Wing drop during stall

[Pace]

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]

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]

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]

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]

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]

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]

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
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]

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.

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]

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]

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 and click on 'Presentations' - then view the one on stalling.

[frontlefthamster]

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]

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]

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]

Originally Posted by Pull what

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]

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]

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]

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]

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]

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]

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.