More on AF 447

[nigelb]

The details of the black box investigation.

http://online.wsj.com/article/SB1000142 ... TopStories

Nigel²

[VEGAS]

Cheers Nigel. I've been waiting for news on this ever since it happened.

This article is very interesting but something just does'nt add up with this accident.

All seems too easy to point the finger. Especially with a huge commercial reputation on the line.

[Chris Trott]

Having read the briefing, I think it leaves even more questions than it answers and the article ignores the briefing's contents.

The biggest problem is that it states the crew didn't increase the throttle, but the briefing states that the engines were put at maximum thrust at the first sign of airspeed decay and left there until something happened that made them think the plane was dangerously accelerating which caused them to pull the throttles to idle and trying to push the nose down. Comments by the crew also seems to indicate they thought the plane was recovering and leveling off or would be leveling off even though the plane was still stalled. I think whatever happened it was sudden and there were more problems with the onboard displays than the briefing lets on and that between that, the fact they were in Night IMC with no external references for the aircraft's attitude, and the rapid onset of the emergency caused the final outcome and there may not have been much the crew could have done once they entered the icing - which we need to know if they could have avoided as the initial suspicion by those in the area that night was that they had misconfigured their radar and did not see the extent of the convective activity, especially since the storms were not electrically active so at night would be extremely hard to see.

[jonesey2k]

Are we at the stage now where we are relying too much on high tech equipment and computers to sort everything out and them becoming lost when it doesn't?

[Chris Trott]

Personally I don't think so. The airplane and crew initially did what they were supposed to. The Autothrottle disconnected when the computers realized they weren't getting good information and the crew immediately switched to the "Alternate Control Laws" which removes all but the most basic of the computer's automatic functions from the loop, meaning that the computer couldn't incorrectly follow what it "saw" and try to make the plane do something it wasn't supposed to, which has happened in the past. From that point on, that A330 was no different than a Boeing 707. If the ice built up faster than it could be taken care of by the anti-icing systems and the instrumentation was unreliable due to port blockage, then you run into the same problem whether you've got computers or not - you can't see anything outside to orient yourself and you can't know what inside to trust. At high altitude that is a dangerous combination and it got the better of them.

[dodger]

Hi All,

Well i am not going to comment as for one thing i am not a pilot in the real world but as its 2yrs ago on Wednesday when it happened i think its really fantastic that the black boxes are in the condition they are for the time they were in the sea,

One thing i will say is the people in the film that was made last year trying to piece together the accident on the information they had at the time should be very proud of themselves as they were not far off the mark,

Roger.

[VC10]

the crew immediately switched to the "Alternate Control Laws" which removes all but the most basic of the computer's automatic functions from the loop,

The crew can't 'switch' to Alternate control laws, it is an automatic function depending on the nature of the failure.
Although the A346 is a little more refined the basics arethe same as the A330





With regard to engine power, the a/p may drop out but that does not necessarally mean the autothrust would. Possibly autothrust did drop out when an arming condition was lost, such as an ADIR faulting itself due to the icing. The crew may have though it was still engaged, controlling airspeed and because there is no visual feedback by the thrust levers moving the crew didn't realise they didn't have autothrust due to other distractions on the FD.


Paul

[Chris Trott]

Paul, the briefing specifically states that autothrust disengages, not the autopilot. The autopilot is deselected after autothrust drops out.

As for selecting Alternate Control, in the A32X series, you can force the Alternate laws by pulling certain circuit breakers (this is what was done as part of the emergency checklists in the USAir Hudson River accident), is this not also possible with the A330 and A340? The way the report reads, although incomplete, seems to indicate the PF gave an instruction "Alternate Law" and not a confirmation of it being displayed to them, which would support that they were either ensuring that Alternate Law had been activated or that the PNF was to perform the procedure to activate it.

[VC10]

Hi Chris,

Thanks for the clarification, I must have misread the report.

There are no CB's on the Flt Dk of 330/340's just soft reset 'CB's' for specific Computers (SDAC, Pack Controllers, CIDS. FWC's, LGCIU's, FMGEC's etc). Flt ctrl computers can only be isolated, not depowered, by switching off the relevent computer on the o/hd panel. I can't see a Flt Ctrl Computer being turned off until a computer fault is annunciated.

Paul

[WhisperJet]

Follow the story here for more details...

http://www.avherald.com/h?article=41a81ef1/0068&opt=0

Best,

Nick