More on AF 447

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VC10
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Re: More on AF 447

Post by VC10 »

Chris,

I have just re-read the link at the top of this thread and it makes no mention of autothrust dropping out on the incident flight, just the a/p. It does mention it dropping out in previous similar events however. This was my point, with everything else going on the possible didn't realise thay had lost auththrust.

I note the Aviation Herald says the a/p dropped out followed by a/t

Paul
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Chris Trott
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Re: More on AF 447

Post by Chris Trott »

Don't use the WSJ article, use the actual BEA report, the WSJ article is full of BS that isn't talked about at all in the report.

http://www.bea.aero/fr/enquetes/vol.af. ... 011.en.pdf
At 2 h 08 min 07, the PNF said "you can maybe go a little to the left […]". The airplane began a
slight turn to the left, the change in relation to the initial route being about 12 degrees. The level
of turbulence increased slightly and the crew decided to reduce the speed to about Mach 0.8.

From 2 h 10 min 05, the autopilot then auto-thrust disengaged and the PF said "I have the
controls". The airplane began to roll to the right and the PF made a left nose-up input. 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).

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TobyV
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Re: More on AF 447

Post by TobyV »

That makes for rather sobering reading.

A few questions for the aviation professionals of the forum:

Looking at the times given, between the first comment made by a pilot that something is seriously wrong and the last comment after which point the situation was presumably hopeless, there seems to be an elapsed time of around 3.5 minutes. I appreciate that there are probably more useful actions that can be taken (i.e. to try to bring the aircraft back to a stable flight situation), but at what point in such a scenario might one expect a pilot to put out a "mayday" call? There seems to be no mention of any attempt to make any radio transmissions and of course, at the time, it was mentioned there were no radio transmissions other than the ACARS. I had always assumed this was because something was preventing them from doing so, but reading this I get the impression no attempt was made to do so *-)

Does making a comparison of what is given in this report with the ACARS messages (hopefully faithfully reproduced here: http://countjustonce.com/a330/af447-acars-1.png) shed any further light?

One stupid question from me, in these FBW aircraft where you only have a sidestick and throttles that are seemingly in no way mechanically connected to the flying surfaces and engines respectively, at what point, or under what circumstances can they cease to have any effect?

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Re: More on AF 447

Post by Chris Trott »

I'm not versed fully on overwarter comms procedures as we rarely had any flights at Air Tahoma which used HF (in fact only 2 aircraft were equipped with HF radios when I left), but there is a mention early on the report that they had been unable to reach Dakar on HF so it's possible they were in a spot where HF was not working and thus only a satellite phone call or ACARS (via satellite itself) would be the only way to make a broadcast. On our Convairs flying overwater, we had a sat phone onboard that had a button on the panel that could be pressed to transmit an emergency signal, but I don't know if that's available on their aircraft or not. I've not seen it on other transport-category aircraft equipped with a sat phone as part of the initial fit.

The thing I keep coming back to between the BEA report and the maintenance communications through the satellite is that the BEA report doesn't say anything about the condition of the PFD's beyond that they were displaying an IAS mismatch and loss of altitude and VS indications. Nothing on whether the Attitude Reference System was still operating and displaying properly. The fault messages reported suggest that at some point there were more faults than just the speed and altitude pitot and static ports because of the EFCS and ADIRU faults.

I think we're going to have a lot of unanswered questions until a fuller report becomes available this fall.

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VC10
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Re: More on AF 447

Post by VC10 »

TobyV wrote:One stupid question from me, in these FBW aircraft where you only have a sidestick and throttles that are seemingly in no way mechanically connected to the flying surfaces and engines respectively, at what point, or under what circumstances can they cease to have any effect?
Hi Toby,

No such thing as a stupid question

They stop working when they loose electrical power &/or in the case of Flt Ctrls, hyd power. The Engine EEC's are dual channel and have dual power supplies and all the flying control servo's are controlled by at least two computers and have dual hyd power sources.


With regard to radio messages there is the old aviation adage - aviate, navigate, communicate. I sometimes have to talk to a/c on HF and is not easy to understand what is being said in calm circumstances let alone in a storm. SATCOM is the clearest comms but I expect they were more interested in recovering the aircraft

Unfortunately the ACARS msg isn't too much help without the Central Maintenance Computer (CMC) data. The pilot sees the 'headline' info, the CMC will tell you which computers have generated the pilot's warning message. For example there are a possible 8 faults that can generate the F/CTL ALTN LAW message. If there is a fault that does not have an effect on Flt operations the pilot will not see a message, but it will be generated on the Post Flight Report that the engineers see

Paul
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Re: More on AF 447

Post by nigelb »

BEA has issued a statement regarding speculation on the AF447 crash:

http://airinsight.com/2011/05/27/bea-pu ... 447-crash/

This article has a link at the end to the full BEA statement in English (.pdf file) Other links include a podcast from an A330 type rating instructor discussing the BEA AF447 information and a 3 minute interview with two former NTSB investigators discussing the accident. Both those links are near the top of the article.

Nigel²

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Re: More on AF 447

Post by forthbridge »

I couldnt even begin to understand the ACARS messages, but overall a tragic event. Looking at it PURELY on what is reported a couple of things stand out: Pilot 'pulling up' - and the engines in idle toward the end of the flight, while they knew they were losing altitude rapidly.

If they went into some diabolical weather, then it's easy to imagine how quickly disorientation kicked in, and the crew appear to have been 'quick and responsive' - just that their actions were not (apparently) correct :(
Jim
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Re: More on AF 447

Post by Dev One »

Reading the latest BEA update it raises lots of questions, especially not knowing the aircraft intimately enough to know what type of sensor is used for the AOA & whether it is duplicated - it sounds as if that froze too & how does the active computer know which is the most valid input? Cross referencing to Attitude input?
I note that the Pilot (PF) did input nose down at 2:10:16.
Why did the THS go to full nose up? Did the computer think it was in Take-off mode?
Are the PFD & ISIS using the same sensors?
How independant are the inputs to the Hydraulic PFUs.
Remember we only have knowledge of one half of the system - the other half is not recorded.
Major lightening strike could also have played a part.....
I raise these questions ( & more) because I was on the fringes of developing a computerised Ground Control Station for Jindivik, & also in learning XML code for Sim models, one knows how easy it is to have a big reaction from a little difference or mistake in the coding!
I hope that the ones coding the software find the glitch.
Keith

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Re: More on AF 447

Post by Dev One »

Idly doing a bit of Googling I found this Technical Notes document - it might not be 100% applicable to 447, but it gave me an insight into not only needing to be a pilot, but to be a systems (computer & software) engineer.....Its very interesting - it still doesn't answer all my questions as it will take a long time to digest these notes....
Go to: www.hursts.eclipse.co.uk/airbus-technical/notes.pdf

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Re: More on AF 447

Post by Chris Trott »

nigelb wrote:BEA has issued a statement regarding speculation on the AF447 crash:

http://airinsight.com/2011/05/27/bea-pu ... 447-crash/

This article has a link at the end to the full BEA statement in English (.pdf file) Other links include a podcast from an A330 type rating instructor discussing the BEA AF447 information and a 3 minute interview with two former NTSB investigators discussing the accident. Both those links are near the top of the article.

Nigel²
Nigel, thanks for the podcasts, but I'm still not sure it sheds any real new light on the situation.

One note for others - the A330 has 3 pitot-static systems onboard. All are fully independent. However, all 3 use the exact same equipment. The problem that the A330 and A340 have encountered is that the original pitot probe design used on all systems is incapable of dealing with the levels of icing required to be dealt with under the aircraft's airworthiness certification. How this wasn't caught during testing is the focus of a serious FAA investigation (as the FAA certified the aircraft on the basis of the EASA certification) that is ongoing, but they've not recommended 2 different versions to be used, although one of those has since proven to be unacceptable as well, leaving only one probe type to be acceptable. The issue is with the placement more than anything, it's not the probes themselves as they are used on other aircraft without problems, but it's very difficult to change the placement of a probe after the aircraft is in service, especially in the numbers of the A330 and A340.

Basically, what happened here is that they entered weather that everyone else had routed around and the icing in the weather was so severe it overcame the anti-icing systems. The trick here is to find out whether that icing included the flight surfaces as well or just the pitot heads. Add to that the full explanation of what the PFD and ISIS were showing at the time and we'll have a better idea of what really happened. But in the end, I think it'll come down to the crew inadvertently entering extreme icing conditions at night for whatever reason (failure of radar or improper setting of radar) and then the aircraft failed due to that. The long-term thing is going to then be whether the aircraft should have been able to handle that situation and then whether the crew responded properly based on what they saw. From there, we'll see what changes occur.

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