Wing drop during stall
 

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%?

Yes you have got it correct.and you actually mentioned more than one reason.

A wing stalls because the angle of attack of the airflow to the wing exceeds the value where the airflow can stay smoothly attached to the aerofoil and becomes turbulent with a subsequent loss of lift. as you say, one wing may be rigged slightly differently, the aircraft may be yawing, or turning, there could be slipstream effects etc.

( I also note from one of your other posts you say you are a flight instructor, so you should be well aware of the reasons why!)

Even the left/right displacement of weight in the aircraft may make a difference. Reason why some side-by-side seaters show marked different flight characteristics when flying them solo. Fuel inbalance might also be a cause of this.

Let's not forget the prop. torque

There will be differences between the wings - nothing is manufactured perfect, flies do not die symmetrically on each wing (particularly given that the propwash is asymmetrically), the odds of managing exactly zero sideslip is roughly zero, lateral CG won't be exactly central, and there may also be a bit of asymmetry in the tail.

There are different types of stall, but if:

(1) The stall is marked by mainplane flow separation, and
(2) One wing, due to the asymmetries above stalls a significant time before the other, and
(3) The flow separation starts near the tip (rather than near the root).

Then you are likely to get wing drop at the stall.

G

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.

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.

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.

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

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

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

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.

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.

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!

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.

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?

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.

"Weeeeeeeeeeeeeeeeeeeeeeeeeeeee!" is almost obligatory :ok:.

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

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.

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....

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

(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.

@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).

I thought I was wrong, but I was mistaken....
 

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

I guess we'll both live and learn PW!

!!!! 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

Yeah I'd be interested to find out too.

I was taught these together as "centralise". Meaning stick and rudder neutral.

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.

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

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...?

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).

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:

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.

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."

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).

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.

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....

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.

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

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.

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

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