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AF447 wreckage found

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AF447 wreckage found

Old 27th May 2011, 20:16
  #581 (permalink)  
 
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I agree, without all the communication between the crew, and a statement that all the communications are given, what has been given may be someone's idea of a reasonable PR release: not intended to be misleading but not anticipating this depth of analysis.
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Old 27th May 2011, 20:19
  #582 (permalink)  
 
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Originally Posted by ChrisVJ View Post
...no horizon, can't trust the Altimeter, AH or ASI?
So far there are no indications that the altimeter (hence VSI) failed (they get their data from the static ports, not the pitots).
Neither are there any mentions of the attitude reference system, hence AH (or standby AH), having failed.
"No horizon ?" Normal situation during instrument flight, at night or in cloud. That's why the "artificial horizon" was invented.....
Let's not confuse the story unnecessarily.

CJ
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Old 27th May 2011, 20:22
  #583 (permalink)  
 
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The fact of the matter is that there IS NO PROCEDURE for unreliable airspeed in the cruise. I fly the 319/320/321, so I am not referring to the 330 but given that they are very similar the guessing the procedures are similar. Airbus have a procedure with how to deal with it, and if you google it you will find it. Fact is, above 10,000 ft the procedure is 5 degrees pitch with CLB power. In heavy turbulence when the aircraft is pitching allover the place then you can forget about holding 5 degrees pitch!
Not to mention the fact that 5 degrees pitch with CLB power is certainly not the best thing to do with unreliable airspeed in the cruise. Most Airbus guys now have their own pitch/power settings memorised for this - only because of AF447, and before the accident the majority of guys would have said "well, I guess its 5 degrees with CLB power as technically that is what the QRH says". All of this is not forgetting that there still is NO procedure from Airbus, the procedure in the QRH is suited to unreliable airspeed much lower down.

For those who says "why didn't the Captain take control"? Well, given the aircraft may have been out of control by that point it must have been difficult in getting to the cockpit alone, let alone getting someone who is handling the situation (badly or not) out of their seat and you strapping in. He probably decided that the two people in the seats had the best idea of what was happening as they had seen all the evidence and he had entered later on.
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Old 27th May 2011, 20:47
  #584 (permalink)  
 
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The fact of the matter is that there IS NO PROCEDURE for unreliable airspeed in the cruise.
Sorry but I think you got it wrong here...

The procedure on the 320 family says:

If the safe conduct of the flight is impacted :
-A/P and F/D off
-A/THR off
-Pitch thrust:
.Below Thrust Reduction altitude 15° Toga
.Above Thrust Reduction altitude 10° CLB.
.Above 10.000ft 5° CLB.
-Flaps Maintain.
-Speedbrake retract
-L/G up.
.When at or above MSA or circuit altitude level off for troubleshoot.

Therefore if it happens during cruise, and safe conduct of the flight is impacted you have to go for 5° and CLB, then level off, and go for the pitch power data from the checklist.

If instead the safe conduct of the flight is not impacted (which was definitely not the case for the AF) the memory items can be skipped and the pitch power data used to maintain the level.

I am not accusing the AF pilots involved of not having used the proper procedure (too little details have been released at this moment especially on the intensity of the turbulence ), I am just saying that the procedure for unreliable speed is clearly there..

Speevy
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Old 27th May 2011, 20:49
  #585 (permalink)  
 
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Fodder for us more thoughtful types:-

"The stall warning sounded twice in a row. The recorded parameters show a sharp fall from about 275 kt to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments later in the speed displayed on the integrated standby instrument system (ISIS)."
This is what I'd expected and earlier predicted here in this thread as being the "onset" (an eventual total pitot clog - see explanation at post 335 (page 17) on this thread ). The DFDR was of course recording exactly what the pilots were seeing but meanwhile the aircraft's autothrust had actually been increasing power to maintain that programmed speed (and as a result of the gradual ice-crystal pitot blockage, actually exceeding that programmed speed by a considerable margin, whilst headed towards Mach Crit). But what triggered the autopilot disconnect? Was it a Mach Crit encounter or was it that the autopilot couldn't hold the increasing elevator force gradient of a system-driven mis-set THS (hoz stabilizer)? Or was it the sudden total clog of the pitots (see hail formation "exponential" analogy at my previous post).

"At 2 h 10 min 51s, the stall warning was triggered again. The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs. The recorded angle of attack, of around 6 degrees at the triggering of the stall warning, continued to increase. The trimmable horizontal stabilizer (THS) passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight." Over time, as they cruised in the ice crystals of Cirrus cloud (a known "pitot heat capacity" anomaly for that mark of pitot tube), the gradually clogging pitot system resulted in the autothrust incrementally applying power to stop the "apparent" speed decay. Similarly, the auto-trim maintained the nose-up trim for that programmed speed - and the autopilot offset the elevator (via "fwd stick") to hold height - as the aircraft was actually flying faster than shown. When it reached its design pitch-holding limit (i.e. the max nose-down force gradient it could hold), the autopilot gave up, and the handling pilot now had an instant unalerted surprise handful of an aircraft in Direct Law with nearly full nose-up trim and near to full power. So did the DFDR faithfully record this or did the BEA just construe (and misrepresent) it as the pilot's aft sidestick input? i.e. in the absence of any better/more logical explanation?

When it comes to high speed protection, should this crew have received wrong airspeed info indicating a high speed situation, you have protection where, once Mmo + few kts has been exceeded, you will get an auto pitch-up to try and maintain Mmo + few knots, so should this happen at slow actual airspeed, it will not be too hard to see why the pilot may have continued to pull back and continue increasing the acft's pitch angle. But my theory was that they were actually at an initially higher speed than indicated. Here (most importantly) we have to consider that after their involuntary zoom climb (due trim), the static pressure changes would thereafter have had a considerable additive (and further confusing) effect upon the blocked pitot systems and the displayed airspeed/mach. i.e. ( "The speed displayed on the left side increased sharply to 215 kt (Mach 0.68). The airplane was then at an altitude of about 37,500 ft and the recorded angle of attack was around 4 degrees.")

"the angle of attack exceeded 40 degrees" later saith the report. You have to close your eyes to this, because it's not anything those AF447 pilots would have known (i.e. no AoA display for them).

"By the time it reached the apex of the ensuing pitch-up and subsequent " bunt" (around 38,000ft), the aircraft was ACTUALLY entering into a deep stall with a forward speed of around 60kts and a high angle of attack...ultimately resulting in the 10,000ft +/minute Rate of descent at high AoA. But they'd initially responded correctly to the stall warning with TOGA power? - however that response was soon to change. Why? In Direct law, which they should now have been in, holding the stick back will maintain that stall. But why would the pilot do that back-stick thing? Perhaps they were attempting to attain level flight - and unaware that they were in Direct Law? But was there another reason and why did they then idle the TOGA thrust? Who knows for sure? But here's a clue. In the subsequent descent with static pressure increasing and the pitots still blocked?, even though the airplane was actually stalled (complete with stick-shaker) the indicated airspeed would be increasing alarmingly - courtesy of increasing static pressure. That's my guess - and it's anyways a physical fact, Been there and done that trick with frozen trapped water in the static lines (i.e. the opposite effect of trapped dynamic pitot pressure). There's also a report on the Irish Accident Board's site about a 747 on a test flight with uncapped static lines due maint error. It's an elucidating gaelic tale that shows just how confusing the pitot-static scenario can be. See below for how much a 1000feet of altitude change is worth in terms of additional "displayed knots". Ask any instrument technician. That's what I did. He'll demo it for you on his test-bench.

As somebody said: "All this will probably come down to crew composition, very high workload, in adverse weather conditions, having to manually hand-fly an aircraft which suddenly found itself in alternate law at high altitude due to spurious information being fed to not only the flight display computers, but also the flight control protection and guidance computers, simultaneously." Suddenly? Don't underestimate the power of surprise. Spurious info? Maybe, but when it's what you are taught to believe (your instruments), that's what you react and respond to. You see a high and increasing airspeed and you apply backstick to attempt to control it - and you idle the throttles..... but instead you are (unbeknownst to you) embedding yourself in a deep-stall condition. Will the stall warning cease once embedded in deep-stall at 40 degs AoA?. That's my guess. That they were non-plussed by developments is obvious from the limited dialogue. Even the captain was struck dumb by what he saw. No solution was obvious in the time available - as the airspeed was seen to be much more than just "adequate" (i.e. even high - and even higher as the static pressure increased inexorably upon descent) i.e. so how could they be stalled? Unthinkable - so it wasn't even considered. It was perhaps a meteorological phenomena?). They just ran fresh out of ideas. Freeze-framed twilight zone? Been there and done that too.

Someone also said (and theShadow said earlier in his 20 May post - and last year): "You are not only dealing with conflicting airspeed info, you are also presented with multiple spurious ECAM warnings and cautions which it is sometimes hard to ignore, also depending on the alternate law protection loss which itself can be further divided in two categories, or even direct law which would mean direct side-stick to flight control input without any load protection - leading to control overload." Isn't automation wonderful?

A pitot-static system's pneumatic airspeed data (the usable output product) relies wholly upon very accurate dynamic pressure and static (i.e. ambient atmospheric) pressure inputs - and the latter changes rapidly during a descent at 10,000fpm. No digitized sourcing of that info, it's all air pressure analogue. Falsify either one (via blockage or leak) and zoom or descend and the story will be ever more confusing. Birgenair and Air Peru 757's found that to be the case. For example, with a snap-frozen static pressure (at FZLVL) the airspeed indication will wind back from 250 knots to zero over as little as 3400 feet of climb at 250kts IAS. I think that the BEA is still trying to wrap their minds around that obscure fact here (Gallic and not Gaelic closed minds). They are also (possibly) assuming that the zoom was a result of pilot input and not an aerodynamic pitch-up..... i.e. as a result of (possibly) hitting Mach Crit with an A/P disconnect and a very nose-down trimmed horizontal stabilizer (@3 degs nose-up but increasing to 13 degs nose-up due to pilot's aft sidestick inputs after top of zoom climb). But do I actually think they hit Mach Crit? No, more likely it was the excessive elevator force gradient that kicked out the autopilot and kick-started the fatal zoom sequence..

Someone also said: "Direct law is there to give the pilot more direct control of the aircraft but it still has some protection to offer - BUT at the same time the protection on offer is only as good and accurate as the information provided to the computers involved. Much more info is needed before one can create a valid picture of what went wrong when it comes to the decisions the pilots made in the last few minutes of the flight." However the change in static pressure resulting from the zoom into ever more rarified air and the instinctive attempt to maintain level flight and use backstick to reduce the ever higher displayed airspeed indicated during the ensuing descent (subsequent to the zoom climb) are key factors dictating an inevitable entry into the unrecognized deep-stall condition. Additive to this was the dearth of info that they had to work with and little prior exposure to degraded flight control laws. And all this in night and in cloud.....

Confirmatory (for me anyway):
Did the pilot zoom climb the acft or was it caused by the automated mis-trimming in pitch? Perhaps this next statement in the report is a clue: [I]"The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb. The PF made nose-down control inputs and alternately left and right roll inputs."[/I] Perhaps the left and right roll inputs were his insufficient attempts to get the nose to drop (airline pilots rarely use more than 30 degs angle of bank due to the pax sensitivities - and in an Airbus? Perish both the thought and possibility....). When you've got a stuck elevator, or an aircraft pitching up of its own volition due to a runaway elevator pitch-trim, that's the way to go (i.e. roll the beast onto its wingtip to get the nose to drop - and drop flap). Pity they didn't think of that during the Jan 2003 Beech 1900 stuck elevator take-off accident at Charlotte NC.(52 degs nose-up at 1200feet agl).

So having read all the above, please feel free to shoot it all down. But ultimately, whether it's right or it's wrong, you have to ask yourself: "Is the training to combat automation anomalies and its inherent malfunction complexities adequate?" As someone else said: "In alternate law - is the amount of warning signals inhibited to the bare minimum necessary to keep the tube flying? i.e. you don't need a warning that the lights in the aft toilets aren't working - while busy with a stalling conundrum...?" Note how quickly the situation described above can become completely and incomprehensibly unglued. The debate yet to come is going to be ponderous and inherently evasive. The AF447 crew were caught out by a little known pneumatics phenomenon and reacting understandably to what they saw. They died clueless as to their actual predicament but I cannot bring myself to blame them. As they said: "We have no valid indications". They were right. Man can easily be defeated by automation. It's a burgeoning and futuristic problem. I can't shame them for being cheated of life by a system that's too conscious of cost and inconsiderate of consequence. The engineers and designers? Well they live in Never Never Land. If only the twain should meet....

On another subject, my post SR-111 invention in 1998 of satellite-uplinked recorder data is back in the limelight and I hope, with a vengeance. Wish it wasn't. But if you want to familiarize, just Google Iridian/Roadshow. Like all similar solutions to the long-winded AF447 saga, it's not as if somebody somewhere wasn't prescient. If we could just stop those holes in the Swiss cheese from aligning...... or more easily and quickly determine why they did.
____________________________________________________________ ___
Edited to add an afterthought:
a. I've heard two different qualified opinions as to whether the acft would have ended up in Alternate Law or ultimately transitioned to Direct Law. ???

b. "Just 20s after the captain returned to the cockpit, said the BEA, the thrust levers were set to the 'idle' position, with the engines delivering 55% of N1." i.e. Did the captain, upon entering the flight-deck, see the high (but fraudulent) IAS on descent and order the throttles to idle, understandably assuming a LOC existed and everything/anything BUT a stalled condition. You tend to take in and believe what you see on a first scan..... when the matter is urgent.

Last edited by TheShadow; 28th May 2011 at 04:42.
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Old 27th May 2011, 20:53
  #586 (permalink)  
 
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Air France is a third world airline with 3 hull losses since 2000....


I fly 332/343/345 and if the ride looks bumpy ahead I pull out the QRH and get the required N1 settings. Simple!!!!!! Even better - fly away from the big red bits!!! And - as the skipper - I'll be on the flightdeck for the awkward parts, such as flying through the ITCZ or monsoonal weather!!!!

Never give the aeroplane to the co-jos when it's going to be rough! As skipper you are responsible for the safe operation of the aeroplane. You cannot do this from the bunk!!!!!!!!!!!!!!!!!!!!!
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Old 27th May 2011, 20:59
  #587 (permalink)  
 
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A long but interesting input TheShadow!

However what ever happened to Pitch and power???
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Old 27th May 2011, 21:09
  #588 (permalink)  
 
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Speevy, that was my point. 5 degrees and CLB power is certainly not the thing to do at 39,000 in a 320 for example, yet it is the airbus procedure. The procedure was not developed for a cruise scenario... Hence it recommends 5 degrees with CLB power. Totally wrong thing to do, and if you don't believe me go and try it in the sim and see how long you stay above VLS when at max cruising level.
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Old 27th May 2011, 21:17
  #589 (permalink)  
 
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I read the report.
I read most of this discussion.

I don't understand.

There were cases where the pilots confused overspeed buffeting with a stall (or the other way round) which led to stick shakers and pushers. Is there no pusher on the AB? (maybe because the protections in normal law should always prevent a stall?) Hard to believe.

I was expecting to see an increasing IAS as they climbed (static decreasing while pitot remains constant as it is iced shut). The report does not mention that, so there was no indication of overspeed.

Stall recovery is the most basic thing that everybody who flies an airplane gets taught. I can't believe that they had three pilots that were unable to recognize the situation and do anything about it.

Very strage.
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Old 27th May 2011, 21:28
  #590 (permalink)  
 
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Soaringtheskies, go have a go in an Airbus sim (no stick pusher on Airbus), set it to nighttime with moderate/severe turbulence and then unreliable airspeed along with multiple ECAM messages - all at the same time. Given that you know what's coming you should be able to deal with it, however if you don't know it's coming then given those circumstances it certainly wouldn't be an easy job to deal with. People who say "fly the plane" are correct, but flying the plane won't necessarily be a concern if you don't realise there is an issue with it in the first place.

Edited to add: You can stall an Airbus, there have been several cases of people/mother nature doing it. Biggest problem with Airbus is it has lots of lovely protections (I.e. normal law) however whenever anything major goes wrong you lose them! Not a great thing to have happen and in many peoples opinions it is a serious design floor.
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Old 27th May 2011, 21:32
  #591 (permalink)  
 
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Ashling:

The stall warning is based on AoA so even with unreliable airspeed it will activate correctly. So the stall warning was telling them their AoA was too high. That indication was correct even if their airspeed indications weren't. Its also why you always honour a stall warning with unreliable airspeed.
But the Air Caraibes internal "Unreliable Airspeed" incident report (in somewhat similar circumstances to AF 447, though with significant differences, not least the end result) said [in French, mostly]:

"The PF was absolutely convinced that the two STALL alarms were inappropriate. He used his own judgement to discount the [checklist] phrase RESPECT STALL WARNING AND DISREGARD "RISK OF UNDUE STALL WARNING" STATUS MESSAGE IF DISPLAYED ON ECAM.
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Old 27th May 2011, 21:40
  #592 (permalink)  
 
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Shame White Knight wasn't on AF447 this thread wouldn't exist
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Old 27th May 2011, 21:43
  #593 (permalink)  
 
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Cool

Hi,

All on the deck .. battle station (not between ppruner posters but between AF and Airbus)

Le Figaro - France : AF447 : les avis d'Air France, de ses pilotes et d'Airbus

I let for you the translation work if needed.
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Old 27th May 2011, 21:48
  #594 (permalink)  
 
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These weren't the first airline crews to go all the way to the ground with the stick back. I just gave two briefings on Loss-of-Control Accidents and it seems to be a common theme.

I've also been researching cascading failures and multiple apparently random annunciations. We may have a bigger problem than it appears at first glance.



Goldfish
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Old 27th May 2011, 21:53
  #595 (permalink)  
 
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Cool

Hi,

TheShadow

Interesting .. but I read

and the handling pilot now had an instant unalerted surprise handful of an aircraft in Direct Law with nearly full nose-up trim and near to full power
The aircraft (announced by one of the pilot) go in alternate law and it's big difference when compare with direct law.
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Old 27th May 2011, 21:57
  #596 (permalink)  
 
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Hence it recommends 5 degrees with CLB power. Totally wrong thing to do
Sorry but I disagree, 5° CLB is the pitch and power data to get you away from troubles (if the safe conduct of the flight is impacted), then you set the pitch and power from the table off the cecklist...

If you are at 39000 and loose the airspeed indication all of sudden but still level, no change of airframe noise and altitude then you go for the table without setting 5° and CLB, therefore I cannot agree with you when you say that there is no airbus checklist for unreliable speed at cruise level, there is, and to me it's quite clear.
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Old 27th May 2011, 22:03
  #597 (permalink)  
 
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Thank you, TheShadow, very informative. I guess I come from a generation when "having to manually hand-fly an aircraft" was the preferred option.
If there's to be any real progress, I guess we need to examine what training led to the 'human factors' error they made. From my humble flight safety background, it usually turns out to be human factors rather than pilot error.
Next time I fly the pond, I'm tempted to fly it myself in a puddlejumper(again).
p.s. there will only ever be one 'procedure' for everything; it's called "airmanship".
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Old 27th May 2011, 22:26
  #598 (permalink)  
 
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Stabilizer trim to 13 degrees up?

Sorry if this has already been brought up, but why would THS go from 3 to 13 degrees during the interval 2:10:51 (red ball 5) and the next entry 50 seconds later, and stay there for the next 4 minutes until the data stops?

The way I read it is that the AP had disconnected by this time, so was some other system automatially increasing THS in the 2:10:51 interval?

Last edited by thcrozier; 28th May 2011 at 00:03. Reason: Clarification.
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Old 27th May 2011, 22:27
  #599 (permalink)  
 
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But here's a clue. In the subsequent descent with static pressure increasing and the pitots still blocked?, even though the airplane was actually stalled (complete with stick-shaker) the indicated airspeed would be increasing alarmingly - courtesy of increasing static pressure. That's my guess - and it's anyways a physical fact, Been there and done that trick with frozen trapped water in the static lines (i.e. the opposite effect of trapped dynamic pitot pressure). There's also a report on the Irish Accident Board's site about a 747 on a test flight with uncapped static lines due maint error. It's an elucidating gaelic tale that shows just how confusing the pitot-static scenario can be. See below for how much a 1000feet of altitude change is worth in terms of additional "displayed knots". Ask any instrument technician. That's what I did. He'll demo it for you on his test-bench.
Well, as an example of how confusing it is, I happen to have my Jeppesen basic IFR book here, and it seems to say the opposite:

The second situation occurs when both the ram air inlet and drain hole become clogged, trapping the air pressure in the line. In level flight, the airspeed indicator typically remains at its present indication, but no longer indicates changes in airpseed. If the static port remains open, the indicator will react as an altimeter, showing an increase in airspeed when climbing, and a decrease in airspeed when descending. This is the opposite the normal way an airspeed indicator behaves, and can result in inappropriate control inputs because you will observe runaway airspeed as you climb, and extremely low airspeeds in a descent. This type of failure can be very hazardous because it is not at all obvious when it occurs
As an aside, what's wong with a good, old-fashioned idea of having a small red or yellow ribbon on a small stick which is bolted just outside cockpit window? Shine your flashlight out at it and it will give you a very fast indication of what direction the air is going past the airplane.
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Old 27th May 2011, 22:34
  #600 (permalink)  
 
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Deep stall recovery

So it seems this plane was into a deep stall with nose up 16 degrees. Angle of attack 40 degrees. Vertical speed 110 knots. Horisontal speed low(60knots) Seems to me that the only option to get the plane out of this condition would be to get the nose of the plane into the direction of movment. Even full trottle would not be able to make a horisontal speed high enough to give a flyable angle of attack. So the only option would be to get the nose down in a steep dive.

I suggest using the rudders hard to one side to completely stall one wing get the plane to flip over in a spin would acctually help to get the nose down fast and then get the correct angle of attack back. An other option to get the plane to flip over would perhaps to give a high trust on only one of the engines - to create the nessesary rotation to loose all lift in one wing and get the nose.

I suggest even taking trottle to idle would not harm at all (once the spin is there - at suficcient altitude of course) - It might simplify recovery not have to deal with those nose-lifting forces and to rapid increasing speed diving with the nose to the ground. Simply get the nose of the plane into the direction of movementwould exchange height for flying speed rapidly and solve the problem. .

Also - I would like to know if comercical pilots ever practise stall recovery in a real plane in real air. I have practiced stall/spinn from 3000 feet in a sail-plane several times - and suggest practice of this method in a sailplane could be valuable even to comercical pilots.

The initial stall-spinn does not involve high G-forces. The G-forces will be felt when at high flying speed with the nose to the ground will slowly lift the nose back to horisontal (and then add some trottle to keep a normaliced flight) In my sailplane typically 2-3 G.

I'm not talking about "what to do when you get the stall-shaker alarm" but - what to do when your allredy deep into a stall - but horisontal wings - and nose up.

I also realize that there may be some flaws to my argument here- Im not an expert in this area.
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