward onto the stops. Lack of full forward stick was cited as reason for some Chipmunk pilots being unable to recover i seem to remember

shumway76

12th Oct 2011, 04:24

With regards to elevator control during stall, maybe the best wording should be "Release any back pressure on the control column"?

That way, it can mean DO NOT PUSH CC FORWARD, but just relax it...?

mad_jock

12th Oct 2011, 10:35

Which is why there is no such thing as a standard spin recovery

Pilot DAR

12th Oct 2011, 11:23

Which is why there is no such thing as a standard spin recovery

Indeed! And even for the same aircraft type under different loading conditions. Though many of the lighter aircraft I have spun, had recoveries which were basically the same regardless of weight and C of G position. The C-185 and 206 are noticeably different depending upon the C of G position.

The C 206 can be very "bobby" and pitch sensitive when you push the nose down. It's easy to get into negative G, and it requires delicate control input to get it just where yo want it.

I found the Caravan's spin characteristics to be extremely different based upon C of G position. At gross weight forward C of G, it could not be held into a spin for as much as a turn, a dramatic spiral dive resulted (recovery can only be safely accomplished by referring to an accelerometer). At aft C of G was completely different, requiring full opposite rudder and controls forward (nose down) to be applied and held for 3/4 turn to get it out.

These very different characteristics demonstrate to me that although these aircraft can be safely spun and recovered, when properly planned and equipped, in ideal circumstances, casual spinning would be a very poor idea.

That said, each of these aircraft were naturally very resistant to entering a spin, so it would take real mis-handling to get you there in the first place.

The standards for handling which must be shown for approved maneuvers generally require a demonstration that "unusual pilot skill, attention and strength" are not required. If the recovery technique varies a lot by configuration, the skill and attention elements of that requirement may not be met. That said, of course, there are also very specific requirements for aircraft handling during stalls and spin (if desired for approval).

SEP Flyer

12th Oct 2011, 12:35

I started my PPL training 3 years ago, and we did not do any spin training. I got my licence last year, and I have still never had any spin training. The only advice I was given about getting out of a spin in a C152 was to 'let go of everything, it will sort itself out'.

I'm told that spin training was part of the PPL training many years ago, so should it still be taught as part of a PPL? If it's not taught now, how many newer pilots (like me) would know what to do to get out of a spin? And reading these posts, 'letting go of everything' does not seem the best option ....:eek:

mad_jock

12th Oct 2011, 13:53

Don't believe that in a C150 or for that matter a C152.

During my FIC the instructor was in a steep turn right on the nibble of the stall with full power on.

His words were I have never mana-----

While saying he put a couple of reversing roll inputs in.

The aircraft flicked over the top and we were in a fully developed spin going about 3-4 times faster than they normally do. It wouldn't recover with the POH spin recovery and after what seemed ages he applied power as well as rudder and it came out not very far off the ground.

Its an optional part of the syllabus, I used to do it with my students if they wanted to but I didn't push it if they didn't. Its much better to know the danger attitudes and get the student to recover when they see them than teach the spin recovery. Most spins occur in slow stages of flight when you are so near the ground it doesn't matter how much training you have had you won't have enough altitude to recover.

SEP Flyer

13th Oct 2011, 16:51

It is confusing when there seems to be so much contradictory advice about getting out of a spin in a C152 - this is just one of many articles about 'letting go' of the controls and it will self recover. I've never spun a C152, but those who have, which method do you use?

"Spinning the Cessna 152

It is a hallmark of the tricycle wheeled Cessna 150/152/172 aeroplanes that they are difficult to deliberately spin when they are loaded in compliance with the Utility Category Certification. Load a couple of passengers and some baggage into a Cessna 172 and it becomes easier to spin, but the aeroplane is not in the Utility Category! To learn what a spin is really like you need to fly one of the following aeroplanes: Piper Tomahawk, Slingsby T67, Chipmunk, Condor, or most 'classic' training aeroplanes.

We are flying the Cessna 152 however so let's look at how we can simulate the spin...

'Spin entry'

There are two ways to enter the spin in a Cessna 152, you either flick/snap the aeroplane in, or you enter with some power. Flicking it in is very violent, this is often the way that frightens the student pilot and involves reducing the speed to around 50KIAS and applying full up elevator and rudder violently. The aeroplane inverts and enters a spin.

The nicer entry is to apply 1500 RPM and at 40-45KIAS apply full rudder and up elevator, this way the aeroplane enters the auto-rotation smoothly. Once established you must close the throttle.

In the spin

The Cessna 152 will spin for one turn and then it enters a spiral dive, so one turn is all this author does with a student! It's enough to get the point across. The aeroplane rotates due to the differential lift of the wings because there is yaw, the faster wing is developing more lift and so rotates upwards, at the same time the nose is yawing in the same direction. The aeroplane descends like a sycamore seed.

The Cessna 152 will recover if it is correctly loaded, and the power is at idle, by simply releasing the controls."

The500man

13th Oct 2011, 17:12

The "let go of everything" method does not work on all aircraft. I seem to remember being told that this method is dependent on the A/B ratio (ratio of weight in the fuselage, to weight in the wings) of the aircraft as it effects the gyroscopics of the spin.

In terms of recovery training if you are taught to recognise the onset of a stall, and to fly the aircraft in balance you should never get into a spin (unintentionally).

Pilot DAR

13th Oct 2011, 19:00

in a Cessna 152, you either flick/snap the aeroplane in

Whoa there! :eek:

Whomever is being quoted should be much more cautious than to say this! If the 152 involved here is an Aerobat version, and an areobatic instructor is aboard this is acceptable. Otherwise, most certainly not! What is described here is a snap roll, and introduces all kinds of structural loads which a "normal" category aircraft is not designed to withstand. This is how a fool breaks a plane!

If in doubt, read the instructions! The Flight Manuals for spin approved Cessnas describe how to enter a spin why not do it that way?

Generally, the phrase "slow deceleration" is included in the description of spin entries. There are all kinds of other warnings about not having higher speeds and abrupt control inputs.

As for recovery, do what the flight manual says. If you are flying an aircraft which does not have a spin recovery described in the flight manual, you really should not be spinning it, unless a number of special precautions and authority has been granted.

The let go of everything method is not the quickest way out of any spin, but with altitude available, and a later prompt recognition and recovery from a spiral dive, it will be adequately safe on a small certified GA aircraft. The key being, when letting go of everything, you're not making it worse. That said, if you have inadvertently spun any plane, you were probably maneuvering close to the ground, and you're all done then. Aside from buggered up aerobatics or instrument flight, I cannot imagine how an accidental spin would occur at altitude.

The "let go of everything" method does not work on all aircraft

Very true. This is why nearly all aircraft are prohibited intentional spinning!

The Caravan recovered at Vne AND 2.8G, descending at 9200 FPM. Hopefully that warns most pilots away from casually attempting such things. I highly recommend competent spin training (including reading the flight manual!), in an approved aircraft type, and not spinning anything else!

Here's the video clip of my Caravan spin for those who have not seen it linked here before....

C208 spin clip.m4v - YouTube

mad_jock

14th Oct 2011, 07:05

And the other thing is that only a couple of spin modes will have been tested or maybe only one that is in the POH.

The spin mode I got into certainly wasn't the normal one so if you don't go into the spin as the book says you have no guarantees that it will come out using the book method.

Pace

14th Oct 2011, 09:00

Not yet but I do teach pilots to be FIs and not make unambiguous statements.
Obviously Ive not flown every aircraft but from the range I have flown over 20,000 hours plus Ive never come across one where the elevator was not the first flying control to be moved for stall or spin recovery-still you live and learn dont you!

Pull what

Go and do an Initial or recurrent in a Citation and I guarantee the examiner will jump down your throat if you pitch forward:E for stall recovery.
You power out wings level nose on horizon.

Pace

mad_jock

14th Oct 2011, 09:25

Not disagreeing that the attitude of wings level nose on the horizon will be sufficent to unstall.

The fact is that for your wings to stall they will be at 15-17deg AofA.

By bringing the attitude down to nose level with the horizon you will be reducing the AoA to 3-4degs. It may be that means you physically move the stick forward or only ease the pressure the difference is more of an indication of incorrect trimming ie if you have had a trim runaway and its right the way back you will have to push forward, if its just cack handed flying you will just have to stop pulling back as hard.

But fundamentally your going to have to do something with the elevator to get it unstalled.

As i have said in previous threads I actually quite like the idea that there is a limit to how much you can lower the nose for a checkride. It takes all the you didn't do enough /did to much personal opinion out of it.

Pace

14th Oct 2011, 10:07

Mad Jock

This came about before in a previous thread and I C-cked up the explanation then ;)

Obviously putting the aircraft into a stall will increase the AOA until the aircraft reaches the incipient stall.
In the Citation you hold that AOA and go for full thrust!
Any forward movement on the control column will result in a high height loss.
And no! few of the older Citations have stick shakers.
So basically you power out reducing AOA as the aircraft gains speed

I reverted to instinct on one recovery pitching forward while going for full thrust and apart from being told off the height loss was significant compared to the method taught.

I believe the Husky in a flight test was held back in the stall with the control column fully back! The tester went full power in that attitude with the aircraft clawing its way back into flight?

Pace

mad_jock

14th Oct 2011, 10:21

You have to do something to get the wing flying again or it doesn't matter how much power you put in you won't unstall it.

The Co of drag goes through the roof while stalled and if you maintain your AoA all the power you put in will just be getting dumped into the air.

You have to bring the AoA below the critical before you have any chance of powering out.

As you have said you bring the nose to the horizon which will be a change in attitude of at least 10degs.

Incipent stalls fair enough hold the atttude and power out but if you have actually stalled you need to do something to reduce the AoA.

This is all presuming your not flying a lightning or something else which can stand on its tail and :mad: off

Pace

14th Oct 2011, 10:31

This is all presuming your not flying a lightning or something else which can stand on its tail and off

Mad Jock

Obviously at some point the AOA will reduce and the amount of power available will have a bearing! You talk of the lightning but look at a rocket which defies gravity or even a Harrier or a Canon ball out of a canon.

We are looking for the best method for given aircraft which will result in minimum height loss at the recovery and in the Citation its not making a positive pitch forward.

Note for light aircraft the bit I added on the previous post on the Husky!
My instincts are to pitch forward but its not the best method for all aircraft although reducing AOA in small increments while relying more on power/thrust can be.

Pace

mad_jock

14th Oct 2011, 10:58

They are working on a different principle which is basically a force which is more than the weight they arn't really flying its more brute force and Newtons laws with force vectors.

I am not saying it will be a positive pitch forward it will just be a reduction. The citation might very well need a ball hair where as others need a hefty fist full but it still needs it.

The Statement you can power out of a stall is miss leading you don't actually if the wing is stall all you do is convert all the power into tubulance.

BUt if you say stall at 30degs nose up and I mean stall not when something starts bitching at you. If you maintain that 30deg attitude you can chuck as much power out the back as you like you won't unstall it.

If you have enough power to balance on your tail and start forgetting about aerodynamics and start using Newton to remain in the air you may well be able to accelerate away which will then change the AoA which will unstall the wing.

Now incipent stall your not stalled so you don't need to do anything positive because the wing is still flying. If you have enough power to dig yourself out of the dirty side of the curve crack on but that is a completely different situation to the wing being above the critical angle of attack. Most planes don't have enough power to dig themselves out of the dirty side so they pitch to get into a energy state that they can.

Comparing what's happen and the reasons for doing things between fully stalled with the wing over crit AoA and incipent with the wing unstalled is like comparing chalk and cheese.

The500man

14th Oct 2011, 11:14

You might not need to pitch forward due to the movement of CP when the aerofoil stalls. Obviously it will depend somewhat on the wing configuration.

Pace

14th Oct 2011, 11:22

Jock dont disagree with one thing you have said.
The point that needs to be made is that different aircraft require different techniques to recover from a stall with MINIMUM HEIGHT LOSS.
Use conventional recovery techniques on the Citation and the VSI will go in a direction you dont want to see it.
It is MINUMUM HEIGHT LOSS recovery for a particular aircraft which should be the goal and they really do differ.

As for the Husky

The mild stall behavior of the Husky was the result of a bit of aerodynamic legerdemain. The wing itself is characterized by an abrupt stall break with little warning -- but when you take a Husky to a high angle of attack, the tail incidence is set so that the tail, which is providing downforce to counteract the down-pitching moment of the wing, stalls first.

When the tail stalls -- with plenty of warning -- the wing pitches down before fully stalling. The result is an apparent mild stall with full aileron control retained throughout.

Pace

mad_jock

14th Oct 2011, 11:53

But is this a incipent stall you are recovering from or a fully developed?

If it is incipent then there will be different methods or putting it better shall ways say degrees of how much action you must take with the elevator.

For a fully developed you have to decrease the angle of attack even if its for a brief moment to allow the acceleration through the very beginning of the drag curve.

And even if the CP does move which then unstalls you if you don't change the position of the elevator you will be back to where you started, if you don't have enough grunt to dig yourself out of the dirty side of the curve.

Pilot DAR

14th Oct 2011, 12:45

But is this a incipent stall you are recovering from or a fully developed?

Indeed! As the original question relates to a stall, not the approach to a stall, it is fair to assume that the stall has occurred prior to the conditions described. A stall has occurred when the pitch control can no longer be maintained, or the elevator has been held against the up stop for three seconds. Until one of those two has occurred, the aircraft has not stalled - it could have approached the stall (incipient stall). With the exception of those few aircraft which are pitch control limited (Ercoupe being the only example I have flown), all other aircraft will pitch over on their own if allowed to stall at idle power. (high power is cheating) Once pitched over, continuing the control input that got you there is likely not going to get you out. You're going to have to lower the nose somewhat - though I agree, probably not full down!

I was flight testing a modified Robertson STOL C 206. I could not figure out what it's stall speed was (a flight test requirement). This was because I could not figure out when it was stalled. I could fly through a 5 knot speed range while maintaining some pitch control of the aircraft, though it was a bucking bronco. I sought expert help, in defining the stall. it was much more simple than I thought; what was the lowest speed at which I had full pitch control? Yes, I could achieve slower speeds, but the aircraft was not wholly under my control - it was stalled already. The stall had occurred at the higher speed.

Pace, I have never flown a jet, but I have to believe that they will fly and stall like a propeller aircraft (it's a design requirement). I agree that when you are warned that you are approaching the stall, powering out of it with no pitch change will work. Several aircraft types I fly will power out, and climb away in any configuration, as long as you are flying, and don't pull back more - but they are not stalled yet - just very close! I have done this with the controls held to the nose up stop, but it was not stalled. Were it to stall, it's going to pitch over, and I will not prevent this with elevator control. If I add power, it will change the effect of the elevator.

I think, for the purpose of a discussion of pure stall aerodynamics and handling, things would be more clear with a discussion of power off entry, actual stall, and then recovery. I do realize that this is not the norm in terms of minimizing altitude loss, but it is the most appropriate for understanding how the plane flies. Perhaps a glider pilot will support me on this?

Pace

14th Oct 2011, 12:54

Mad Jock

We talk of incipient or fully developed but one can become the other in the flicker of an eyelid.

I am sure that in all my recurrents two methods of recovery would be taught if incipient and full were so far apart.

Ok its incipient so use recovery A now its full so use recovery B :E
But its not its one recovery method with the Citation.

Incipient maybe the flavour of the month as most training is safety based and that word is high in our minds but incipient or full low level in poor vis and the real world can be so close that the difference in practical terms is negligable.

If you get my Gist?

There is a whole world of difference recovering from a stall at 15K and one at 500 feet agl.
Hence why I stress to look at recovery with minimum height loss and the methods used will vary aircraft to aircraft.

BTW I add I am fully aware of AOA, full stalls, incipient stalls, drag, power etc ;)

Pace

Pull what

14th Oct 2011, 19:51

Go and do an Initial or recurrent in a Citation and I guarantee the examiner will jump down your throat if you pitch forwardhttp://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/evil.gif for stall recovery.
You power out wings level nose on horizon.Thats strange I have been flying the Citation for 32 years never came across that before, mind I do renewals at Cessna and what would they know eh?

In fact if you read this Cessna flight test you will see standard recovery is to lower the nose by 5 degrees
http://blackrockglobalservices.com/files/cj4.pdf

frontlefthamster

14th Oct 2011, 20:19

Obviously no one here went through CFS...

You can't pitch the nose forward; how far forward it is is set by the designer.

You can pitch the nose down, assuming you stall in erect flight.

Crikey, exam wing would have you in stocks for 'pitching the nose forward'...

And they'd be absolutely right...

BEagle

14th Oct 2011, 20:38

Go and do an Initial or recurrent in a Citation and I guarantee the examiner will jump down your throat if you pitch forward for stall recovery.
You power out wings level nose on horizon.

Fortunately even the FAA has now woken up to such complete and utter drivel. The 'minimum loss of height' requirement has been totally misunderstood by idiot FAA examiners, so now the emphasis is firmly on reducing AoA.

Airbus and Boeing both agree that 'TOGA and don't descend' is highly likely to cause a stall from the stall warning phase. So now they've re-invented the wheel to stop the stupidity caused by dim-witted FAA idiots. The recovery is now (and it's the same for both a full stall and an incipient stall):

1. Disconnect AFS and ATS.
2. Pitch to reduce AoA - this may require use of trim if the AFS has trimmed to a low speed.
3. Level wings.
4. Thrust as necessary.
5. Speedbrakes IN (if extended).
6. Resume safe flight path.

If you don't believe me, go to EASA Safety Conference: Staying in Control - Loss-of-Control (LoC) Prevention & Recovery (http://easa.europa.eu/conferences/loc/) and click on 'Presentations' - then view the one on stalling.

frontlefthamster

14th Oct 2011, 20:58

BEagle,

Just for my benefit, could you explain why by being presented at a conference, a particular technique becomes of significance?

That conference was the worst equivalent of Dracula presenting on the topic: 'why the Blood Bank seems to be losing stock'... All the folk who set the scene for AF447 et al on their hind legs pontificating about how they were not responsible for their failings, if you ask me...

To address the fundamental point here, could we not all simply fly our aircraft and their wings? On the Citation series, for example, a recovery which relies upon thrust alone seems perfectly acceptable, within bounds, at least in the flight testing I did on the type... Pitch/power, etc? Anyone?

Pull what

14th Oct 2011, 21:04

Pitch to reduce AoA - this may require use of trim if the AFS has trimmed to a low speed.Getting away from Citations and Airbuses (and I am type rated on both) and back to a standard stall recovery for a PPL Ive always understood and taught that you pitch forward to unstall the aircraft which is the same as above, although I think its easier for a PPL student to understand the term 'unstall' than 'A of A' for practical purposes in the air.

Pull what

14th Oct 2011, 21:13

You have to do something to get the wing flying again or it doesn't matter how much power you put in you won't unstall it.

Some revision needed on propwash I think Jock

Genghis the Engineer

14th Oct 2011, 21:29

Some revision needed on propwash I think Jock

It also is somewhat type dependent.

All aircraft have a pitch change with power - mostly nose-up, occasionally nose-down.

Also some aeroplanes have a stall which is actually a pitch authority limit, rather than a true aerodynamic stall. This is particularly true at forward CG conditions.

An aircraft with either sufficient pitch-down with power, or insufficient elevator authority to achieve a true aerodynamic stall, can potentially be recovered with power alone.

Three aeroplanes I can think of for which this is true most of the time are the Thruster TST, Goldwing and the Flightdesign CT.

That said, Mad Jock is certainly correct for most common SEP types.

G

Pace

14th Oct 2011, 22:38

Pull what

That is a flight test on the CJ4 very nice but not exactly the Earlier Breed of Citation 500 series. Even the 500 series had different wings! Citation 550 (2) Era about 1982.

Oh well I will tell all 3 examiners that they are wrong!
5 degrees? what from the stall AOA or the incipent AOA?
Could you in a stall recovery be so precise as to pitch 5 degrees?
The word Pedantic springs to mind

BEagle

The 'minimum loss of height' requirement has been totally misunderstood by idiot FAA examiners

So the Idiot FAA examiners can learn from EASA/JAA then maybe their excellent part 135 accident stats which are almost Airline rates will match the attrocious AOC ops stats

Pace

mad_jock

14th Oct 2011, 22:41

Pace but the simple fact that you nose is on the horizon means that you have reduced your AoA.

You must be what 20degs nose up with power off when you start to recover. Then reducing that down to nose on the horizon is reducing the AoA by at least 10-15 degrees.

Its a very sensible procedure to specify. Stop people over cooking it and pointing at the deck and gives everyone a set attitude to obtain that will be guaranteed to work and not cause secondary issues.

The only reason for a incipent stall to turn into a full stall is by increasing the AoA.

And if you teach AoA all the time there is a huge logical follow through about why the stall speed changes for various conditions.

Pace

14th Oct 2011, 23:04

You must be what 20degs nose up with power off when you start to recover. Then reducing that down to nose on the horizon is reducing the AoA by at least 10-15 degrees

CJ4 Stipulates 5 degrees so 15 degrees nose up on your calcs?
I really think its easy at home on the computer to discuss theory different to try it practically.
The Idiot FAA examiner method gave a minimal height loss. My semi conventional recovery lost a lot.
At 400 feet he would have recovered I would have hit the ground.

Pace

mad_jock

14th Oct 2011, 23:26

Come on by far the most likely chance in stalling is when you have decended with power off and the AP has alt captured and the PF hasn't powered up and your going to have more than 400ft under you if that happens.

The only time you will be that close to the ground will be on approach. Which is why we have stabilised approach criteria to protect against it. If your AoA has got that high (or speed that low if you must) your under Vref and there has been multiple lapses in both flight monitoring and also flying.

I have come across the same procedure in the turbo prop world and the FAA pilots have been adamant that you power out saying if you drop more than 100ft you fail. They have all sorts of certs with unusual attitude training in sims that has taught them to use the rudder to lift the wing in a flight upset as well. You mention that the arse fell off an airbus doing that and you get blank looks or some ****e about airbuses are dangerous. It is quite funny though watching them straining away against the yaw damper for all the good it does them.

They are quite upset when they fail, and its not been me that's been doing the failing I might add.

Pace

14th Oct 2011, 23:43

For engines
installed below the wing, applying maximum thrust can
create a strong nose up pitching moment, if speed is low.
For aircraft with engines mounted above the wings, thrust
application creates a helpful pitch down tendency.

From the EASA discussion doc link posted by BEagle ! Citation has engines mounted above the wings.

Nose down pitch control-Apply
Nose down pitch trim-As needed
• Reduce the angle of attack
• Some altitude loss may be
necessary

Again from the new recommendations but note the referance to some altitude loss may be necessary? Firstly how much is some? and how much reduction in AOA.
Having read the new recommendations I will write to the Examiners in question for an update on their recommendations regarding the document.

MadJock

Take your points regarding stabilised approach but consider wind shear?

multiple lapses in both flight monitoring and also flying.
Isnt that the case in ANY inadvertant stall on a stabilised approach or infact any point of flight?

Pace

PA31flyer

15th Oct 2011, 05:04

Interesting thing is in a C172 the right wing is actually at a slightly higher AoA than the left due to the fuel return, the fuel return on goes to the right. Also increasing the weight of that wing. This causes the wing drop, normally seen to the right. Mind you the margins for these differences is very small. Cross wind in the air is also a cause as it changes the relative airflow over the wing as the plane is a relativity slow speed.

BEagle

15th Oct 2011, 07:18

Oh well I will tell all 3 examiners that they are wrong!

Good! Please do.

Firstly how much is some? and how much reduction in AOA

There is NO mandated maximum acceptable height loss. As regards quantifying the specific reduction in AoA, that is something I told them had been omitted from their procedure. Current teaching for light aircraft stall recovery pitch attitude states (or should state) 'contol column centrally forward until the warning/ident ceases, then maintain that attitude'. That would seem equally applicable to large aircraft stalls - it's what I used to use when taking the VC10K to the stall warning during full flight tests. If applied promptly and correctly, the attitude change can be very small indeed and the loss of height will also be very slight.

It's important also to note that you could be very close to the stall when the stick shaker operates (assuming the aircraft is so fitted) if the wing has collected leading edge icing - which might not be obvious at night or in cloud. Which is why the recommendation is to recover using the same technique whether you receive a stall warning or a stall ident.

Pace

15th Oct 2011, 08:44

BEagle

As far as I can make out these are discussion documents for interested parties including the FAA.
in the documents it acknowledges the differences of effect on AOA between adding thrust on jet aircraft with engines above and below the wing.
Adding full thrust with engines high above the wing causes a reduction in AOA.
The Citation is such an aircraft as are many heavier jets.

Mad Jock implies that stalls do not occur in stabilised approaches I presume from that he considers them to only be in the areas of takeoff and cruise??

I can assure you that a postive push forward as may be used in a light piston aircraft would result in a large loss of height in the Citation.
a steady reduction will result in minimal height loss with full application of thrust.

How you can be so demeaning of examiners who have spent all their lives in the industry just because they happen to be FAA Looses me! One spent 10 years with the FAA accident investigation.

Would I make a positive push down in a low level stall in the Citation??? Hmmm I will take some convincing!

Different horses for different courses springs to mind as does different techniques for different aircraft.

Pace

mad_jock

15th Oct 2011, 09:03

The reduction in AoA can be less than 1 deg its just enough to unstall.

And you are right an inadvertent stall is multiple cockups. Which is why I tend to bang on about attitudes and knowing what's going to get you into trouble. You should be able to see that your approaching the stall by looking out the window and the control feel without any reference to instruments.

Windsheer is a special case as we all know.

My types procedure is to purposely pitch to just before the stall, full power you play with the pitch to just keep the stick shaker occasionally going off and leave everything as it is. Which is significantly different to the stall recovery which calls you getting rid of any drag falp and gear ASAP. This for us would entail a pitch up of about 8 degrees from the approach attitude.

And the other stall which we are worrying about when the freezing level is low is the tail stall and the recovery for that is pull back and deselect what ever you have just selected. But to be able to spot you have a tail stall instead of a wing stall you have to know that your wing isn't stalled.

Pace I don't see any problems at all with the procedure you have been given. The nose on the horizon will mean there is a reduction in AoA but its just a limited max pitch down which is no bad thing. The amount of wellie is neither here nor there and is type dependent. What might be a ball hair on your type might be a fist full on others.

And your statement that this procedure is only for the older models leads me to suspect that the boffins at cessna have redesigned the wing to get rid of this feature of ball hair or huge other issues.

There has been quite large differences in certain procedures across the atlantic for quite a few years, the tail falling the airbus just after 9/11 started the process for the flight upset recovery but it still not there. There are still some FAA pilots that hold that you use boots full of rudder to lift the wing. Again in stalling we are taught as has been discussed but the FAA have taught to power out with less than 100ft.

With my Engineers hat on the FAA power out is crazy it relys on the fact that the pilot can't but help reduce AoA because of the forces involved and the aircraft wanting to unstall itself despite what the pilot does.

I can sort of see the point of minimal height lose when your landing configured from a fully developed, which to me gets into windshear training. But clean 200-300 ft is fine.

mad_jock

15th Oct 2011, 09:25

And you meantion stalling on departure how on earth are you going to power out of that.

You are already at max power your wings are over AoA you haven't got anything else to play with apart from reduce the pitch.

BEagle

15th Oct 2011, 10:30

How you can be so demeaning of examiners who have spent all their lives in the industry just because they happen to be FAA Looses me! One spent 10 years with the FAA accident investigation.

It wasn't me - it was the Boeing chap who told the meeting that the problem had arisen due to FAA examiners mis-applying the 'minimum loss of height' requirement as 'no loss of height' - hence the potentially dangerous 'TOGA and don't descend' nonsense which has spread across the industry. I also suspect that 'windshear go-around' techniques have been confused with stall recovery techniques by some.

This revised technique has now, I understand, been issued as a B737 requirement and also on Airbus aircraft. Certainly ba now use it on their B737 fleet.

Pace

15th Oct 2011, 10:44

Mad jock

I really think we are talking the same language. There are two ways! You are either going for the quickest way at all costs to break a stall or your going for minimal height loss to achieve that!
There is a subtle difference.
If you are at max N1 in the climb and stall you have to go for AOA reduction to get the wing flying as well as pitching for speed tapping into potential energy as you have no other option.
But isn't that what it's about? Different horses for different courses and being able to think out of the box!
Pitching strongly maybe fine at altitude where it doesn't matter whether you loose 100 feet or several hundred feet.
That may not be the case if terrain is a few hundred feet below.
We also have to consider that different aircraft have different behavior patterns so it partially about being familiar with your craft.
How many pilots do you know who are not speed aware, who stick flaps down above speed limitations etc ?
How many do you know who's strengths are not spatial awareness or being able to feel and sense what there craft is doing ?

Pace nb written on I phone

mad_jock

15th Oct 2011, 15:18

At no point has anyone here said pitch strongly just "enough"

And you don't have to tap into potential energy you just need to reduce your AofA which will reduce your rate of climb but it won't be required to decend. In fact recently this exercise was added into the UK syllabus as one of the set exercises.

As for not speed aware yes when they come online they are a bit ****e but we soon sort that out and usually its more wanting to shoot the approach at Vref + 30 or some such. As I said the only real time they can get anywhere near stalling is forgetting to power up on level off after decent. Aka the Dash crash in Colgan US. This crash is one of the reasons why the FAA is revisiting the FAA training on stalling. In the same way that the tail coming off the airbus has changed there views on controlling a flight upset. But the change is struggling to come through because there are so many folk out there keep going for this minimal height lose stuff and its very hard to teach old dogs tricks especially when they actaully believe that the new way is bollocks when it isn't.

As for the feel thing, as you well know there are pilots out there that have been flying for 40 years who appear to have relatively little feel for the aircraft what it is doing and little or no 5th sense about what the aircraft needs to sort itself out. Which is why I quite like your limit of nose to the horizon because its gives them something set to go for.

Pace

15th Oct 2011, 15:42

And you don't have to tap into potential energy you just need to reduce your AofA which will reduce your rate of climb but it won't be required to decend. In fact recently this exercise was added into the UK syllabus as one of the set exercises.
No you dont HAVE to tap into potential energy but effectively consider this?
Forget jets you are flying a small aerobatic machine you have full power but your climb is so steep that your speed falls off sharply.
Now the speed had dropped way below stall the nose falls! where are you getting energy from to get enough air moving over the wings? Just the engine?

I always think of an aircraft having two power sources and two throttles. One the conventional throttle the other the elevator which allows you to tap into the potential energy in the airframe.
How does a glider in still air with no lift and no engine break a stall?

Pace

mad_jock

15th Oct 2011, 15:59

We were taking about stalling on departure not an extra mid airshow. And it could very well be that the hot ship which has an airspeed of 0 isn't actually stalled, even though she is hanging in the air.

In fact instead of buggering about with FAA examinors why don't you just contact Cessna Citation support and get them to clarify what they mean in the manual. And to be honest if things have changed and it hasn't filtered down yet to the troops.

Pace

15th Oct 2011, 16:43

We were taking about stalling on departure not an extra mid airshow. And it could very well be that the hot ship which has an airspeed of 0 isn't actually stalled, even though she is hanging in the air.

Mad Jock

I know what you mean but this is a private pilots forum and as such with low time pilots we should discuss in full.

We talk about Jets as if they are somehow different to other aircraft.
The Airliner which ran out of fuel, all engines stopped glided onto a disused airfield the same with the 777 at Heathrow.

Something produced enough airflow for them to fly?

Had the Airline Gliding to the disused airfield decided to try and fly level it would have eventually stalled.
Would AOA on its own make it fly again where would it have got airflow enough to make the wing fly from?

This is getting silly and point scoring.

I am sure at my next renewal which will probably be in a sim feb next year I will be brought up to date.

Pace

mad_jock

15th Oct 2011, 17:02

I am not disputing the use of potential energy to aid in a stall recovery if so required. Just on the example you used you don't have to decend because you already have enough energy getting pumped in by the donks.

An aerofoil doesn't have a clue whats giving it energy, all that effects it, is the angle of attack it is to the airflow. How much air it requires over it to produce enough lift to support 1t or 5t or for that matter 300tons is a function of the design.

This is the issue of teaching "stall speeds" if everyone was just taught AoA from the start and for that matter flew on AoA for approches we could cut the amount of mis conceptions out there by 90%. We could also get rid of rafts of performance manual charts pissing about with different weights.

Please contact cessna and see what they say.

PA31flyer

15th Oct 2011, 21:46

The stall upon departure can be corrected either by 'tapping into potential energy ' or simply a reduction in AoA. Depends on the stall being due to a lack of airspeed or the aircraft exceeding the critical angle of angle and it still has airspeed.

Lemain

15th Oct 2011, 22:30

What is the reason that there is a possiblity of a wing drop during a stall?

I can only think of 1 reason:
Left & right wings are not 100% same (though in theory they are supposed to be designed that way, but nothing is perfect), and also the airflow at left & right wing might not be the same due to sideslip or wind or some other force of nature, therefore the wings might stall at slightly different time.

Do I score at least 90%?I assume you are talking about a single-engine propellor monoplane? Only one reply has mentioned prop torque. But it isn't just the torque (or should one really say 'couple') that is the issue. The most asymmetric thing that you'll find on the aircraft is the prop -- and that varies according to whether the prop is stalled, stopped, providing power, retarding airflow.... Without doubt, the largest single factor that affects which wing drops first is the prop; but it isn't simply a matter of 'torque'.

On recovery, torque comes into play (and the gyro effect) as any taildragger pilot knows only too well.

mad_jock

15th Oct 2011, 22:32

There is only ONE thing which makes an aircraft stall and thats exceeding the critical angle of attack.

The only requirement for tapping into potential energy is if there isn't enough power to over come the drag just prior to exceeding the angle of attack. Then you have to find energy to get the aircraft through that high drag part of the curve until the engine can produce more power than the aircraft produces with drag.

BEagle

15th Oct 2011, 22:34

Depends on the stall being due to a lack of airspeed or the aircraft exceeding the critical angle of angle and it still has airspeed.

I've heard everything now......:uhoh:

Crash one

15th Oct 2011, 22:40

Depends on the stall being due to a lack of airspeed or the aircraft exceeding the critical angle of angle and it still has airspeed.

The ASI reads through a line roughly parallel to the angle of incidence so if it still has airspeed in that direction it isn't stalled. If the AOA is exceeded the airspeed has bugger all to do with it. I think!
Jock will now kick my arse no doubt.

Lemain

15th Oct 2011, 22:44

There is only ONE thing which makes an aircraft stall and thats exceeding the critical angle of attack.I don't suppose anyone is going to take great issue with that....but it wasn't the question the OP asked.

Lemain

15th Oct 2011, 23:00

The ASI reads through a line roughly parallel to the angle of incidence so if it still has airspeed in that direction it isn't stalled. If the AOA is exceeded the airspeed has bugger all to do with it. I think!
Jock will now kick my arse no doubt.Yikes! It's a wee bit more complex than that particularly when you get to the edges of normal operational conditions (which a stall or spin is, of course). To keep the airframe 'flying' you need essentially non-turbulent airflow over the aerofoil surfaces. Wings, fuselage and tailplane/elevator. At a certain angle of attack (let's call it zero) the lift from the aerofoil surfaces equals the downward gravity force of the aircraft and load. As the aircraft gets heavier (more pax, fuel, baggage) the AOA needs to increase to match the downforce. That's fine all the while the airflow over the surfaces is essentially laminar. At some stage -- maybe low speed, an attempt to climb without power, engine output reduction (carb icing?) the airflow might become turbulent and the airframe approach a stall -- the pre-stall buffet due to non-laminar airflow. At this stage, in principle, the pilot can either push the stick forward to reduce the AOA, and increase airspeed or he can apply more power -- though the latter is dodgy if he is very close to a stall as he could end up in a power stall or power spin. It seldom happens presumably because it takes a bit of a clot to get into that position and clots don't often get licences? Darwinian principles tend to reduce the number of clotted pilots.

Pilot DAR

16th Oct 2011, 00:06

Hmmm, some not so accurate information is emerging....

Letting alone any discussion of jets,

in a C172 the right wing is actually at a slightly higher AoA than the left due to the fuel return, the fuel return on goes to the right

Not really. Both wings of a 172, like most trut braced Cessnas, can be indepedantly adjusted with cams, so as to change the angle of incidence. 172's (at least carburetted ones) do not have fuel returns. The 172S might, I'll have to enquire. A fuel return would not affect stalling characteristics. You will find that only the most precisely manufactured metal plane has both wings the same. Those minor variances will create wing drop in a stall. In small amounts, it is a non event. I have test flown aircraft where it was certainly unacceptably high though.

At some stage -- maybe low speed, an attempt to climb without power, engine output reduction (carb icing?) the airflow might become turbulent and the airframe approach a stall -- the pre-stall buffet due to non-laminar airflow. At this stage, in principle, the pilot can either push the stick forward to reduce the AOA, and increase airspeed or he can apply more power -- though the latter is dodgy if he is very close to a stall as he could end up in a power stall or power spin. It seldom happens presumably because it takes a bit of a clot to get into that position and clots don't often get licences?

I'm not in agreement with this either.

A quick list of factors which affect the stall "speed":

AoA (flap position can affect), weight of the aircraft, C of G position, G loading (angle of bank), and aerodynamic "cleanliness" of the wing.

Power affect where you are going while the stall is happening (up or down).

Speed, in conjunction with power will affect your AoA. Drag affects speed.

Aircraft (other than momentarily, on inertia) do not climb without power. Laminar vs turbulent airflowcan be an element of a stall, but turbulent airflow over much of the wing can still sustain lift enough to prevent a stall in some aircraft types (and most GA types).

Yes, pushing the stick forward reduces the AoA, and this important for preventing/recovering a stall, but the reduction of G loading is another important element. Other than speeds presented relative to angle of bank, stall speeds are presented in one G flight. It is possible to fly at less than one G for brief periods, and this could be an aspect of stall prevention/recovery. An aircraft flown at a half a G is still fairly controllable, and has a much lower stall speed. Obviously, you can't do this for long, but sometime, just long enough to get yourself out of trouble. This is a coupled effect with AoA reduction.

Applying more power changes your direction of flight (let's presume from a little downward to a little upward for ease of understanding). If nothing else changes (attitude relative to earth), the AoA has been reduced by doing this, and the speed will increase. Both of these will create an increased margin from the stall.

A wing will stall when its critical angle of attack is exceeded for the G loading. Though speed plays a role in this, if the G is not one, the speed may not have the direct relationship to the stall that a pilot expects.

"power stall" and "power spin"... Well... with the exception of control limited aircraft, any aircraft can be stalled and spun at any power setting. Power will affect this, and torque can certainly effect handling entering and recovering. Pilots are wise to seek out good training for this type of flying, and when competent, practice regularly.

Stall spin accidents are a result of the pilot failing to maintain flying speed for the conditions, but are not isolated to new or careless pilots. Unforseen conditions can lure a pilot in. The only way is for that pilot to use remarkable wisdom, and experience to avoid the condition - 'cause once you're there, it is what it is. Stall spin is too common, I have cleaned up some wrecks. The most common example of this is a floatplane departure from a lake, where once crossing shore in the climb, unfavourable wind, or downward moving air prevents a climb over the obsticle, and the pilot pulls back more in an effort to clear. This can become very bad fast, and only careful departure path planning is going to prevent it.

The circuit at a well used airport is a naturally safe place to fly close to the ground, as there are few surprises. Start flying planes close to the ground, away from airports, and the risks increase quickly. Stall spin is probably close only to CFIT as the greatest risk.

Do not assume that because you are a "good pilot" you cannot find yourself approaching an unexpected stall (which puts you at risk of a spin). All planes will warn you in feel (some earlier than others). only lots of practice will teach you to feel the plane's approach to a stall.

"Good" (non Darwinnian) pilots have learned (so far, anyway) to anticipate those conditions, leave themselves an out, and are current with the handling of aircraft they are flying, in that regime.

mad_jock

16th Oct 2011, 00:17

Well in my opnion the reason why wings drop has got nothing to do with the most of the discussion its pure and simple pilot error. Most pilots have to go and annoy the poor aircraft and upset it.

When I first started instructing in tommys I had a wing drop every time. A year and a bit later and 900 hours they didn't drop a wing. Same airframes. So I can only conclude it was me being cack handed or cack footed. Give it to the students and it used to drop a wing again (much to thier disgust).

And yes crash one a kick up the arse is required. Its all to do with flow over the aerofoil and when the boundary layer becomes unstuck. Although I would slightly disagree with the turbulence comments because sometimes the engineers induce it with vortex generators because it delays the boundary layer becoming unstuck.

The best way to have a play with this is take a piece of card and get some one to drive down the road and have a feel of the forces required to hold it at various angles to the airflow sticking it out the window. If you can get hold of an aerofoil profile even better. As you go from flat lifting the front edge and droppping the rear you will feel an upwards force and a small rearward and when you go too far it will disappear and be replaced by a relatively large force in the opersite direction to the direction of travel. Once you lower the front again it will go back to an up force with a bit of rearward force.

Go have a play with it, its much more intuative if you can see and feel whats going on.

Crash one

16th Oct 2011, 17:25

And yes crash one a kick up the arse is required. Its all to do with flow over the aerofoil and when the boundary layer becomes unstuck. Although I would slightly disagree with the turbulence comments because sometimes the engineers induce it with vortex generators because it delays the boundary layer becoming unstuck.

OK I'm sorry I didn't go into all the minute detail of laminar flow separation, boundary layer turbulence & vortices.
Anyway I do think there is more to it than saying stalls are caused by pilot error. Of course they are, either in error or on purpose but they have always been caused by the pilot.
I seem to remember a gliding instructor flying a high performance laminar flow piece of tupperware at 3000ft when it started to rain, 10 mins later he was standing in a field thinking "what the hell was that about". Parasite drag?

Pull what

16th Oct 2011, 18:24

Pace--I think you are confusing a recovery from the approach to the stall with a fully developed stall.

This is the updated Airbus information.

http://xa.yimg.com/kq/groups/10483604/2002517561/name/Updated%20Stall%20Procedure.pdf

This is the important bit

The priority is reducing the angle of attack. There have been numerous situations where flight crews did not prioritize this and instead prioritized power and maintaining altitude. This will also address autopilot induced full back trim.
(http://xa.yimg.com/kq/groups/10483604/2002517561/name/Updated%20Stall%20Procedure.pdf)

mad_jock

16th Oct 2011, 21:35

No mate it was the wing drop I was on about.

I thought they always dropped as well until I realised I had stalled the same tommy about 15 times and it hadn't wing dropped. Next time I demo'd it I did one as normal and one annoying it. The one where I annoyed it had a wing drop.

The likely hood is though that if your not expecting it you will annoy it so therefore you will get a drop.

But it doesn't have anything to do with where the ASI is pointing the Crit AoA stays the same.

mad_jock

17th Oct 2011, 08:00

And thinking about it with a tommy its proberly designed like that.

Ie its a feature of the tommy to bite back if you don't do it properly.

Pace

17th Oct 2011, 12:21

Pull what

I have thousands of hard weather hours mainly in piston twins and singles and am very aware of conventional stall recovery!
I would go further and consider my strengths as a handling pilot ( I can get other ppruners who have flown with me 2 who I gave Citation SICs to)
I don't disagree with you BEAgle or Mad Jock as that is my stall recovery instincts too.
The method taught by 3 FAA examiners leans more to power/ thrust and maintaining altitude relying on power and a very gradual reduction in AOA.
The CItation is an above wing engined jet which naturally reduce AOA on application of max thrust so maybe that is part of the reason ?
I know when I accidentally reverted to my instincts and recovered as I would do a Seneca twin I got my knucles rapped and saw with my own eyes a large loss of altitude.
Mad Jock made a valid point concerning a max N1 stall in the climb and appeared to take offense at tipping the nose not only to reduce AOH but to tap onto airframe potential energy for more airflow!
Contrary to his argument against power and maintaing altitude ?
BEAgle considers any FAA examiner to be an idiot who should be shot at dawn ; )
Many heavier jets have used power recoveries! Ok maybe things are changing and I would like to know the recommendations for the CITATION with this new recovery approach as i have seen the large height loss with a standard recovery ? I don't really disagree with much of what any of the three of you have said

Pace

chubbychopper

17th Oct 2011, 13:33

The sim excersise that is being referred to does not require the student to recover an aircraft that has actually stalled. The recovery should be effected at the FIRST SIGN of an impending stall, be this stick shake, aural warning or aerodynamic buffet.

In many jet types it is indeed possible to recover PRIOR to the stall with zero or a very small loss of height. The outcome will be dependent to some degree on pilot handling, and how close to the critical angle the aircraft gets prior to the natural or artificial warning. If there is a good margin, you have a good chance of achieving zero loss of height.

Pace, you have referred to the Citation's high mounted powerplants. This is an old chestnut that has little or no relevance when discussing stall recovery in a jet aircraft. Consider the situation as you approach the stall in your Citation with a low value of N1 set (arguably a common lead up to a real life stall situation). Your technique of simply adding power will not on its own effect any immediate change to the angle of attack due to the time required for the engines to spool up. (they too are operating at an increased AoA). Similarly, if you are foolish enough to find yourself approaching to stall with a high power setting, any small addition of thrust is hardly likely to make a jot of difference. In either event you would be well advised to reduce the angle of attack by use of forward elevator. This will lead to a reduction in lift, and an inevitable loss of altitude.

By all means add as much thrust as you wish, but a change of angle of attack is highly desirable, and elevator is going to do it for you first.

Pace

17th Oct 2011, 14:13

Chubbychopper
I don't disagree with what you say! The stall recovery maybe at incipient where the wing is still flying and at an AOA which is condusive to flight.
As I posted earlier incipient is flavor of the month in training schools but unreal.
The difference bet
Ween incipient and full can be very small you cannot have procedure A for incipient recovery and procedure B for full! That's a joke!
You have to have a recovery method to cover the whole?
Obviously any recovery has to include a reduction in AOA whether in minute gradual amounts or a full bloodied push forward for a large AoA change and a push for potential airframe energy too.
The Citation is recovered in a different way to a PA34 recover it like a PA34 and the VSI will be heading down at a fast rate.
With the new recommendations I prob do need to speak with Cessna

Pace

chubbychopper

17th Oct 2011, 15:45

I am not familiar with the term "incipient stall." An airplane is either stalled, or it is not. I assume you mean "approaching the stall, or an "impending stall."

Yes, jet training facilities do emphasize recovery from the approach, or first recognition, of an impending stall. This, in my humble opinion is what they should teach. It just so happens that if the aircraft does actually stall, the recovery action is the same.

That's all for me on this thread.

BEagle

17th Oct 2011, 16:11

BEAgle considers any FAA examiner to be an idiot who should be shot at dawn ; )

If you'd bothered to read what I posted, I said that SOME FAA examiners had been misinterpreting 'minimum loss of height' for 'no loss of height'. Hence the utter stupidity which has led to the requirement to reteach stalling. The information came directly from a senior American Boeing representative who clearly does understand.

No-one is suggesting that a large pitch attitude change is needed to reduce AoA, just that a sufficient attitude change is made. That will not cause a massive RoD unless it is grossly mishandled.

mad_jock

17th Oct 2011, 19:16

Pace mate I didn't take offense. I always have it mind when two pro's are debating a point especially in this forum that there are always a large number of inexperenced reading our words and taking them to heart.

I didn't want any student or for that matter low houred pilot recovering from a departure stall by hoofing the nose down into a decent.

Pull what

18th Oct 2011, 11:28

This is the latest from the Airbus chief test pilot

The AoA decrease may be obtained
indirectly by increasing the speed,
but adding thrust in order to increase
the speed leads to an initial adverse
longitudinal effect, which trends to
increase further the AoA (fig. 4).
It is important to know that if such
a thrust increase was applied when
the aircraft is already stalled, the
longitudinal effect would bring the
aircraft further into the stall, to a
situation possibly unrecoverable.
Conversely, the first effect of reducing
the thrust is to reduce the
AoA

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

In summary:
FIRST: The AoA MUST BE REDUCED.
If anything, release the
back pressure on stick or column
and apply a nose down pitch input
until out of stall (no longer have
stall indications). In certain cases,
an action in the same direction on
the longitudinal trim may be needed.
Don’t forget that thrust has an
adverse effect on AoA for aircraft
with engines below the wings.
SECOND: When the stall clues
have disappeared, increase the
speed if needed. Progressively
increase the thrust with care, due to
the thrust pitch effect.
In practice, in straight flight without
stick input, the first reaction
when the SW is triggered should be
Relative airflow
Relative airflow Thrust increase
Relative airflow
Thrust reduction
Figure 3
Pitch control
is a direct
AoA command
Figure 4
Adding thrust
leads to an
increase in AoA
Figure 5
Reducing thrust
leads to a
decrease in AoA
to gently push on the stick so as to
decrease the pitch attitude by about
two or three degrees in order to decrease
the AoA below the AoA SW.
During manoeuvres, the reduction
of the AoA is generally obtained
just by releasing the backpressure
on the stick; applying a progressive
forward stick inputs ensures a
quicker reduction of the AoA.
If the SW situation occurs with
high thrust, in addition to the stick
reaction, reducing the thrust may
be necessary.
10. Procedure
As an answer to the stall situation,
a working group gathering the FAA
and the main aircraft manufacturers,
including Airbus, ATR, Boeing,
Bombardier and Embraer, have established
a new generic procedure
titled “Stall Warning or Aerodynamic
Stall Recovery Procedure”
applicable to all aircraft types.
This generic procedure will be published
as an annex to the FAA AC 120.
This new procedure has been established
in the following spirit:
q

mad_jock

18th Oct 2011, 13:29

Come on Pace has said that he is going to check with cessna

Anyway it seems at last someone has grabbed the bull by the horns and is publishing a best practise which will hopefully cut all the different interpretions of the current methods.

Pilot DAR

29th Oct 2011, 20:50

This Youtube clip provides a useful demonstration of wing drop during a stall.

Float Plane Takes A Nose Dive! - YouTube (http://www.youtube.com/watch?v=mhyURC8faQY&feature=related)

This stall was destined to happen at just about the point where the pilot entered the left turn. The pilot forgot how much drag increase there would be with the turn, made worse by the very small radius of the turn (brought about by the choice to turn in such a confined area).

This video clearly demonstrates several things:

A wing can drop during a stall - but we knew that...

Turns cause lots of drag increase.

An attempt to land from a non stabilized approach can turn out badly,

And, the impossible turn. There was some discussion about the impossible turn recently in another thread on the instructors forum, but the whole thread spun in.

This pilot attempted the equivalent of a turn back, though, with lots of power. All other things about what this pilot attempted were the same, as could be foolishly attempted after an engine failure close to the ground after takeoff. Low speed and altitude, and, 180 degree heading change in a small radius. This pilot intended this turn, and the only surprise (as opposed to a sudden engine failure) was that the aircraft simply was not capable of this, in the space available.

If, the pilot had not stalled and dropped the wing, at the altitude he did, he surly would have arrived at the water stalled, with no ability to arrest his rate of descent. There was just no lift or energy left in the aircraft. Had the plane been very light, and lots of power had been applied, things might have turned out better, but still, maybe not....

The left wing dropped, perhaps because it stalled, or perhaps due to a whole bunch of power being added, causing torque, which the lift of the wing, and aileron (with co-ordinated use of the rudder, of course) could not counteract.