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AF447

Old 3rd Jul 2009, 09:18
  #2821 (permalink)  
 
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Hi all,

I've been lurking on here for quite a while but I though I might post on a though I had after reading all the posts on here and the report yesterday.

First off I'd just like to say I am not a pilot and I dont work in civil aviation. However, I am an engineer with 10 years experience and an aerospace background. Several years back I took part in 2 crash investigations regarding unmanned military aircraft.

The indications seem to be that the aircraft went into the sea at a high rate of speed but also it would seem it lost considerable altitude in a very short time. This does not seem consistent with the fact the aircraft met the ground in one piece - how could so much altitude be lost so quickly?

My suggestion is that the pitot tubes could have failed (iced up) quite some time before the accident or any indication of a fault. Suppose all three tubes failed at approximately the same time holding the readings for cruising altitude and speed. The consistency in readings may have got past the computer which may not have raised the fault.

In this eventuality is it possible that the auto pilot could have continued to operate on false information leading to gradual loss in altitude over a relatively long period and hence this was not noticed by the crew or ATC which would get altitude from the aircraft via secondary radar.

The pitot fault messages could have been caused as the pitot tubes began to de-ice as a result of the warmer air at lower altitude. If they did not de-ice at the same time this would cause the disagreement which initiated the fault.

After that the crew would have had a high workload and very poor situational awareness due to the instrumentation fault. Perhaps the presence of weather also blocked out the moonlight making any visual cues difficult to see.

Could the crew have flown into the sea at high speed if they had much less altitude than expected? Maybe the tail first impact suggests the only saw the sea at last minute and pulled up resulting in the tail striking the water.
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Old 3rd Jul 2009, 09:23
  #2822 (permalink)  
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I'll take up only two, straightforward, points and leave the rest to m'learned friends.



.....ATC which would get altitude from the aircraft via secondary radar
Have you looked at where this occurred? What ATC radar?



Could the crew have flown into the sea at high speed if they had much less altitude than expected?
Do you not think they would have noticed the loss of >30,000 feet of altitude?
 
Old 3rd Jul 2009, 09:30
  #2823 (permalink)  
 
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BOAC -- they didn't state anything of the sort. They had "ligne de vol".
They also provided their evidence.
From the evidence available, they could state two things:

A. The attitude of the aircraft relative to water at the moment of impact.
B. The vector of the aircraft at impact.

A. was more or less cabin level to the horizon (ligne de vol)
B. was far from gentle and largely vertical.

That's it.
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Old 3rd Jul 2009, 09:31
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I have been thinking on similar lines to Safetypee’s post 2839.

There have been a number of references in this thread to the QRH procedures for flight with unreliable airspeed. Some of the comments seem to imply this is an easy task- just set the power, maintain the pitch attitude and it will work out. I am not convinced.

This procedure may be fine in stable weather situations, but all the evidence suggests AF447 was encountering far from benign conditions.

Let us assume that around the major Cbs in the ITCZ there were significant horizontal and vertical windshears, a not implausible scenario. An encounter with a rapidly increasing headwind would result in a rise in airspeed, which would need to be countered by a reduction in thrust to avoid a potential overspeed, but the crew would have no means of identifying this need and the speed rise would go unchecked..
.
If the crew were attempting to use GPS or inertial groundspeed as their cue (because there was no alternative) they would likely increase thrust instead of reducing it . Hence the risk of an overspeed would be greatly increased.

Now run the converse scenario of an increasing tailwind. Airspeed falls, crew unaware ,so do not take corrective action, ground speed increases, so thrust is reduced, result is underspeed.

Add in a further possibility. If at the instant of A/THR disconnect, the system had already reduced or added thrust to counteract a speed excursion, crew action to set the QRH reference power could actually exacerbate the speed error.

In the vast majority of situations, one would expect these effects to be minor, transient and hence containable. Is it possible that in the weather situation in which AF447 found itself, the effects were major and cumulative, to the extent that a critical underspeed or overspeed
occurred ?

Even if this situation did not take place, it seems to me the crew had a major task on their hands that could have reduced their capacity to manage any other.event that might have occurred. It may not be necessary to speculate on the implications of Airbus Alternate Law -
the potential could be the same for all types. And I keep asking myself how well I would have coped.
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Old 3rd Jul 2009, 10:00
  #2825 (permalink)  
 
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A other analyse ..

Hi,

Eurocockpit - Archives

Unfortunately it's in french.
The use of a translator (like Google) may help but it's not allway accurate.
For one who understand french .. it's nice to read.

Bye.
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Old 3rd Jul 2009, 10:03
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In this post http://www.pprune.org/rumours-news/3...ml#post5012151 you can see that the speed over ground was almost constant up to 2:10.

From that I would dare to conclude that the altitude was constant too.
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Old 3rd Jul 2009, 10:18
  #2827 (permalink)  
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Originally Posted by Dinger
They had "ligne de vol".
- yes, but it appears to be an unfortunate expression with more than one meaning, and I feel they should have been more 'accurate'. We all 'deduce' the meanings from logic, but it is all about 'translation'

This from Google - Dictionnaire des sciences de la terre By Magdeleine Moureau, Gerald Brace

flight line: ligne de vol trace sur une carte de al trajectoire a suivre par un vehicule aerien

It doesn't help when even the French cannot agree! (Excuse the missing accents).

I have come to expect careful wording in accident reports, and to talk of high vertical 'acceleration' when presumably they mean deceleration (ie a 'hard impact') I find strange. EG do they mean they deduce it was Accelerating rapidly towards the water or is it as we actually 'understand' it?
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Old 3rd Jul 2009, 10:38
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Question ACARS Position Reporting

From the English BEA report p45:
"The first position message (AOC type message) was transmitted on 31 May at 22 h 39. On
1st June at 2 h 10 min 34, the last position received was latitude +2.98° (North) and longitude
-030.59° (West). The position transmitted was the aircraft’s FM position which, in normal
conditions, is close to the GPS position."


I am surprised by the news that the aircraft was set up to provide regular 10 minute AOC position reports via ACARS and yet no procedure appears to have been in place at AFR ops to react to the loss of these regular messages.

Last edited by starliner; 3rd Jul 2009 at 11:03. Reason: Punctuation
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Old 3rd Jul 2009, 10:38
  #2829 (permalink)  
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scouselander

Just not feasible for any number of reasons not least because pitot tubes don't feed the altimeters, static ports do.

As for the rest, a lengthy explanation would just derail this thread and there's been too much of that already.




YHM
 
Old 3rd Jul 2009, 11:05
  #2830 (permalink)  

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BOAC

They had "ligne de vol".
- yes, but it appears to be an unfortunate expression with more than one meaning, and I feel they should have been more 'accurate'
Nothing unfortunate, it's in fact a rather accurate description of the aircraft attitude.
To illustrate its meaning, just imagine a tail dragger -a DC-3, for instance ; first it sits on its tail wheel and as it accelerates, the tail goes up from a forward pitch control input. There ! the aircraft is then "en ligne de vol".
That description is still used in flying clubs as to teaching take offs.
It doesn't help when even the French cannot agree!
There are two categories of Frenchmen :There are the French aviators and there are the French non aviators. And among them there are old French aviators and not old French aviators. Fortunately there are old French aviators who have French aviators' sons and daughters....

oleole
From that I would dare to conclude that the altitude was constant too.
It would have been a lot easier to read the report and see where they were cleared to FL 350 and also read their communications transcripts.

starliner
I am surprised by the news that the aircraft was set up to provide regular 10 minute AOC position reports via ACARS and yet no procedure appears to have been in place at AFR ops to react to the loss of these regular messages.
Good point. Problem is that these reports overlay on the incrusted routes on a screen.
First there are airplanes sharing the same route at about the same time.
Second, the dispatchers have to provide a lot of OPS requests on some 120 (a guess) long haulers at any given time.
Third, it is not really a monitoring system but a quick way of identifying who is talking, where he is and what his/her needs could be.
The fact that AF447 and AF59 were on the same route at the same time was, IMO, enough to hide AF447's position, unless the dispatcher specifically separates both traces from each other.
Another factor could also be that between 0330Z and 0415Z, there could have been a shift change at dispatch, with the normal hand-over tasks to the new dispatcher(s).
That the system could be improved for an irregularity alerting program is, again IMO, an absolute necessity.
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Old 3rd Jul 2009, 11:11
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BOAC

From a technical point of view they are quite right to use the term 'acceleration'. Acceleration is a change of velocity. It doesn't matter whether its an increase or a decrease (deceleration as you call it), from a technical point of view it is still referred to as 'acceleration'.

The situation you describe earlier, cyclic increase then decrease of attitude and altitude is fugoid oscillation. If the aircraft had been experiencing this then the flat attitude would have placed it near the bottom of one such oscillation, where it would have had a relatively high forward speed. The BEA appear to suggest it had low forward speed at impact.
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Old 3rd Jul 2009, 11:28
  #2832 (permalink)  
 
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DingerX,

At the risk of being fined for extreme pedancy I note that a vector is a three axis plus magnitude item. They only defined approximations for one of the three (the vertical axis) and the magnitude. They did not define more than the rough plane (no pun intended) defined by the other two.

JD-EE
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Old 3rd Jul 2009, 11:40
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wondering

if the cbin rate was a climb and the crew didn't don their oxygen masks, couldn't they have become incapacitated *hypoxia* and then the plane, with its computer system failing due to pitot icing finally went out of control in the natural turbulence of a storm?

the more I read, the less I know.
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Old 3rd Jul 2009, 11:45
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It is entirely possible that an excess cabin altitude could have incapacitated the pilots. However, one would expect an ACARS 'Cabin PR : Cabin Excess Altitude' message if the cabin alt had risen to dangerous levels (ECAM triggers this warning at 9550ft plus or minus 350').
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Old 3rd Jul 2009, 11:52
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now retired PJ2

You seem a wonderful source of knowledge PJ2. I am sorry to hear that you are retired. I would love to hear that Airbus or Boeing or whoever would grab you as a fantastic teaching authority. That is the same for all other retired captains on this forum. The airline industry should be using you big time!!!
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Old 3rd Jul 2009, 12:20
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Why ?

Can any one figure out why this aircraft ended up in this position and situation that accelerated the spiraling chain of events. Looking back at the satellite weather conditions in the area, I don't think any pilot in his right mind would plow along on the track the aircraft followed into disaster.

Why was the captain at rest, if he and the crew had done a thorough flight briefing and known that their track would take them through bad weather at a specific time window on this flight ?

How can two radars miss the weather if they were used properly unless the selector switch was turned to off at some stage !

I have been flying for 41 years and currently fly this amazing aircraft but I have always maintained a very cautious attitude to both my own and this aircraft's limitations, this attitude has served me well but I have noticed a complete state of complacency show its ugly head as far as young pilots sitting in the right seat or acting as cruise pilots. It is not uncommon for me to return from rest to find laptops out on the pull tray obscuring flight instruments or sorry animated discussions about work and pay conditions while the aircraft does her own thing an receiving looks of disbelief when voice my concern that monitoring aircraft flight performance and weather conditions mean just that and not getting sucked into complacency and side distractions. I am looked on by some crews as a relic and behind the times !

I have also noticed a general lack of respect for the power of weather and convective activity.

I hope positive lessons would be learned from this disaster and SOPS will start covering pilot cruise monitoring duties more extensively.

We have a duty to ourselves, our customers and this profession, to be vigilant at all times regardless of the level of automation available to us. Situational awareness and good judgment have never been more needed.

This chain of events for this accident seem to have started at flight briefing.
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Old 3rd Jul 2009, 12:28
  #2837 (permalink)  
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[quote=Icarus]Can any one figure out why this aircraft ended up in this position and situation that accelerated the spiraling chain of events. Looking back at the satellite weather conditions in the area, I don't think any pilot in his right mind would plow along on the track the aircraft followed into disaster.

Do you know the flight path "the aircraft followed" for a fact?

Why was the captain at rest, if he and the crew had done a thorough flight briefing and known that their track would take them through bad weather at a specific time window on this flight ?

Do you know he was?

How can two radars miss the weather if they were used properly unless the selector switch was turned to off at some stage !

Do you know they did 'miss' it?[/quote]

I have no issue with the rest of your post.
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Old 3rd Jul 2009, 12:50
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Almost 1.5million views, 150 pages (plus those deleted) and although I may stand corrected, I don't recall anybody offering a theory anywhere near the preliminary report i.e. the a/c dropping out of the sky, in once piece, more or less straight and level with not much forward speed. I am also surprised at the lack of interest on the Yemenia thread, which even though as catastrophic has only attracted minimal media and PPRUNE interest.

This tells me that a) the BEA have got it wrong or b) even with all the experience of the contributors on this site, there is still some pretty important stuff that remains unknown in terms of airmanship, aerodynamics and structural integrity of a/c. Having worked in aviation for a very long time, I like to think that the answer is a).

The biggest bird I fly is a Twin Comanche, which is why I am an interested viewer only and choose to learn and not to comment... normally!
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Old 3rd Jul 2009, 13:01
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On the condition of the bodies:

The BEA report only references the 30 bodies recovered by the French frigate Ventose. The other 20 bodies were recovered by the Brazilian Navy, and the initial body recoveries were by the Brazilian Navy.

The BEA characterizes the bodies recovered by the Ventose as "clothed and relatively well preserved." There is no characterization of the bodies recovered by the Brazilian Navy.

There is a possible undertone of frustration with the Brazilian authorities with respect to the bodies. Early on, the French complained about being excluded from the team performing the autopsies. The BEA report hints that the French are still in the dark, stating that the Brazilian authorities have yet to provide any autopsy results. (Some bodies have already been released to families for burial.)

The BEA report contains no information on how many of the bodies, well-preserved or not, are already identified. Once identified, passengers can be matched with assigned seats, and this can be a valuable data-point with respect to how the plane impacted.

And then there is the damage done to the VS by the Brazilians in the course of recovering it....
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Old 3rd Jul 2009, 13:21
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Like many others in this thread I have been lurking for some time but now I feel a need to post. I have an extensive background in emergency response, safety management and incident investigtion.

This thread is full of assumed minor detail and subsequent rather pointless analysis. But it seems to me there are some helicopter view issues which I feel would benefit from broad discussion and I feel are the real issues here.

I don't get the vibe that all that many here understand safety and reliability engineering. The first issue is my impression is that there is a common mode failure issue which deserves greater attention. Regardless of the real cause of this incident, my interpretation is too much depends on elements that can fail in the same way. Does anyone have a comment on that?

The second issue is that I am amazed it took so long to initiate an emergency response. While it might not have made a difference to lives saved, how can that be the case?

I expected more from the airline industry, I assumed things were more robust and I have lost some confidence.
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