steep turn wing drop question

[aviationcynic]

Probably an easy question, but why when stalling an aircraft in a steep turn, would you have a wing drop towards the top wing instead of the bottom wing?
My reasoning says it should be the inside wing that stalls first, due to holding off bank with aileron.

Any good explanations out there??

One text book I have glossed over it by saying "Either wing may drop regardless of the direction of turn, but generally a slight sideslip angle predominates just prior to the stall, causing yaw opposite to the direction of turn, and this leads to the higher wing stalling first." (Flight Instructors Manual, R.D. Campbell)

I can't quite grasp that for as far as I know the inherent directional stability of the aircraft would cause a yaw in the direction of the turn, due to sideslip, not in the opposite direction.

[mad_jock]

Outside wing stalls first. Because it reaches the critical angle of attack first.

This was demonstrated to me by my FII in a cessna, resulted in a rather novel way of flicking into a spin in the oppersite direction to the turn.


Haven't been brave enough yet to try to reproduce this effect in the Tomahawk.

MJ

[Flyin'Dutch']

Depends on whether the turn is descending or climbing.

FD

[Hilico]

This is from 1978, but I hated stalling and read very thoroughly to make sure I understood. Birch and Bramson say the alpha on the outside wing is always greater in a turn, therefore it stalls first.

Bit of a relief as we always came back towards level, rather than tucking under.

[aviationcynic]

I like the FlyingDutch response.

I probably should have clarified that I can explain why in a climbing turn the outside wing will stall first. ie the angle of attack is higher for the outside wing as it is travelling a greater distance yet gaining height at the same rate. (I'd draw a diagram at this point but it will be too tricky here.) The outside wing will therefore achieve the stalling angle before the inside wing.
However, this explanation and my corresponding diagram can not be transferred to a level steep turn concept.

I'm currently undertaking training for my instructor rating, and I've been told this is a common question during our test here at our club.

[Oktas8]

From experience, tend to agree with RD Campbell (what a great book).

Remember that directional stability means the aircraft tends to yaw into a slip. This means the slip has to exist before the aircraft will yaw: in a steep turn with a bit of rudder laziness, the aircraft will be slipping in the direction of the turn, directional stability never quite removing slip altogether. Since the aircraft will generally be slipping into the turn, the upper wing will tend to stall first.

*generally inserted to allow for the case of a high power setting / low speed causing yaw to the left, regardless of direction of turn.

Also pilots stalling in a steep turn commonly do so due to a low airspeed rather than high load factor, and if this is the case they may try to instinctively maintain the correct attitude with rudder instead of reducing bank or adding back pressure. This will also contribute to slip.

O8

(Edited to add the bit about rudder misuse.)

[Dan Winterland]

But in a balanced turn the higher wing will travel furhter therefore having a reduced angle of attack. (Just thought I'd complicate the arguement ):E

In my experience it depends on lots of things. Does the wing have wash out or wash in? Is the aerofoil symetrical throughout the span? Has the aircraft been bent in the past? Does slipstream have an effect?

Of our club aircraft, two have 23,000 hours or more. They are in very good condition considering, but they do not dispaly uniform stalling characteristics. Another type I instructed on always rolled in the direction of engine rotaion. Another type always dropped the lower wing, another always rolled wings level. And one glider I had the misfortune to fly always entered a spin if the wings weren't level at the stall!

Try it and see, don't rely on the theory as it often fails to oblige.

[aviationcynic]

There seems to always be some jump of logic in every one answer that I have seen (both here and people I've spoken too).

Some people say the outside wing will have a higher angle of attack, others say the outside wing will have a lower angle of attack because its travelling faster.
I believe that the outside wing will have a lower angle of attack because of the outside aileron being deflected up due to having to hold off the bank.

So could the people who've said the outside wing will have a higher angle of attack please give any reasoning to support this statement?

[Hilico]

Dan Winterland has a point; the school I learned at had two C150s and I always favoured one for spin/stall lessons because it was so much more tame.

As to the explanation of why the alpha on the outside wing is more, I've forgotten, and the book I read has probably mildewed into a solid lump. If I can find it and prise the leaves apart, I'll get back to you.

[inbalance]

Someone sayed: " I believe that the outside wing will have a lower angle of attack because of the outside aileron being deflected up due to having to hold off the bank. "

That depends on the Type of Aircraft and the Maneuver flown. Lot´s of Aircraft don´t need oposite aileron during turns and some need aileron into turning direction to hold the bank.

But think about this:
"As the airspeed bleeds off, you will need to apply more and more right rudder to maintain coordination ( to compensate for the helical propwash). Coordination is very important, because even a slight slip angle will cause one wing to stall before the other. This could easily result in a spin, and even if you don't get a full-blown spin, the sudden change in bank angle is pretty unpleasant.

Also, in this high-power low-airspeed situation, you will need to apply steady right aileron (to compensate for the rotational drag of the propeller). Note that the roll damping goes to zero at about the same point where the stall occurs, so you will need to intervene rather actively to keep the bank. The standard advice applies: make sure you use the ailerons and rudder together. Because the airspeed is low, you will need a whole lot of rudder deflection to coordinate with a small amount of aileron deflection, and indeed right near the stall you can quite nicely control the bank angle using the rudder alone. Imagine that the left wing is about to stall. By stepping on the right rudder pedal, you can swing the nose to the right, causing the left wing to speed up and become unstalled. During this maneuver, you might want to lower the nose a tiny bit, so the right wing, which is swinging backwards, doesn't stall."
by John S Denker, see how it flies


I think most of those wingdrops during turns are caused by improper coordination.

[poteroo]

Out of balance = Out of luck!

Fully agree with Inbalance, (previous post).

The stall which occurs when the lower wing is lifted by aileron, (to improve ground view), in a steep, powered turn is known by several different names:

In Canada - it's the 'moose stall'
In Australia - the 'mustering stall'

Low speed maneouvring requires very strong yet exact rudder inputs. Not enough emphasis on rudder in PPL course.

Types with reserve power can usually be recovered easier, because there is continuing rudder command as power is increased in the turn, or when the stall warning comes on. My experience is that a 172 will get out of trouble better than a 150, and so on.

cheers,

[Oktas8]

Regarding co-ordination & rudder (mis)use in turns-

Once upon a time I had access to a fairly good simulator for pre-solo training. Well, initially I thought "What's the point? Simulators are for IF training not pre-solo!", but then I discovered that the programmers had made the rudder far more sensitive & powerful than any real aircraft I've flown.

Cutting a long story short, my students that year were really really sharp when it came to rudder use!

So since then I've regretted not having access to a good visual simulator for ab-initio training.

No, MS Flight Sim doesn't count - no control feel. :sad:

[kabz]

From the FAA training materials ...

In coordinated flight, the aircraft will stall straight ahead, even in a steep turn.

In uncoordinated flight, a slipping turn will cause the outside wing to stall first, and the aircraft will go over the top.

A skidding turn will have the inside wing stall first and the aircraft will stall-in.

It kind of seems like the effects of the outside wing flying a teeny bit faster, etc., seem largely to be disregarded, in comparison with the larger effects of uncoordinated flight.

Disclaimer: ~I have never tried this~
It was kinda annoying to realise that no-one has ever showed me any of these manouvers. Hehehe, maybe I can grab an hour in the Decathalon and have a play ... :E

[BigEndBob]

Has it anything to do with wing loading.

Try power off steep turn to stall in balance.
Straight stall, possible fall into turn and recover.
Try same again with full power. Result buffet little height loss.
Most instances recovery is to relax back pressure.

Now, repeat full power, steep turn, imagine slipping in, apply top rudder, rudder causes roll opposite to turn, which is then offset with more down aileron on out side wing, greater AofA ,more loading, snap stall, the rest is very interesting.

If kept in balance, other than for wing damage/mismatch, it will probably always stall straight. But then.......

How many demo. steep turn with flap. Far more comfortable.
In Warrior/Archer set power, <Vfe, 45 AofB, set 2nd flap and it will go around all day with very liitle back pressure or 'G' force?
How much back pressure does it take to stall?