High altitude stall recovery B737

[Centaurus]

We know that if a high altitude stall occurs for whatever reason, the initial action is to level the wings and lower the nose; thus reducing the angle of attack. Simultaneously thrust is applied. For 20,000 lbs thrust CFM 56 engines at 37,000 ft the thrust available is about one quarter of that at sea level and the pitch up from thrust application is easily countered. Different of course during a go around at sea level

Once recovery from the stall is made (almost instantaneously if the angle of attack if reduced sufficiently and promptly) the question arises what minimum safe airspeed should be attained before the pilot eventually aims to level out? To quick a level out after stall recovery at high altitude invites secondary stalls as evidenced by continued buffeting. The Boeing FCTM does not address this clearly, especially as the pilot may be tempted to prematurely initiate levelling out for minimum height loss.

One clue may be found in the FCTM under Chapter 4, Climb, Cruise, Descent and Holding where in part, it states the following:

"Recommended holding speeds can be approximated by using the following guidance until more accurate speeds are obtained from the QRH.
Above FL250, use VREF 40 +100 knots to provide at least a 0.3 g margin to initial buffet (full maneuver ability)"

This suggests that once the airspeed reaches approximately 230 knots (depending on weight of course) during the course of recovery after lowering the nose, it would be safe to stop further descent and review the situation from there. It follows that if the stall was the result of mishandling due to severe turbulence and this severe turbulence was still present during the recovery process, the recovery to level flight should be delayed until reaching severe turbulence optimum penetration speed.

This recovery technique when used in the simulator results in a height loss of approximately 3500 feet. If using optimum severe turbulence penetration speed as the aiming point before recovery to level flight, then a height loss of approximately 5000 ft is needed.

Constructive comments welcomed.

[Vessbot]

This isn't 737-specific (never flown the type) but if it's an EFIS one with an AOA-based stall cue on the airspeed tape, it's a perfect time to use it for live info in a dynamic situation where everything that matters is changing: airspeed, stall speed, elevator authority, actual G, and stall G.

[Pin Head]

Forget the wings level bit first.


Disconnect ap
Disconnect at
Pitch down to -5 degrees
Trim
Full thrust
Roll wings level
Check soeedbrake lever down.

Wait for vref 30 plus 100 then recover

[ZeBedie]

the initial action is to level the wings and lower the nose

This from a highly experienced training captain? Gosh.

[vilas]

Airbus also recommends pinhead method.

[Dan_Brown]

Pin Head

Correct. Anyone who has been through basic flying training would know this.

First, unstall the wings!! This of course is done by unloading the wings, by lowering the nose, not leveling the wings!! Ailerons central until the a/c is under control. A jet is a fixed wing aircraft. No different to a Cessna 150, for E.G.

Don't get away from the basics. AF 447 confirmed that.

To be fair, no one has deep stalled a A340 and recovered, to my limited knowledge.

[Centaurus]

This from a highly experienced training captain? Gosh.]

From the QRH:
Hold control column firmly.
Disconnect AP and AT.
Smoothly apply nose down elevator to reduce the angle of attack until buffet or stick shaker stops.
Nose down stabilizer trim may be needed. (See warning note re excessive use of pitch trim).
Continue recovery (See note)
Roll in the shortest direction to wings level if needed (see warning Note)
Advance thrust levers as needed.
Retract the speed brakes.

The critics have a point. Just testing you:E The order should be lower the nose while actioning all the other parameters asap.

[olster]

This is the danger of pprune. Follow QRH / FCTM guidance. It is NOT full thrust initially due 737 thrust pitch characteristics and potential for secondary stall. Also swept wing jet aircraft have very different stall characteristics to a Cessna 150 exacerbated by high altitude / mach effect. AF447 changed the stall recovery philosophy and it is key that light aircraft and swept wing jets are different aerodynamically.

[misd-agin]

Pitch down as necessary. Don’t be an numbers guy and pitch to X, pitch to what is needed.

Recovery? Read the language - 0.3G protection .... that is the lightest of back pressure. How many guys only pull at 0.3G at the minimum recovery speed? Very few, which is when the secondary stall, now an accelerated stall, occurs.

[RHS]

Never heard -5 degrees before, only pitch to unstall the wing. Depending on how deeply the stall was developed that could be a very significant nose down attitude.

I’m sure someone will correct me but I have heard the A350 in one of its stall tests required almost 30 degrees nose down pitch to recover, in part due to some CofG issues, but still shows the point!

[olster]

At high altitude, with mach effect and less dense air coupled with swept wing aerodynamics the pitch attitude to unstall the wing is markedly below the horizon and will result in a considerable loss of height. This is one of the conclusions of the AF447 catastrophe, the fact that a stall condition was not recognised by an apparently well trained crew. The traditional 'cessna' style recoveries with minimum height loss are not applicable to jet transports. The height loss is a factor when related to terrain proximity which is part of general SA. QRH / FCTM applies and beware tips / techniques from unverifiable sources!

[Vessbot]

Pitch down as necessary. Don’t be an numbers guy and pitch to X, pitch to what is needed.



But then how could it be taught on a slideshow and tested by a multiple choice test, what are you out of your mind?! :8

[Vessbot]

On a serious note, a big pet peeve of mine about this topic is when people call it a "high altitude, low energy" situation. It is not low energy, from 30,000 feet you have gobs of energy below you (namely, 1491 knots' worth) to use. That is, as long as you have the understanding and fortitude to use it.

Of course, I know they mean "low kinetic energy" and not "low total energy," but in that case they could have just said "low airspeed" with no loss of information. But no, they have to muddy the waters by using the fancy high tech sounding term. Unqualified "energy" is supposed to mean "total energy."

[vapilot2004]

In my high altitude stall sessions, which notably just began a little over a decade ago during recurrent training, the recovery has never been immediate, particularly when the setup included plenty of NU trim by George prior to the stall.

Centaurus is quite right regarding the underslung engine pitch considerations at altitude - the onset of thrust is far slower than when down low and the sim modeling clearly shows this.

Speaking of sim modeling, according to the experience of NG test pilots, the buffet during the approach to a high altitude stall is so pronounced, one would have to be in a coma to miss it. This is an area where the simulator lacks fidelity.

[atakacs]

I’m sure someone will correct me but I have heard the A350 in one of its stall tests required almost 30 degrees nose down pitch to recover, in part due to some CofG issues, but still shows the point!

Are all modern type high altitude stall tested? I'd really be interested in seeing the video of a 380 or 777max stalled at fl400

[sheppey]

I must admit our -800 sim gives a very significant amount of buffet. Perhaps no where near that of an aircraft but I can't imagine not noticing..

In the simulator, that is a good reason for the instructor to follow up the high level stall recovery (37,000 in the case of the 737 CL) where heavy buffet occurs well before stick shaker actuation, with a stall recovery in the landing configuration at low altitude - typically ILS - where the stick shaker occurs and no buffet at all. The contrast between the two types of stall and recovery technique (clean high altitude and landing configuration on final), is quite astounding.

Replicating the Turkish Airlines B737 Amsterdam accident where the thrust levers closed due to a defective radio altimeter while flying the ILS is also most instructive.

There, the continuous back trimming of the stabiliser as the autopilot tries to maintain the aircraft on ILS glideslope at idle thrust means when the stall recovery is attempted when the stick shaker actuates while disconnecting the autopilot, considerable forward stab trim is needed for several seconds, coupled with a delicate balancing act in terms of elevator pitch control by the pilot to prevent critical height loss during the recovery phase from VREF minus 25 knots. This is where manual flying skills are absolutely vital; especially if the event happens in IMC or night.

[sheppey]

Speaking of sim modeling, according to the experience of NG test pilots, the buffet during the approach to a high altitude stall is so pronounced, one would have to be in a coma to miss it. This is an area where the simulator lacks fidelity

I agree with the NG test pilots comments. I don't think all simulators lack the fidelity. Certainly the buffet is very heavy in the 737 Classic simulator I am familiar with. Maybe it depends on the fidelity (serviceability) of each particular simulator?

[Pin Head]

Low level recovery I target 5degrees NU with a mid thrust settings.

As mentioned target the pitch attitude, hold then possibly like Turkish, lots and lots of trim.

[Dan_Brown]

What about deep stall recovery? I ask, as if the initial stall recovery is not completed correctly and a secondary stall developes and then a deep stall. I.E., stabiliser also stalled. You need to regonise and recover from that very quickly, as the RofD increases at an alarming rate.

In any fixed wing aircraft, the wings must be unstalled whether it be a C150 or an A380. Apply all the power or trim you like. You are going nowhere, except down unless those wings begin to produce sufficent lift.

[vilas]

Simulators are programmed to behave according to the data package which is given by the manufacturer based on test flight results and wind tunnel data. The buffet will not happen unless it is programmed. The device limitation may produce less but not more. Also about deep stall etc. Simulator behaviour is not authentic in the region outside the envelope where test pilot hasn't gone and no data is provided. So such exercises are misrepresentative of actual aircraft behaviour which no one knows.

[Dan_Brown]

Exactly!

Why havent they carried out these tests? Surely if the deep stall tests could be carried out during test. If the situation was unrecoverable, then a recovery parachute in the tail could be deployed. That should at least get the nose pointing down. I thought test pilots were of the "right stuff". Seems i maybe wrong. Are crews now, part of the test flight program? Has Health and Safety hamstrung flight testing also?

Yes i know we shouldnt get into these situations but we do, humans being humans.

[safetypee]

Dan, most manufacturers explore both the stall boundaries and after effects.
Depending on aircraft type, stall characteristics can vary widely. Small differences in build quality or maintenance, structural flexing, weight variation, control rigging, ... all add variability to many uncalculable aerodynamics effects.

See the NASA report relating to 737 stalling, including high altitude. There is reference to a simple stall model suitable for the task, but first define the task; awareness, recognition, avoidance, or recovery. Then provide the funding according to means and need, considering the ever present variability of the human. You could train everyone, but never be assured of the behaviour in operation.
And how many accidents have their been from unrecovered stall encounters in situations where recovery was feasible, i.e. not very low altitude, impaired controls, etc.

“All airline pilots agreed or strongly agreed that they were surprised by the surprise stall scenario. In that scenario, less than one quarter of the airline pilots strictly followed the proper stall recovery procedure on which they had been briefed. Less than half maintained a nose-down input until the stall warning stopped.
It may not matter what stall model you use if pilots are going to react inappropriately; better to avoid the situation altogether.

https://www.faa.gov/pilots/training/media/Evaluation_of_Stall_Models_for_Training.pdf

[mustangsally]

This thread has gone from a simple discussion to the absurd! Deep stall discussion is similar to how low can you go. Simulators are toys programed to behave and react in certain ways that are predetermined. Stall should be recovered from with the least amount of altitude lost even if the buffet continues for several seconds longer. A buffet can occur at cruise when operating at almost maximum altitude and a bank of something around 20 degrees. Apply some thrust and minimum roll and the buffet is gone. I remember the days of training in light aircraft. Idle thrust hold altitude and wait of the buffet/horn. Keep the nose up and wings level in falls through. Don't change a thing, the nose falls, speed rebuild followed by another stall, again and again.

The discussion about don't roll wings level is really more airframe specific. Some use a spoilers for roll, that brings about a whole new topic.

Keep it simple and you will not kill yourself.

[Vessbot]

Stall should be recovered from with the least amount of altitude lost even if the buffet continues for several seconds longer.
Why?


The discussion about don't roll wings level is really more airframe specific. Some use a spoilers for roll, that brings about a whole new topic.


Spoilers or no, if the region of the wing where the aileron is is stalled, an aileron input will stall it deeper and the plane will roll counter to the roll input.

If there's no need for a hurry to roll, better to wait longer rather than shorter to make sure the wing is completely unstalled.

[wiggy]

Vessbot...agreed..I thought for good reason powering out of stalls had gone out of fashion, certainly on anything with underslung engines....

I certainly can’t speak for the 737 but FWIW after the well known high profile stalling/ incidents/accidents worldwide a few years back our Boeing big twin procedure was amended by Boeing to this:

Initiate the recovery:
Smoothly apply nose down elevator to reduce the angle of attack until buffet or stick shaker stops
....
Continue the recovery:
Roll in the shortest direction to wings level if needed*
Advance thrust levers as needed.....

(My emphasis added)

As currently taught (and as in the QRH and FCTM) the emphasis is on doing it very much sequentially i.e. you must get rid of the buffet before rolling or applying thrust.....

[fulminn]

Forget the wings level bit first.


Disconnect ap
Disconnect at
Pitch down to -5 degrees
Trim
Full thrust
Roll wings level
Check soeedbrake lever down.

Wait for vref 30 plus 100 then recover

5 deg down, full power and waiting for 250 kcas...yes then i ll look for you at the center of the earth...ffs

[misd-agin]

Some really bad information here. 5 dog nose down might not break the stall. And waiting for x airspeed to pull?How hard are you going to pull? How heavy are you? How high are you? Or does any of that aerodynamics and physics stuff matter?

Simulators don’t have post stall AOA fidelity. That’s the change. A and B have agreed to a generic n/b post stall fidelity model.

You can’t compare current, or especially older, ‘stalls’ in a simulator and pretend they’re the real thing. They’re not.

I’m not sure how you can look at this video and write “apparently well trained” -
https://m.youtube.com/watch?v=0a06A78iXnQ

[safetypee]

Attempting to answer Centaurs’s opening question logically;
Emergency manoeuvres - EGPWS Pull Up, Windshear - recommend speeds as low as ‘respecting the stall warning speed’, normally 1.1 stall speed.
However, this assumes that the aircraft has a stall warning system which corresponds with the general certification requirements - surprising if not. Furthermore, that the high level stalling characteristics are similarly warned, and that the stall margin (Mach effects) enable reasonably safe flight at this low speed - possibly not.

Given that altitude loss is not an issue at high altitude - no not even considering risk of collision etc, etc; focus on the primary safety issue. Then starting a gentle pull up after loss of stick shake, aiming to level / climb at a higher speed (min manoeuvring?) would appear to be safe. But further problems are the sensitivity of the speed display at altitude (flap speeds, etc, not available) and the use of Mach for reference. These similarly can be overcome by trading altitude for speed - turb speed, which might be required anyway for turbulence/ manoeuvre, i.e. addressing factors which could have contributed to the stall situation

Always test assumptions and logic - comments?

[Check Airman]

Stall should be recovered from with the least amount of altitude lost even if the buffet continues for several seconds longer.

That is exactly what you should NOT do. That technique works fine during an approach to a stall, but will quite likely get you killed in an actual stall. 747 or C150

[vilas]

Why havent they carried out these tests? Can the commercial aircraft be tested like an aerobatic aeroplane? The design and purpose is to fly them within certain boundaries. If for whatever reason a line pilot ventures beyond that then the uncertainty of the outcome must be accepted. China airline 747 survived a barol roll but wasn't designed or can't be tested for that.

[Loose rivets]

Super trio of Tube's by D Davis' days test flying. I thought I'd pop in for a moment, but two hours later I was still hanging on every word.

I'd owned his book since 1970, though seen my crew's later copies, however, I'd never heard him speak before. A bit of Winkle Brown in his delivery.

One thing in the later book was an impassioned plea to enable crews to be able to get hands on a real aircraft for occasional real flying. Probably gave bean-counters nightmares.

I was lucky, for years I was able to take the real aircraft into the stall, (Viscount) or push, (BAC 1-11) It's true to say that while I enjoyed that era, I was always rather perplexed by the lack of trainer's knowledge about pulling out of the (substantial) dive. I recall doing two or three in quick succession from 30,000 and getting a good view of the ocean before feeling any significant g. I had NO guidance on the recovery commencement. Great fun.

Of course, getting the load off the wings was done for me by the nitrogen ram. The Claxton made quite sure one was not nodding off.

[Bergerie1]

If you want to hear what D P Davies had to say about stall testing and other aspects of certificating aircraft, go to this thread. These are the ones I think Loose rivets was referring to above.

https://www.pprune.org/tech-log/602953-d-p-davies-interviews-certificating-aircraft.html

[megan]

Why havent they carried out these tests?A couple of DC-10's have been accidentally stalled with the result that various bits fell off due to the buffeting.

Report: Fedex DC10 near Raymond on Jun 14th 2008, aerodynamic stall while in holding (http://avherald.com/h?article=429149bb&opt=0)

http://www.fss.aero/accident-reports/dvdfiles/US/1979-11-11-US.pdf

[piratepete]

Vesspot. WHY? Because you might be near the ground and die.Stupid statement.

[piratepete]

Check Airman.Because you might be near the ground and die! Again a stupid statement from you.

[piratepete]

At high altitude its not important how much altitude you lose but hear the ground YOU MIGHT CRASH BURN DIE

[ZFT]

[QUOTE=misd-agin;10055151]Some really bad information here. 5 dog nose down might not break the stall. And waiting for x airspeed to pull?How hard are you going to pull? How heavy are you? How high are you? Or does any of that aerodynamics and physics stuff matter?

Simulators don’t have post stall AOA fidelity. That’s the change. A and B have agreed to a generic n/b post stall fidelity model.

You can’t compare current, or especially older, ‘stalls’ in a simulator and pretend they’re the real thing. They’re not.

/QUOTE]

I’m not sure I understand what you are stating here.0

As of now (most) regulations only require datapacks with stall models up to onset of initial buffet or thereabouts.

On March 30, 2016, the FAA published changes to the 14 CFR Part 60 Qualification Performance Standards (QPS) that define updated general, subjective, and objective testing requirements for high angle of attack modeling and the qualification of full stall maneuvers on Level C and Level D FSTDs.

EASA published NPA 2017-13 addressing many changes including advance stall.

Some of the founding members of AUPTRA have conveniently merged UPRT with advanced stall to produce ridiculously high cost aero model add ons for FSTDs

Most changes will be in regulations from 2019?

[Dan_Brown]

Can the commercial aircraft be tested like an aerobatic aeroplane? The design and purpose is to fly them within certain boundaries. If for whatever reason a line pilot ventures beyond that then the uncertainty of the outcome must be accepted. China airline 747 survived a barrel roll but wasn't designed or can't be tested for that.

Problem was AF447 was stalled and remained stalled until it hit the water. However the crew did not appear to have recognised they were in the stall. If they had known the situation, they would have attempted the correct recovery procedure. They didn't lower the nose sufficiently, IMHO. In the latter stages, was the situation recoverable? See FD recovered. I think they would have known if they were in a barrel roll, don't you??

[vilas]

The point is test flights are done to meet certification requirements. Also commercial aircraft cannot be built like combat aircraft. Then only thing they will carry is fuel. Besides since there are no ejection seats test pilots cannot risk there lives unnecessarily. It will be safer to ensure through better training that pilot will remain within the envelope. Stay clear of 447 otherwise there will be another 10000 replies.

[macdo]

Having just done an exercise in a 330 sim which was in some ways to replicate the AF447 incident, the amount of pitch down and altitude loss to unstall the wing, and then recover without inducing a secondary stall, was quite memorable. A few hands worth of forward trim helped.

[Check Airman]

Check Airman.Because you might be near the ground and die! Again a stupid statement from you.

Almost exactly 9 years ago (February 12, 2009), 50 people died, in part because a crew attempted the technique you're advocating.

I don't know if you're unfamiliar because you're too new to flying to know of this accident (in which case shame on your instructors), or you're unfamiliar because you stopped flying prior to that.

In either case, the industry has moved on, and we no longer teach people at any stage (private through ATP) to attempt to minimize altitude loss. As an instructor, any student I saw doing that would be sent for re-training.

[binzer]

Vesspot. WHY? Because you might be near the ground and die.Stupid statement.

Oh dear piratepete didn't read the thread title:ugh:

[vilas]

The reason for change in stall recovery procedure was that the earlier procedure was based on recovery from approach to stall. When a few crashes happened in the US because when the pilots opened thrust the pitch up prevented them from lowering the attitude. So a SAFO was issued and FAA asked the manufacturers to have relook at the procedure. There are some Airbus discussions and conferences which give good understanding of this current procedure. In that one of the test pilot explains it is difficult even for them to identify between approach to stall and real stall. When the emphasis was shifted from preventing loss of height to reducing angle of attack many airlines were uncomfortable and asked what about low altitude stall? So the obvious answer was same procedure. One thing has to be understood that one cannot afford to stall near ground and if you have been that sloppy then some loss of height is inevitable in recovery. You definitely have to reduce the AOA but how soon to recover the flight path will depend on the how close to ground one is and even then if you begin too early it will stall again. The commuter crash was stall near ground. The thrust didn't help, may be they would have still crashed if they would have lowered the nose. In the air every situation is not recoverable. The only way to ensure safety is not to get into those situations.

[mnttech]

On 5/31/16 the FAA's NSP released FSTD #2 which addresses "Full Stall, UPRT, Icing, Crosswind, and Bounced Landing Training Tasks"
https://www.faa.gov/about/initiatives/nsp/fstd_dir/media/FSTD_Directive-2.pdf
Which adds 7 new areas the airframe/simulator MFG must address:
3. After March 12, 2019, any FSTD being used to obtain credit for full stall training maneuvers in an FAA approved training program must be evaluated and issued additional qualification in accordance with this Directive and the following sections of Appendix A of this Part:
a. Table A1A, General Requirements, Section 2.m. (High Angle of Attack Modeling)
b. Table A1A, General Requirements, Section 3.f. (Stick Pusher System) [where applicable]
c. Table A2A, Objective Testing Requirements, Test 2.a.10 (Stick Pusher Force Calibration)[where applicable]
d. Table A2A, Objective Testing Requirements, Test 2.c.8.a (Stall Characteristics)
e. Table A2A, Objective Testing Requirements, Test 3.f.5 (Characteristic Motion Vibrations – Stall Buffet) [See paragraph 4 of this section for applicability on previously qualified FSTDs]
f. Table A3A, Functions and Subjective Testing Requirements, Test 5.b.1.b. (High Angle of Attack Maneuvers)
g. Attachment 7, Additional Simulator Qualification Requirements for Stall, Upset Prevention and Recovery, and Engine and Airframe Icing Training Tasks (High Angle of Attack Model Evaluation)

This has been an item of interest of the NSP before AF, since before 2009 I have had NSP inspectors ask to take the simulator to 35K and do some stalls. The point I'm hopefully making is that unless the FAA approved simulator has high altitude stalls listed in the SOQ (which should be available to you) the modeling may or maynot be correct.

[misd-agin]

Having just done an exercise in a 330 sim which was in some ways to replicate the AF447 incident, the amount of pitch down and altitude loss to unstall the wing, and then recover without inducing a secondary stall, was quite memorable. A few hands worth of forward trim helped.

Makes the posts about pitching down “5 degrees” seem naive or very mis-informed, doesn't it?

[misd-agin]

ZFT - we are in agreement -

[QUOTE=misd-agin;10055151]Some really bad information here. 5 dog nose down might not break the stall. And waiting for x airspeed to pull?How hard are you going to pull? How heavy are you? How high are you? Or does any of that aerodynamics and physics stuff matter?

Simulators don’t have post stall AOA fidelity. That’s the change. A and B have agreed to a generic n/b post stall fidelity model.

You can’t compare current, or especially older, ‘stalls’ in a simulator and pretend they’re the real thing. They’re not.

/QUOTE]

I’m not sure I understand what you are stating here.0

As of now (most) regulations only require datapacks with stall models up to onset of initial buffet or thereabouts.

On March 30, 2016, the FAA published changes to the 14 CFR Part 60 Qualification Performance Standards (QPS) that define updated general, subjective, and objective testing requirements for high angle of attack modeling and the qualification of full stall maneuvers on Level C and Level D FSTDs.

EASA published NPA 2017-13 addressing many changes including advance stall.

Some of the founding members of AUPTRA have conveniently merged UPRT with advanced stall to produce ridiculously high cost aero model add ons for FSTDs

Most changes will be in regulations from 2019?

[Loose rivets]

I've mentioned it before but James Hamilton-Patterson's Empire of the Clouds is a superb read. I've also laid hands on the bigger copy with lovely colour pictures. James, who was kind enough to review the flying in a storm chapter of my novel, really conveys with passion the era that D Davis gave the talks on. Somewhere, he made an extraordinary statement. It followed the D110 crash at Farnborough.

Words to the effect, Back then there was not the litigious society we have today. If a tragedy happened we were expected to just pick up the pieces of our lives and get on with it.

I suppose years of war made us more pragmatic . . . for a while.

[galaxy flyer]

Makes the posts about pitching down “5 degrees” seem naive or very mis-informed, doesn't it?

I’m guessing on the order of 30* down pitch?

[Vessbot]

Saying a big number is as naive as saying a small number. It depends on how deep the stall is, how long before recovery is initiated, how much thrust there is, how much elevator authority there is...

I'm an American and I learned the expression "how long is a piece of string" from this forum, and it seems to perfectly apply here.

[galaxy flyer]

I was referring to the post above on A330/AF 447 recovery, specifically.

[macdo]

I’m guessing on the order of 30* down pitch?
Around 25, from a well developed stall, and for what seemed like ages until you could apply pitch up successfully. The Youtube video posted earlier was very similar. Add night, turbulence and IMC to make a genuine horror story.

[john_tullamarine]

A few thoughts ..

(a) a lot of the problem derives from older operational approaches to stall recovery. In general, the operational concern was stall near the ground (typically the usual stall turning final trick) where ground contact was a major concern.

(b) unfortunately, the operational folks evidently didn't make a practice of reading what the certification folks had to say and a disjoint arose.

It is useful to have a read of the flight test guide procedures

For heavies (https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentID/1020494)

For lighties (https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentID/1019676)

(c) likewise it is useful to read what the test folk have to say on the subject .. plenty of threads in PPRuNe, eg Evaluating stall characteristics - best procedure? (https://www.pprune.org/flight-testing/392357-evaluating-stall-characteristics-best-procedure.html?highlight=stall+recovery). In the present thread, one would do well to heed Safetypee's counsel .. he, amongst others in the certification side of the PPRuNe community, has a lot of runs on the board from which to draw when it comes to suggesting this and that.

(d) as has been observed, AF 447 was a bit of an Industry wake up call in respect to stall recovery and led to considerable training changes. This doesn't, necessarily, mean that height loss can be ignored .. but let's keep the concerns appropriate to the inflight circumstances. At day's end, the aim is not to die and one should be playing the risk cards in the best manner to achieve that desirable end goal.

(e) as to what target body angle might be appropriate, that remains a bit hit and miss in the absence of an angle of attack indication, or some other means of deducing that information from what is provided.

[misd-agin]

“How much bank do you think you’ll get if you stall it at altitude?” - guy in the know.

Since he’s asking it must be something significant - “IDK.”

“How about 60-70, to both sides.”

Five degrees nose down wouldn’t have been enough.

[misd-agin]

(e) as to what target body angle might be appropriate, that remains a bit hit and miss in the absence of an angle of attack indication, or some other means of deducing that information from what is provided.


Which is why the whole ‘target pitch attitude of X’ is nonsense. TRI has decided -10 worked. Airplane had an AOA readout. So I pushed the nose ever lower using the AOA - “no. Use -10.” The slightest back pressure, perhaps still less than 1 G, triggered a stick shaker. “I don’t know what happened but it should work.”

New TRI in the fleet, no AOA experience, had come up with his own ‘technique.’ Debrief, and immediate call to fleet manager, knocked that nonsense off.

[galaxy flyer]

Around 25, from a well developed stall, and for what seemed like ages until you could apply pitch up successfully. The Youtube video posted earlier was very similar. Add night, turbulence and IMC to make a genuine horror story.

That was my experience in running fighters out of airspeed in the vertical; once it pitches over like plumb bob, it takes awhile to get useful energy to bring the nose up. The high level stall profile in the Global was done in the 40s; same deal long wait with the nose down until reaching about M.74-ish. But that was more like an approach to stall, not fully developed.

You need what’s required to “break” the stall and see the plane start accelerating. AoA indications are very hrlpful here.

[piratepete]

Check Airman.
I really hope you are not a check airman.I am (TRE version for 28 years).The UK CAA was so concerned about this is issue they sent out a SAFETY NOTICE on it a few years back.
If you have no ground contact issue then altitude loss is not the primary concern.If ground contact is a factor then WATCH OUT.You must balance the need for unstalling the wing against hitting the ground.How can you argue against this? Silly and very dangerous.

[Vessbot]

You should check again the comments he was replying to: a pair of unnuanced parrotings of the old dogma solely concerned with altitude loss. If there's any "balance" to be had, he was shifting the discussion toward its proper place (especially in a thread explicitly about high altitude stalls).

Plus, if you don't unstall the wing you're guaranteed to hit the ground. If you do unstall it, you stand a chance of pulling out. At what point does the balance fall in favor of not unstalling the wing? And how many recent accidents have been caused by too aggressive unstall vs. failure to unstall?

[vilas]

Pirate pete
You must balance the need for unstalling the wing against hitting the ground.How can you argue against this? Silly and very dangerous. The need for unstalling is paramount because that's what is causing loss of control. Perhaps what you meant was need for early recovery of flight path after unstalling against hitting ground. That's quite another thing. Unstalling the wing is the first action of eventual flight path recovery, may be sooner or later. But as I have said earlier if you are guilty of full stall near the ground there are no guarantees. In India in early days of the MIG21, the phenomenon of superstalling of delta wing wasn't understood correctly where once the AOA went past the critical the drag rise was huge. You needed to put the nose down to unstall because power won't do it. With ground rushing up it needed courage to do that and there have been cases when it wasn't done the aircraft has crashed with full after burner on

[piratepete]

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.

It is extremely important for all instructors to point this out and give demonstration.Many TRIs emphasize that minimum altitude loss is the key to a "correct" recovery.This is true near the ground but is not the sole measure of correct technique.

[Check Airman]

https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_120-109A.pdf

From page 7 of AC 120-109A (my bold)

Additionally, recovery profiles that emphasize zero or minimal altitude loss and the immediate advancement of maximum thrust have been eliminated. Recovery procedures now emphasize:
• Disconnecting the autopilot and autothrottle/autothrust systems,
• Reducing the airplane’s AOA immediately,
• Controlling roll after reducing the airplane AOA,
• Managing thrust appropriately, and
• Returning the airplane to the desired flight path.

[binzer]

Piratepete. Read the thread title if you want to talk about low alt stalls start a new thread. You are calling people's comment stupid. I think you are making yourself look that way. :ugh:

[piratepete]

Binzer.Agreed.But in 28 years of simulator training I have seen various TRIs and trainees only apply one type of recovery.Unlike Trump, I CAN read.However it is very important to consider the WHOLE issue not just one aspect.Perhaps im stupid but im still a TRE and treat this issue with great care.Too much emphasis on one method only has a lot of risk attached.Sometimes powering out is the better method, of course at altitude primarily unstalling the wing is correct technique.Have an open mind Sir.

[Check Airman]

Sometimes powering out is the better method, of course at altitude primarily unstalling the wing is correct technique.

1. AF447 was unable to power out of the situation. CJC3407 was also unable to power out of the situation.

2. We'll agree that at altitude, unstalling the wing is primary. What's the primary concern in a stall at low altitude?

[vilas]

piratepete
But in 28 years of simulator training I have seen various TRIs and trainees only apply one type of recovery. Unlike Trump, I CAN read. However it is very important to consider the WHOLE issue not just one aspect. Perhaps im stupid but im still a TRE and treat this issue with great care. Too much emphasis on one method only has a lot of risk attached. Sometimes powering out is the better method, of course at altitude primarily unstalling the wing is correct technique. Have an open mind Sir.
I hope you read my post 44 and 59. Out of the 28 years at least twenty years powering out of stall was taught. Only now the procedure is changed. The new procedure asks you to unstall irrespective of altitude. Your concern of ground contact at lower altitude is correct but for recovery from stall it is not the altitude but whether the aircraft has stalled or is on the verge of stall with stall warning is important. If the aircraft has stalled you cannot power out of it. Stall warning is not stall. To give you airbus figures stall warning is set at alpha max+4 degrees and stall occurs even later. It will depend on rate of change of AOA also. So if you are on the verge you may succeed in powering out of it because you haven't lost control yet but if you are in full stall it will not work. It cannot be taught as an alternate method. Yes! after unstalling you may have to begin recovery of flight path sooner.

[galaxy flyer]

Pirate Pete,

Are we talking about a stall or an “approach to stall” where buffet begins, IAS numbers go red, etc? Big difference.

[Goldenrivett]

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%20Briefings%20_%20Presentations/Flight%20Ops%20-%20Stall%20recovery%20Presentation%20Airbus%20June%202010.pd f

"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."

[Vessbot]

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.

[Avenger]

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 (http://www.boeing.com/commercial/aeromagazine/aero_03/textonly/fo01txt.html)

[RAT 5]

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.

[Vessbot]

"Aerodynamic Principles of Large-Airplane Upsets"

[piratepete]

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.

[piratepete]

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.

[Check Airman]

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.

[italia458]

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.

[RAT 5]

There are also times when pilots have to that rare of tasks calling piloting.

https://youtu.be/VqmrRFeYzBI

But I do wish ATC would have shut up.

[vilas]

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.

[misd-agin]

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.

[misd-agin]

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.

[RAT 5]

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>

https://youtu.be/IKPsV9deZzI

[Stuart Sutcliffe]

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.

[PEI_3721]

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/2009/20090225-0_B738_TC-JGE.pdf

[italia458]

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.

[RAT 5]

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.

https://youtu.be/JVZUGu49XlE

[Centaurus]

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:ok:

[PEI_3721]

Cent #85, flap 40-15.
This illustrates one of the problems of procedural teaching; the accident crew were in a GA mindset, whereas due to the RA/AT malfunction recovery from an approach to the stall was required.

With the continuing focus on procedures, situations may be considered the same without checking for differences or need to adapt.
Thus expecting a stall recovery procedure to be the same at high altitude and low altitude might not be correct. Unstalling the wing by reducing the AoA would be consistent, but the subsequent recovery might vary with altitude, weight, configuration, etc. Crews have to be prepared to reassess stressful situations and modify procedures accordingly.

I suspect that the absence of detail in the Boeing procedure for high level stall refects the above, where the answer is ‘it all depends’. Unfortunately there is less understanding or ability to judge what ‘it’ is.

Re my #82, lest anyone thinks that they can recover from a stall at low altitude within 800ft, then reconsider terrain profiles and obstacle clearance.
The safety lesson is to focus training on how to avoid an approach to the stall particularly in the descent and approach phases of flight, and not low altitude stall recovery. This training would provide greater consistency and avoid the need for surprising situation assessment and emergency procedure recall.

[fdr]

Clean at altitude, the B737 has a gentle stall behaviour, easily within FAR25.203 criteria. Adding power is as noted almost irrelevant at high altitude. The most notable characteristic is a low frequency moderate vertical acceleration at the flight station, from aerodynamic buffet on the tail.

At low to mid altitudes, the effect of thrust is more significant, and will reduce nose down elevator authority for a fixed trim condition. At the low to mid altitudes, if conducted dirty, the stall buffet is pronounced, with moderate to heavy vertical acceleration felt at the flight deck. The aircraft meets 25.203 again, but you can expect reasonably sharp rolloff if the stall is accelerated. Any mis rigging of the slats will result in a rolloff with autoslat extension as well.

The stalls at low to high altitude, clean through to landing configuration are obvious with good control response available, with the caveat that thrust couple can compromise the fixed trim pitch authority. While the B737 has a speed trim system, with it working, the stick force per g remains positive through the flight regime.

Any test or flight resulting in aerodynamic stall requires an inspection per the AMM, which is heavy on the empennage, for good reasons. The buffet is pronounced. Having investigated other types that have had deep buffet boundary excursions, resulting in flow conditions that have literally torn carbon fibre outer elevators in half, buffet events should be taken seriously with post flight inspections.

Mach buffet on the B737 is different to the stall buffet, but is probably not going to be recognised as such without cross check of the instruments. The onset on a B737 at 1.0G is very gentle, and increases amplitude as speed increases. The frequency of Mach buffet is higher than the stall buffet. In both cases, any unloading of the aircraft will reduce the buffet amplitude.

The most recent changes to the FCOM for all Boeing and Airbus aircraft are rational, and reflect the necessity to ensuring the AOA is reduced. The discussion on roll, rudder etc continues to approach areas of structural integrity concerns. The use of bank might well be applicable when you are flying a Folland Gnat with a jammed full aircraft nose up stabilator, but otherwise, it doesn't take much bank to get the nose coming down in the real world. Sim training ends up with examples of extreme flight angles being exhibited which will be pretty interesting in a dark night, when the reason for the upset is possibly due to instrument failure or vertigo etc. Goldilocks rule.

Unless you have ripped off tail feathers, then every aircraft known to man (other than the F101) will look after itself if the damn pilot stops mussin' with it. The aircraft will recover unless the pilot prohibits that by his actions, which we as a group have routinely done. AF429 had full back stick on for almost the entirety of its descent, there is no Cessna, Pitts, Cub, Boeing or Airbus that will survive that level of mishandling. Other than the aforementioned 101, even T tails will recover; post the magic B727 zoom climb in the eastern US from having pitot heat turned off, Boeing conducted a vigorous deep stall series and could not get the plane to "dig in", or "pitch up" (again, not so for the F101), and unless mishandled further, the plane recovered when left to its own devices.

For Airbus drivers, the control laws which are pretty neat when they are working proper like (as all computers dooooooooo.....) you are inherently set up for a pitch issue on reversion, like Perpignan, the stab trim is outside of your immediate experience of use, until the moment when you absolutely need it to control thrust pitch couple, and get the nose down so that you can collect your thoughts. The addition of the note on the ECAM of use THS trim is nice, but probably not within the cognitive capture of a dynamic upset event, where you are guaranteed to have lots of stimuli happening promptly. If THS is used, the plane is a happy camper, alternatively, if the thrust coupling is not disturbed, the plane will exhibit normal speed stability (unless you have uncommanded flight control inputs through bad sensors etc.... which is not detected as a sensor failure, almost hardly ever happens... :| ).

P.S. If you try hard enough, a B737 will autorotate... data showing that had been found in the smoking hole in the ground before today. >180 degrees a second is not impressive for a Pitts but it is pretty impressive for Ma and Pa in 35EF. AOA management will make for happier endings.

The B737 is not a bad aircraft, it wants to fly if the pilots don't mess with it too much.

In respect to AMS, going into the hover, OGE in any jet aircraft, with insufficient altitude to recover is going to end badly. The failure of the LH LRRA ws insidious, as the immediate result was not apparent to the PF and certainly the PM and the other people not looking at the energy state of the aircraft. The more emphasis management has on the flight crew acting as observers and monitors of the system, the more frequent the failure mode of out of the loop control will occur. Humans are poor at monitoring systems, that is the thing that computers do well. Humans are capable of identifying patterns that are otherwise unprogrammed, but not always. The slam dunk approach that was flown at AMS places the aircraft and crew in a position that care is needed to ensure that the performance of the aircraft as a system is monitored effectively, the systems need to act correctly and in a timely manner to achieve the outcome. In the end, the failure of the ATS to maintain a target airspeed as it had already gone to idle for the landing was not identified, and the energy loss on pitching to the glideslope and the associated speed bleed was not recognised. It was a high workload event, and the crew were unable to deal with the cognitive demand on the day, and stuff happened. Expectancy of the system behaviour being nominal becomes a reinforced trait of our flight crew due to the overall success that occurs on almost all occasions, except when it doesn't. Healthy skepticism is hard to maintain for a complete career.

[piratepete]

FDR.I thought you died long ago.Anyhow, thats a superb post, excellent, love it.

[fdr]

still alive, out of the test world and back having some fun at low level in a jet. Birds get big quick down there.

[A37575]

The safety lesson is to focus training on how to avoid an approach to the stall particularly in the descent and approach phases of flight, and not low altitude stall recovery

PEI. That is certainly one point of view, although it has one small problem.
It is akin to saying I will not teach you how to swim because that is too dangerous. Instead I will teach you how not to go near the water.:sad:

Or put another way. I will not teach you how to defend yourself against a bad guy but will teach you which pubs to avoid.. Get the drift?

[PEI_3721]

A37575, all adrift in a choppy sea.
Life and flying are uncertain; there are no absolutes, but the more the industry seeks absolutes ( SOPs, or inappropriately focussed training), then the greater the need for understanding and judgement of ‘it’ - the unexpected, surprise; - more management thought, planning, and refocussed training.

As much as pilots need to know which parts of town to stay out of (and how to judge that), so too the mechanics of stalling, because no situation (or town) will be identical. ;

FDR #87,
101 experience at PAX, or real experience north of the border ? There is lot more common sense up there.

[Jet Jockey A4]

misd-agin

This is the first time I see this montage/video of the stall/accident although I have read the reports in the past and coming away with my head shaking on how the pilots managed to crash an aircraft that was basically functional.

This video reinforces what I thought and I have to agree with you that their training was definitely sub-par but it also points to that their basic flying skills were non existent.

[EMIT]

IF power is the way out of a stall ..... how the hell then do gliders ever recover from a stall ... ?

[vilas]

G-THOF Bournemouth. They had dropped speed on approach but not stalled, decided to GA and TOGA stalled the aircraft had problem lowering the nose.

[Centaurus]

TOGA didn't stall that aircraft. Poor airmanship by the PF did. He had a problem lowering the nose as you say. That was only because he was too slow to respond to the normal expected pitch up when thrust was applied and then exacerbated the problem by failing to apply sufficient forward stab trim quickly enough to gain more elevator effectiveness; thus permitting the aircraft to pitch up beyond a reasonable climb attitude.

[vilas]

Speed below VLS on approach especially at lower altitude is poor airmanship anyway. But here it worked in reverse. He didn't power out of stall but selected TOGA for GA but the effect was same. Even in unstalled condition at lower speed if pitch up cannot be controlled how can anyone power out of stall?

[RAT 5]

IMHO full TOGA for a all engine GA is asking for trouble. I wonder what the teaching is at various operators. There are some who advocate the use of similar thrust, 85-90%-ish, that auto single TOGA gives. In manual flight, if not trained, or if SOP stipulates, PF firewalls thrust and all hell breaks lose. Controllable into nearly uncontrollable PDQ. It happened at Narita in an Airbus, but that included a mode & trim issue as well, if I remember. See my video of the Tarom airbus at Paris. In the documentary, I'll add that link, it said that the a/c responded as designed. I'm not sure if this was an inadvertent selection of GA with odd thrust & trim settings; I'm not an AB man. But it is scary of that & the Narita incidents had some startling but correct a/c reactions.
BOH was pure pilot induced.

And we still wait the report of the Russian? B737 stall crash on GA in Poland? It was their 2nd approach and they made a GA from above MDA and seemed to have pilot induced trim issues combined with thrust couple etc.

https://youtu.be/JlMdMTy8JLg

My previous #76 showed a digital reconstruction, but this clip was part of a more complete documentary into a/c confusing pilots; as you hear in the narrative. I do not know the build up to the incident, but damned glad these pilots knew how to stop digging and climb out of the hole.

[phylosocopter]

Ok probably dumb question from SLF, supposing you do get into high altitude stall due to no idea what airspeed you have, so you revert to attitude (ie put nose down) and appropriate power. Now what is the likelyhood that you overspeed and aerodynamic breakup from that position?, how would you know without airspeed info.... just asking, seems like diving from high altitude might be both necessary and fraught.

[Check Airman]

If the airspeed information is lost, we'd fly an appropriate pitch and power combination that will keep the plane safe until we can recover reliable airspeed information.

[phylosocopter]

Thank you check airman, I have managed to absorb "fly attitude and power" but that was not my question what if the craft is already in high altitude stall? in diving out of that stall how significant is the risk of overspeed and without ASI how to manage that risk?

[Check Airman]

The aircraft is tested to well beyond the published maximum speed. Faced with the choice of a potential overspeed or underspeed, I'll take my chances with the overspeed.

[Judd]

what if the craft is already in high altitude stall? in diving out of that stall how significant is the risk of overspeed and without ASI how to manage that risk?


I would have thought common sense airmanship would apply. You don't have to do a Stuka type dive to un-stall the wings. See: https://en.wikipedia.org/wiki/Junkers_Ju_87


if there is a problem with all three ASI's and you have stalled it as well, then it is not your day:sad:
In that event, keep the nose slightly below the horizon for 30 seconds and keep out of buffet then very gently level out. Not forgetting to set cruise power as part of the un-stalling procedure. Count on losing at least 3000 ft in the recovery procedure. There is probably no QRH procedure for that combination of events so you simply have to `wing it`.

[Vessbot]

. You don't have to do a Stuka type dive to un-stall the wings.

Well... sometimes you do, though. AF447 was at about 40 deg. AOA for much of its ride down. So to unstall it they'd have had to put the nose down in that vicinity. Let's say 30deg. That might as well be vertical with respect to how it would feel to a pilot only used to conventional attitudes.

[_Phoenix]

Yes, reducing the AOA is imperative and it is the only way out.
I'm still amazed that AOA indicator is not mandatory, as it should be the no. 1 instrument for the recovery of the flying wing.
The incident of Tarom at Orly is a textbook example of recovery from a hairy stall situation.
Here is the video with the actual CVR:
(click watch video on youtube, will work)
https://www.youtube.com/watch?v=VqmrRFeYzBI

[phylosocopter]

Well... sometimes you do, though. AF447 was at about 40 deg. AOA for much of its ride down. So to unstall it they'd have had to put the nose down in that vicinity. Let's say 30deg. That might as well be vertical with respect to how it would feel to a pilot only used to conventional attitudes.

yes AF447 was on my mind when i asked the question, that was a deep stall and I believe a "stuka" dive was the only option that could have saved them from that situation, as to how it would feel? well on a black night and considering falling like a stone and no ASI .... how would it feel? probably like standing still. hence my question how would you know when to pull up, perhaps "count to thirty" is the right answer after all

[Centaurus]

The incident of Tarom at Orly is a textbook example of recovery from a hairy stall situation.

The official incident report shows no evidence of "a textbook example of recovery from a hairy situation." See: https://reports.aviation-safety.net/1994/19940924_A310_YR-LCA.pdf


On the contrary, it seems clear from the subsequent investigation that, not only was the captain utterly confused about the gyrations of the aircraft caused by his own incompetence and subsequent over-controlling, but it was only sheer good fortune the aircraft did not crash. It did not help that the co-pilot was also on the controls some of the time without telling the captain. Neither had a clue what was going on following the initial strong pitch up. That was obvious from the CVR

The aircraft virtually fell into an uncontrolled steep dive of its own volition after stalling at an extreme nose high attitude. As it picked up airspeed by virtue of the steepness of its dive, the captain was able to recover by simply pulling back on the stick. There was no evidence in the report that the captain attempted to deliberately roll the aircraft to the nearest horizon in order to get the nose to drop and thus pick up airspeed for recovery.

Good luck - not skill - saved that aircraft from crashing. .

[vilas]

In that event, keep the nose slightly below the horizon for 30 seconds and keep out of buffet then very gently level out. Not forgetting to set cruise power as part of the un-stalling procedure. If you are cruising at 350 this won't help. It will need at least 4 to 5 degrees below the horizon and once the stall warning stops all the power(which is not much) you have and may be forward trim if you are in it for a while as 447 was. Since there is no speed it will be a journey from low speed buffet to shall I say high speed buffet or rumbling before you recover flight path. Very unnerving to say the least.

[RAT 5]

Centaurus: thanks for that. I had not seen the report, snd it was easy to assume the Tarom pilots were ex-military and let the a/c go with the roll and not fight etc, and thus be a hero.

Regarding stall recovery in steep dives; gentle dives and GPS ground speed can help. Stuka dives might not give an accelerating GPS GSpd. Ha.

[Centaurus]

It will need at least 4 to 5 degrees below the horizon
Vilas. Maybe it all depends on the simulator type? Having done over 50 of these manoeuvers in a Level D FFS 737 simulator, using zero body angle or maybe two degrees below the horizon at the most is sufficient to pick up to a safe recovery speed of around 235 knots depending on weight.

[vilas]

Yes! May be on aircraft type. But I think more on how long been in it. I don't think 447 would have recovered on the horizon.

[recceguy]

it was easy to assume the Tarom pilots were ex-military and let the a/c go with the roll and not fight etc, and thus be a hero.

What the hell does it mean ? I read and read again - I can only assume you are not ex-"military" (and what does it mean, "military" - fighter pilot ? transport, helicopter pilot ? Air Force, Navy, Army ? UK, Ireland, Luxemburg, North Korea ? somebody who didn't have to pay for his training, and had to go through a selection ? somebody who has University degrees you will never get close ? somebody who had to command hundred of people at war ? )

I'm one of those, and I have done dozens, even hundreds of what you call "stalls" and loss of control in aircraft raging from SEP trainers to fighters and transport aircraft - I have done barrel rolls at night in fighters, and barrel rolls with three types of transport multi-crew aircraft (only in day VFR this time, I must confess) I had my knees shaking in a couple of occasions but I'm still here, and I'm not bragging because you don't know who I am ! so I suppose I'm a hero in your minimal world ?

For those who have been through dozens of stall recoveries in a simulator not designed to replicate that, and did remain alive, I can only suggest a medal.

[_Phoenix]

Centaurus, thank you for the link, first time I see this report. In the past, I discussed about this incident with a romanian friend. He sent me the video link, with the romanian transcript, the pilot said "...oh, l-am scos!", "Oh, I took it out! (from stall), at the moment the aircraft finally pitched down. That made me believe the pilot did something good in there.

[RAT 5]

Touchy. Let's take out the hero bit, then. It seems they were not as much hands on as it was easy to assume. Sorry to have touched a nerve.

My innocent thinking, after watching the recovery profile, was that it was something not taught in a civilian UPT program. I suspect some pilots might have tried to resist the natural momentum of the a/c's pitch & roll. I too have enjoyed aerobatics in a multitude of a/c, and done what was possible in a B738 sim. Nothing like yours in the real thing.

[fdr]

TAROM was a replay of Condor with fewer wash rinse spin cycles. It was very close to CAL #1 Nagoya, and CAL #2 at CKS.

Fighting the AP becomes fun on an A300/310, and the passengers get a free disney ride. Overriding an autopilot would be nice if it led to AP disconnect, however we have seen that also end in tears in the everglades, and various other wild rides where the disconnect gets out of sorts.

Once the aircraft is out of trim with the THS and has an adverse thrust couple, the elevator authority is going to get compromised, and a wild ride often ensures. Pilot training is supposed to make up for deficient design, however that is all well and good until you get cognitive overload from a dynamic event, which the data of TAROm shows was a wild ride. Doing low level aeros is best as an observer sport, or after lots of practice in the box.

Pilots are human, any pilot encountering a compromised pitch condition at low altitude (or anywhere arguably) is going to have a pants load of adrenalin running along. Training mitigates bad design, it doesn't guarantee a positive outcome always.

TAROM like Condor, was lucky. Electrojets can get out of sort too, as USAirs A320 in Reagan, ANZ's A320 @ Perpignan did. The first one got away with it, the second one ended badly in headlines.