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AF447 wreckage found

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AF447 wreckage found

Old 29th May 2011, 06:56
  #781 (permalink)  
 
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mac the knife,

Is this supposed to be some kind of defense?

These highly paid pilots are expected to be able to handle such situations with ease. Ok so wow, they had to fly in the middle of the night, over the ocean, it was no doubt cold outside and windy and perhaps the seats were so comfortable that they felt sleepy and staring out of a window for hours at blackness is boring. Oh and we must sympathize that flashing lights are just too damn distracting.

Hello? They are supposed to be professionals. If they can't do their duty because of the above factors then they have no place in a cockpit. If i pay 500 euros for a flight i damn well expect the pilots do be competent enough to handle whatever inconveniences or distractions that might occur during their duty. Over 200 lives were lost because it seems the pilots didn't know what to do once the autopilot stopped flying the plane.

Anyone with a little bit of training on simulators can fly an airbus using the autopilot for 99% of the flight including ILS landing. But these pilots are paid for when the **** hits the fan and for their expertise, skills and judgement in those rare situations when the plane doesn't just fly itself for you.

Given what we know thus far, i expect trials will find the pilots criminally negligent and there will be huge compensation for the families.

Last edited by wafelbolletjes; 29th May 2011 at 07:07.
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Old 29th May 2011, 07:11
  #782 (permalink)  
 
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Stabilizer or De-Stabilizer? It's Becoming a Focus of the AF447 inability to recover

As some technical "niceties" about the auto-trim system starts to emerge, it's beginning to sound as if the vagaries of the auto-trim system in respect of Airbus Law Change philosophy were instrumental in the inability of the AF447 crew to recover from the type of stall that they'd entered. i.e. they may have been victims of the circumstances of their stall entry scenario. To explain:

a. During the zoom climb to FL380 (in Alternate Law) the auto-trim transitioned from 3 deg N/up to 13 degs n/up (near to, if not max nose-up THS trim for the type).

b. Upon entering the stall ballistically and starting its "deep"-stalled descent, the aircraft would have been (and remained) in Abnormal Law, with the auto-trim inop and the trimmable horizontal stabilizer (THS) therefore locked at 13 degs nose-up..... unless it was to be manually changed by the pilot (and we now know that it was not).

c. The engines were at TOGA at this stage, so we have the pitch-up effect of TOGA power plus the THS "stuck" (i.e. de-automated) at 13 degs nose up.... both tending to pitch-up and support a stall continuance..... no matter what the pilots did (unless they were to change the acft configuration somehow - aerodynamically or CofG wise).

d. Airline pilot exposure to stalling tends to concentrate upon the approach to the stall and recovery (i.e. avoidance) with minimum altitude loss. In that stock standard scenario, one of the primary and persistent preliminaries in the incipient stall experience is the airframe buffeting and stick-shaker progression. This is de rigeur in a standardised level 1kt/sec deceleration towards a level 1g stall and is the cue for the trainee to take recovery action. However, if one enters a stall ballistically at high altitude, will there be any buffeting? The AoA system will issue a stall warning but is this against a distracting background medley of other aural alarms? Stall recognition and realisation then becomes an obscurity of the first order.

So the question now becomes: "What would be required to un-stall this aircraft (now in Abnormal Law) if there is insufficient elevator authority at 13 degs nose-up THS to get the nose down (and thus air over and across the wings and tail), during a stall locked in at 40 degs AoA (as predicated by their entry config)?" One answer might be: "Idle the power" (and this was done soon after the captain re-entered the flight-deck, possibly because he'd just misinterpreted their predicament as a L.o.C., based upon a quick scan). Another might be: "Manually run the trim" (i.e. not something that comes naturally to an Airbus pilot - particularly not if he's unclued and quite unaware that the 13 deg nose-up THS is now his basic problem). A pilot's normal cueing to adjust trim is that the airplane is "out-of-trim" and tending to deviate from a chosen flight-path i.e. not a player in this deep-stall scenario.

Three questions: 1. "Will the pilot be aware that he's in abnormal Law? (and the portents of that)" The answer might well be: "Probably not" (there's nothing to promote awareness of this being the case i.e. no aural annunciation - and thus we arrive at: what now needs to be done that's essential for recovery?)
2. "Does the elevator alone have sufficient authority to unstall the wings at max power or at idle?" The answer is probably not, at least not while the superior trim authority of the THS at 13 degs n/up holds sway.... and particularly not whilst at TOGA power.
3. "Why doesn't the elevator have sufficient authority to unstall?"
The whole design premise of the THS is to reduce trim drag and allow the elevator to become more of an active trim and less of a primary flight control. This ideation works well 99.99% of the time and it's used in all models of airliners to some degree. They need the capability of coping with large CofG ranges to accommodate loading, fuel burn-off and configuration changes. Some aircraft augment this capability with tail-located fuel trim-tanks. However this minimalistic elevator design feature in the A330 apparently won't "work" in the progression of events that AF447 underwent.

So are Airbus elevator throws and areas (i.e. authority) an under-design or does the THS have undue authority? That becomes the question here as we switch our attention to not blaming the pilots but agonizing over possible Airbus design deficiencies. But before we look into that, we need to pose the question: "Were the AF447 pilots aware that they were locked in an aerodynamic stall?" I'd suggest that they were NOT..... mainly because of the circumstances of their entry being wholly unfamiliar..... and that medley of aural alarms mentioned earlier that had overloaded their capacity to assimilate transient info. It's called cognitive disequilibrium, an idiosyncratic need to ignore or de-prioritize - a close relative of cognitive dissonance (a tendency to rigorously deny or disbelieve), two behavioral paradigms to which professional pilots are prone. One final thought, centering upon human factors. When the captain entered the cockpit and tried to take it all in at a glance one of the things he would've missed, because of its positioning, is what the pilot's input was on his sidestick. With a yoke (thinking of Egyptair MS990 here) it's visually apparent that what's afoot is directly related to pilot action. Food for thought.

Are there any precedents in the Airbus incident and accident annals? There's the Air New Zealand A320 test-flight crash and the Tarom Airbus near accident on ILS finals at CDG..... that spring to mind.

It's worth citing an extract from the Tarom incident: "Under the aerodynamic effect of this THS deflection (of 13 degs) and under the mechanical effect of thrust, the aircraft was thus subjected to a nose-up force that could not be controlled by elevators. It rapidly assumed an extreme pitch attitude and angle of attack.

There may be others. The 1994 crash on go-round of a (non-FBW) A300 at Nagoya? (link). Para 4.2.b of this link lists 6 Airbus incidents and one B747 involving pitch-trim anomalies. An extract from that Nagoya narrative might help emphasize the sometimes inordinate power of a THS in some circumstances: After the PF inadvertently pressed TOGA on finals,

"The autopilot automatically went into GA mode, and this would have shown on the primary flight display (a very vague alert really). The aircraft was flying 18 degrees nose-up, normal for a go-around, but the FO was pushing heavily on the yoke to get the nose down. He was meeting heavy resistance, a design indication on almost all airplanes that that his manual commands were in conflict with the autopilot. For nearly 20 seconds, as he applied down-elevator, the autopilot moved the trimmable horizontal stabilizer (THS) in the opposite direction to keep the nose up. At T+30, THS reached maximum nose-up; at T+42, the autopilots were disengaged. Pilot C asked for autothrottles engaged and took control, increasing down elevator to full deflection as the aircraft began climbing. Alpha-floor (an Airbus automatic protection mode) triggered at T+50 from excessive AOA. Alpha-floor triggered maximum thrust for climb-out, but that added thrust in fact increased the nose-up attitude to 52.6 degrees (one may surmise that the thrust centerline is below the rotational center of the airplane, and at low speed there is not much aerodynamic force to maintain resistance to this rotation). (52.6 degrees is very steep. A high-friction granite rock face of this angle would nevertheless be considered a technical rock climb.) C disengaged alpha-floor by retarding thrust and tried to get the nose down again with trim. Airspeed had dropped to 78 kt., the aircraft stalled at 1,800 ft, and control was not regained before it hit the ground."

If the BEA Inquiry into AF447 heads down this well-trammeled path towards THS excess authority and control law anomalies in stalls, Airbus is going to have to do the old quickstep that they've always done so well - in order to avoid changing physical design. No doubt it will take the form of a circuitous software patch to the control laws and/or yet another aural alarm and cautionary bulletin.
Edited to add:
However, despite all of the above, there is no denying that “no clear-cut stall recognition and persistent warning” is the apparent deficiency that put AF447 into the Atlantic. Recognizing that the overwhelmed pilot can become clueless in a time of great stress, perhaps aural alarms should become aural admonitions: as in “Stall Warning. Reduce angle-of-attack and trim nose-down for recovery”

Last edited by TheShadow; 29th May 2011 at 07:35.
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Old 29th May 2011, 07:19
  #783 (permalink)  
 
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Originally Posted by wafelbolletjes
Two words describe best the action of the pilots and in particular the captain who thought it a good idea to take a break in the middle of the worst area of weather: criminal negligence.
Well I think it is criminally ignorant and stupid to post such a comment . Do come back later once you know what you are talking about. In the meantime stop wasting my time reading such crap.
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Old 29th May 2011, 07:28
  #784 (permalink)  
 
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When the media, AF, the investigation and the courts start using those 2 words, i expect an apology ZBMAN.
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Old 29th May 2011, 07:28
  #785 (permalink)  
 
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Maybe they need to hire qualified pilots and let the 250 hr wonders pay their dues and do something doing actually flying for a while before they get in the right seat.
The more senior f/o had over 6600 hours of which 2600 are on type. Junior f/o had more than 3000 hours!

A newbie 250 hour wonder probably would have had better CRM, more recent and genned up on the flight control systems.
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Old 29th May 2011, 07:34
  #786 (permalink)  
 
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Excellent analysis from The Shadow.Frightening though.I looked at this accident from the POV of a pilot of a real plane that does what you ask and never does things subtly without you knowing only to leave you unprotected at the worst moment possible.My mistake.So auto trim is not so cool after all.I wont comment further because it will be bad for my blood pressure.I see the pilot's predicament in a new light though after the Shadow's post and I think it is definitely mitigating.
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Old 29th May 2011, 07:42
  #787 (permalink)  
 
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While TheShadow's points may be valid, they don't excuse the pilots for not even trying to point the plane's nose downwards (for the last 3 minutes). It also doesn't excuse the pilots for not realizing that the plane was in fact stalled. If it's going down at 10k fpm with nose up attitude and full throttle then, duh, it must be stalled.

If the pilots had however been pushing forward on the sidesticks and screaming about how the plane was stalled on the CVR then we can solely lay the blame on airbus design flaws. But that's not the case. I won't comment again because it is clear the pilots here will never lay the blame on fellow pilots. I'll no doubt be labelled an idiot but at least i am not an idiot responsible for the death of over 200 innocent adults and children.
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Old 29th May 2011, 07:43
  #788 (permalink)  
 
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ZBMAN

Fully agree with you.

WaffelPlease go back to your Flightsim and enjoy.The problem is this is an open forum and then we waste time reading loads of crap here.
It's tiring, boring to try to explain the basics to people like you, sorry.

BTW, congrats on the brilliant post "The Shadow"! You counterbalance at least ten of the bshitters.
Keep up the good job.
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Old 29th May 2011, 07:49
  #789 (permalink)  
 
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Will the pilot be aware that he's in abnormal Law? (and the portents of that)" The answer might well be:[COLOR=SlateGray][I] "Probably not" (there's nothing to promote awareness of this being the case i.e. no aural annunciation - and thus we arrive at: what now needs to be done that's essential for recovery?)

AH no??? The PF announces Alternate Law when he takes manual control of the aircraft. It is in one of the first lines in the BEA communication !!!

2. "Does the elevator alone have sufficient authority to unstall the wings at max power or at idle?" The answer is probably not, at least not while the superior trim authority of the THS at 13 degs n/up holds sway.... and particularly not whilst at TOGA power.

In ALT LAW with AP an AT off there is virtually no Stall protection left. The THS goes where the pilot wants it to go. It simply responded to the pitch-up inputs by the pilot to 'help' him go where he wants. Had he made pitch-down inputs afterwards it would simply have gone in the other way, although it would take a continuous pitch-down input for some time.
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Old 29th May 2011, 07:55
  #790 (permalink)  
 
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anyone else feel that this post is totally pointless ???

Everyone posting their own take on the situation then using it to back their own particular hobby-horse (AB, Boeing, manual flying, anti-French, conspiracy theorists, etc etc ) and then slaggong off everyone else

really depressing TBH
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Old 29th May 2011, 07:59
  #791 (permalink)  
 
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To TheShadow:
Three questions: 1. "Will the pilot be aware that he's in abnormal Law? (and the portents of that)" The answer might well be: "Probably not" (there's nothing to promote awareness of this being the case i.e. no aural annunciation - and thus we arrive at: what now needs to be done that's essential for recovery?)
As the voice recorder proofs, they knew very well, see the report.
2. "Does the elevator alone have sufficient authority to unstall the wings at max power or at idle?" The answer is probably not, at least not while the superior trim authority of the THS at 13 degs n/up holds sway.... and particularly not whilst at TOGA power.
3. "Why doesn't the elevator have sufficient authority to unstall?"
The whole design premise of the THS is to reduce trim drag and allow the elevator to become more of an active trim and less of a primary flight control. This ideation works well 99.99% of the time and it's used in all models of airliners to some degree. They need the capability of coping with large CofG ranges to accommodate loading, fuel burn-off and configuration changes. Some aircraft augment this capability with tail-located fuel trim-tanks. However this minimalistic elevator design feature in the A330 apparently won't "work" in the progression of events that AF447 underwent.
The PF didn't try to use the elevator to unstall, their input was "nose up", see the report.

A much more realistic explanation is http://www.pprune.org/rumours-news/4...ml#post6479529.
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Old 29th May 2011, 08:05
  #792 (permalink)  
 
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Perhaps they reacted to windshear, rather than stall.

Full back stick and TOGA, then hold both until the aircraft flies out of the problem.
I think that this is an excellent comment.

I know I'll be told that one can't get the sort of low level windshear that demands such aggressive response at altitude, but once the mindset has been made, and all sorts of confusing information is being thrown at one, then I can see the scenario that occurred being played out.

I'm glad I wasn't there.
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Old 29th May 2011, 08:05
  #793 (permalink)  
 
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I really wasn't going to reply again but... like a tickle...

fullforward, people like me? I have a Master in aerospace engineering and am working on my PhD (in the area of aerodynamics). I don't appreciate being labeled 'people like you'. I probably know more than you about stalls.

The fact is, and this is an indisputable FACT, the plane was fully functioning and the pilots crashed this plane into the ocean. Talking about auto-trim, psychological anomalies or design flaws are the conspiracy here, not me stating the obvious that the pilots didn't know how to fly the plane. Don't shoot the messenger.
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Old 29th May 2011, 08:09
  #794 (permalink)  
 
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A good post shadow. Interesting in that on a few occasions in the little bus on a normal go around the a/c some times over pitches with the speed reducing below VLS Airbus then had to change some control protections to include a mod to the speed reversions. Having said that disconnecting the auto guidance & applying some fwd stick puts things back to normality. I have not had that problem with the big bus. However a pilot must realise that the automatics are not infalable just like pilots aren't either.
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Old 29th May 2011, 08:12
  #795 (permalink)  
 
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I have a Master in aerospace engineering and am working on my PhD (in the area of aerodynamics).
but, wafelbolletjes, with all respect, are you a pilot?

I probably know more than you about stalls.
That may, or may not, be true but that doesn't mean you would/could do any better than these pilots in the situation they found themselves.
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Old 29th May 2011, 08:13
  #796 (permalink)  
 
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When the media, AF, the investigation and the courts start using those 2 words, i expect an apology ZBMAN.
He won't owe you one. This isn't about you turning out to have been right or not. This is about you jumping to conclusions and condemning people without the knowledge and the facts to back it up.
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Old 29th May 2011, 08:17
  #797 (permalink)  
 
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but, wafelbolletjes, with all respect, are you a pilot?
Please, refrain from ad hominem attacks, and focus on arguments instead.
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Old 29th May 2011, 08:24
  #798 (permalink)  
 
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Will the pilot be aware that he's in abnormal Law? (and the portents of that)" The answer might well be: "Probably not" (there's nothing to promote awareness of this being the case i.e. no aural annunciation - and thus we arrive at: what now needs to be done that's essential for recovery?)
AH no??? The PF announces Alternate Law when he takes manual control of the aircraft. It is in one of the first lines in the BEA communication !!!
He's talking about Abnormal law, not Alternate law. The relevant difference here being autotrim not working in Abnormal law.
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Old 29th May 2011, 08:26
  #799 (permalink)  
 
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Please, refrain from ad hominem attacks, and focus on arguments instead.
abovethesky, it wasn't an attack, merely a request for information!

It is relevant to the matter under discussion. Whilst having every respect for those having technical qualifications far superior than a mere mortal pilot, such as I, unless you have done or are doing the job as a pilot you really have little appreciation of what these pilots were faced with.

There is too much condemnation going on here of the pilot's actions, especially when we don't know all the facts.
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Old 29th May 2011, 08:26
  #800 (permalink)  
 
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To TheShadow:
Your analysis is based on wrong assumptions:

Three questions: 1. "Will the pilot be aware that he's in abnormal Law? (and the portents of that)" The answer might well be: "Probably not" (there's nothing to promote awareness of this being the case i.e. no aural annunciation - and thus we arrive at: what now needs to be done that's essential for recovery?)
They know very well, see the repport.
2. "Does the elevator alone have sufficient authority to unstall the wings at max power or at idle?" The answer is probably not, at least not while the superior trim authority of the THS at 13 degs n/up holds sway.... and particularly not whilst at TOGA power.
3. "Why doesn't the elevator have sufficient authority to unstall?"
The whole design premise of the THS is to reduce trim drag and allow the elevator to become more of an active trim and less of a primary flight control. This ideation works well 99.99% of the time and it's used in all models of airliners to some degree. They need the capability of coping with large CofG ranges to accommodate loading, fuel burn-off and configuration changes. Some aircraft augment this capability with tail-located fuel trim-tanks. However this minimalistic elevator design feature in the A330 apparently won't "work" in the progression of events that AF447 underwent.
The PF didn't even try nose down. He wanted nose up. So all the speculation whether we would have been capable of bringing the nose down (elevator, trim) is mood.

The analysis of Flight Safty makes much more sense.
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