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High altitude stall recovery B737

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High altitude stall recovery B737

Old 19th Feb 2018, 15:19
  #61 (permalink)  
 
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Pirate Pete,

Are we talking about a stall or an “approach to stall” where buffet begins, IAS numbers go red, etc? Big difference.
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Old 19th Feb 2018, 15:55
  #62 (permalink)  
 
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GF,

Not any more - there is just one procedure now for both.

"The traditional APPROACH TO STALL training is characterized by
a controlled deceleration to stall warning, followed by a power
recovery with minimum altitude loss
• The difference between an APPROACHING STALL and an
ACTUAL STALL is not easy to determine, even for specialists
• In numerous accidents, the APPROACH TO STALL procedure
was applied whereas the aircraft was actually stalled."

http://www.ukfsc.co.uk/files/Safety%...une%202010.pdf

"Approach To Stall Recovery
A single procedure has to be defined
focusing on AoA reduction

• Classical Approach to stall procedure focuses:
On thrust application
Minimum loss of altitude
• It is NOT appropriate for EVERY stall condition:
Possible inability to reduce AoA with the TOGA thrust
application
Recovery may require thrust reduction
Recovery from a stall may require altitude loss."
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Old 19th Feb 2018, 16:11
  #63 (permalink)  
 
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Originally Posted by piratepete View Post
Gents.You cannot solely consider the issue of stall recovery from the position of "high altitude".In a comprehensive pilot training module for this very serious issue it is quite important that pilots of modern jet airplanes are trained in both "terrain is a factor" also when it is not.The recovery methods necessarily differ.This can be life or death.
What's different? Why is it any less important to unstall the wing at low altitude, than it is at high altitude? Again, if terrain is a factor then unstalling the wing ASAP is the only action that will give me a flyable wing and any chance of pulling out and away from that terrain.

Many TRIs emphasize that minimum altitude loss is the key to a "correct" recovery.
And incorrectly so, with the trail of carnage to show for it. At both low and high altitude.

Sometimes powering out is the better method, of course at altitude primarily unstalling the wing is correct technique.Have an open mind Sir.
There is actually no such thing as "power out" of a stall. It goes much further than being bad technique, it doesn't exist. It's a fundamental misconception.
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Old 19th Feb 2018, 17:59
  #64 (permalink)  
 
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High Altitude stalling is always a consequence of poor energy management, that is to say flying in the "T" thrust limited zone or "B" Buffet limited zone with a lack of situational awareness for the conditions, perhaps without the benefit of real time bank angle protection( No LNAV) or flying to close to "maximum" and then hitting turbulence or increasing warmer air and basically not descending, or limiting the bank. Mr Boeing,bless him says:

STALL RECOVERY.
In all upset situations, it is necessary to recover from a stall before applying any other recovery actions. To recover from the stall, angle of attack must be reduced below the stalling angle. Nose-down pitch control must be applied and maintained until the wings are unstalled. Under certain conditions, on airplanes with underwing-mounted engines, it may be necessary to reduce some thrust in order to prevent the angle of attack from continuing to increase. Once unstalled, upset recovery actions may be taken and thrust reapplied as needed.
Ref: Aerodynamic Principles of Large-Airplane Upsets
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Old 19th Feb 2018, 18:40
  #65 (permalink)  
 
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In this thread there has been a confusion in the discussion by some people advocating the recovery from approach to stall and others answering with recovery from full stall techniques; and vice versus. Some back & forth has not been apples & apples, hence some agitation. If the topics were separated then perhaps clarity would prevail.

IMHO the only opportunity power might be used to aid recovery is if the wing is not aerodynamically stalled. I can't see how brawn can overcome brains.

Many TRIs emphasize that minimum altitude loss is the key to a "correct" recovery.

I doubt SFI/TRI/TRE's made the rules. Was it not that they were instructed by XAA's to do so? If so, where did the error lie?

The bit about 'ground contact being a threat' always tickled me. Having been a crop sprayer being close to the ground meant 'at most times on the job', without hitting it. i..e 3-5m depending on the application. Doing pipeline surveillance it could mean 200-500' as allowed.
Recovery from approach to stall at 500' on finals full flaps IMHO does not mean maintaining 500'; it means recovery from your predicament without hitting the ground, and not making it doubly difficult by entering a secondary stall, which often meant you stood a better chance of doing so. It was a delicate manoeuvre where low kinetic energy needed to be increased and if there was some potential, energy to help you do so, why not use it with finesse? Do you fail the tick in the box if you recover and fly away safely at 200' from 500', or must you achieve the same sweating success above 400'? In real life they both pass.
At 200' the dices are loaded and more delicacy & finesse are required. In the days of real training in the sim it was nice to do both, and the crews loved it. Sadly time has been stolen from real training.

When Boeing FCTM said "recovery from stick shaker (low level) was apply thrust and reduce attitude" I interpreted that not as apply thrust 1st then reduce attitude; I considered it as both at the same time, and if the student pressured the elevator before thrusting the levers by a split second there was no admonishment. But if they did it the other way round, and secondary stalled, there was.

It's taken a longtime but I think common sense has woken up a little; not enough. Why should there be only one size fits all? We have other recall procedures that need quick decision making; we are supposed to be intelligent trained professionals. Or is this one size fits all a reflection on what the opinion is of the standard of professionals. Only time to think of one thing, when as a pilot we should be able to choose the best applicable. IMHO.

With that question I lump the new Unreliable Airspeed procedure introduced a few years ago. It took 2 minutes and 8 check items to tell me what I already knew to do; by which time the a/c had transitioned from its last steady state and needed to be returned to it. That has been discussed previously, and I don't which to open that debate. I think the debate is much deeper about the true depth of professional pilot training and what is expected of us.

I've run out of tin hats.
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Old 19th Feb 2018, 18:40
  #66 (permalink)  
 
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"Aerodynamic Principles of Large-Airplane Upsets"
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Old 20th Feb 2018, 00:05
  #67 (permalink)  
 
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If you are in the "approach to stall" and near the ground then powering out can be ONE option.If you are near the ground and FULLY STALLED you are basically finished.However at altitudes a long way from the ground then YES there is only one correct method.Unstall the wing, thats about it except watch out for other aircraft especially in RVSM.
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Old 20th Feb 2018, 00:09
  #68 (permalink)  
 
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Vesspot.
I dont know your background but for years and years TRIs have been teaching incorrectly that your performance in an approach to stall exercise was to POWER OUT with minimum loss of altitude.Of course this is wrong and could be fatal.I hope this has stopped but STILL hear of it being taught this way.
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Old 20th Feb 2018, 04:43
  #69 (permalink)  
 
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Piratepete, the point we're trying to make is that regardless of altitude, there is only one way to recover from a stall, and it has nothing to do with power.

As someone pointed out earlier, even the flight test engineers sometimes find it difficult to say when the actual stall takes place- and they're deliberately doing it. Throw in the startle factor of the crew that stalls inadvertently, and the less than accurate sim representations, would you risk treating it as an approach to a stall?

We accept that if you're close to a stall, then you can probably power your way out of it. That's pretty much a rejected landing, or low level GA.

The reason we're here trying to show you the difference is because there have been many crews who were improperly trained to maintain altitude, and that training simply gets them into more trouble when poop really hits the fan.
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Old 20th Feb 2018, 06:08
  #70 (permalink)  
 
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In real life they both pass.
At 200' the dices are loaded and more delicacy & finesse are required.
I agree with your general point. And so I would argue that you’d require more finesse to recovery at 400’!

By recovering at 400’ you’re riding a fine line between unstalling enough to be effective while not entering a secondary stall but also recovering from the altitude loss sooner. In this case, you’re closer to stalling AoA which is why I’d argue it requires more finesse.
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Old 20th Feb 2018, 10:39
  #71 (permalink)  
 
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There are also times when pilots have to that rare of tasks calling piloting.


But I do wish ATC would have shut up.
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Old 20th Feb 2018, 13:25
  #72 (permalink)  
 
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Let's take real life situation. Even at low altitude what does one do when the stick shaker sounds? Off course without thinking push the nose down. Everything else comes after that.
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Old 20th Feb 2018, 14:02
  #73 (permalink)  
 
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At altitude you’re not ‘powering out’ of a slow speed event. Decades ago the Captain slowed to FMC holding speed number at FL390 despite my comment “I don’t think we’re supposed to be this slow.” His reply “it’s ok, I’ve done it before.” No buffet. ATC said “normal speed” and power went to continuous where it basically had already been. Stuck. Zero acceleration. We had to descend. Captain “I don’t know why it didn’t work. It worked last time.” I asked “how heavy were you and what altitude?” “I don’t remember.”

25W brain in a 100W world.
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Old 20th Feb 2018, 14:17
  #74 (permalink)  
 
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Originally Posted by vilas View Post
Let's take real life situation. Even at low altitude what does one do when the stick shaker sounds? Off course without thinking push the nose down. Everything else comes after that.
The nose doesn’t have to go down as much as at least have a slight reduction in back pressure. Minor unloading has a big effect on AOA. Even at .95 G, which is barely noticeable, the plane will fly at less than it’s expected stall speed.

On the 727 it wasn’t a shock to get stick shaker if you were flying at the minimum flap speeds, especially while turning even using the increased minimum flap speed required while turning. Slight roll out, or slight back pressure reduction, and the stick shaker stopped. Completely unnoticeable by passengers.

At low altitude, in normal flight attitudes, minor AOA excursions require minor adjustments. At altitude, with more significant AOA/speed excursions, the airplane will need large corrections in AOA with resulting larger pitch changes.
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Old 20th Feb 2018, 14:18
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One time I saw power overcome aerodynamics. It was a Sukhoi 29S do a torque roll. Until then I think, in our type of a/c, I play by the law of physics and aerodynamics. KISS>

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Old 20th Feb 2018, 15:06
  #76 (permalink)  
 
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Originally Posted by RAT 5 View Post
One time I saw power overcome aerodynamics. It was a Sukhoi 29S do a torque roll.
Just to be clear, the video link shows a radio-controlled model, not a full size aircraft.
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Old 20th Feb 2018, 15:45
  #77 (permalink)  
 
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THREAD DRIFT - Low level stalling.
The AMS 737 accident investigation makes some interesting observations.
Note the pre publication comments to the Dutch Safety Board’s report - Appendix B. NTSB and Boeing comments starting on page 140 show just how a manufacturer will hang an operator out to dry in the event of an accident (even the absence of a comma). Boeing sates that the recovery was feasible with normal procedures.

Appendix M, page 201, gives the results of the Dutch simulator tests.
From a normal approach, a recovery from stick shake was possible within 450ft, but this depended on timely thrust application and the ‘correct flight technique’, which appeared to be maintain PLI.
“During the manual recovery, under the above given conditions (pre accident scenario), it was necessary to push the control column fully forward in order to prevent the pitch value from becoming higher than the pitch limit indicator leading to aircraft stall. As the recovery progressed it was not always possible to maintain the aircraft pitch at or below the pitch limit indicator without trimming the stabiliser in most cases, but adequate elevator authority was available for at least 40 seconds before trimming was required. Control forces were maximum between 30-50 pounds and such that with one hand full forward control column deflection was possible. Evaluations of various recovery techniques showed that timely application of thrust could ensure recovery after stick shaker. In the event that thrust was not applied within a few seconds of stick shaker, the airplane could still be recovered by making control inputs to prevent the airplane from stalling.”

A full stall recovery:- “Boeing test flight data demonstrated that once the aircraft had stalled, the minimum loss of altitude required to restore the (un?) stalled condition was approximately 500 to 800 feet. When the aircraft stalled, the remaining altitude of approximately 400-450 feet was not sufficient to restore the situation. (page 203)

Appendix N, page 205, provides interesting comparisons of pilot awareness and reaction time in similar situations - much longer than assumed by Boeing; also the surprising number of previous events.

http://reports.aviation-safety.net/2...738_TC-JGE.pdf
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Old 20th Feb 2018, 18:11
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Originally Posted by Stuart Sutcliffe View Post
Just to be clear, the video link shows a radio-controlled model, not a full size aircraft.
Which also plays by the same physics that a full size aircraft does, and the same physics that a C172 does, and the same physics as a B747 does, etc.

Physics doesn't change - the conditions do.

This is partly in response to RAT 5 as well.
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Old 20th Feb 2018, 19:10
  #79 (permalink)  
 
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Just to be clear, the video link shows a radio-controlled model, not a full size aircraft.

Mea Culpa. You are correct, sir. I hate being dumb, so try this.

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Old 21st Feb 2018, 13:06
  #80 (permalink)  
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From a normal approach, a recovery from stick shake was possible within 450ft, but this depended on timely thrust application and the ‘correct flight technique’, which appeared to be maintain PLI
And the correct flight technique certainly does not include selecting Flaps 15 when going around from Flap 40 at stick shaker
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