Re. Avrflr post 330.
Avrflr,
“We'll call that miracle number 1 “
“Miracle” is not standard systems safety analysis terminology. Please define. Here are some of the terms we use in the industry by way of example. Personally though, I prefer to stick to numbers for clarity.
Remote: < 1E-5 failure events per flying hour
Extremely remote < 1E-7 “
Extremely improbable < 1E-9 “
Are “centre tank pump1, 2 running normally” recorded FDR parameters?
Are the centre tank push-buttons positions recorded?
Would failure of the CT pump pressure sensors be recorded?
Note that some things can’t be recorded as they are not signalled e.g. jet-pump induced water scavenge flow.
Can anyone out there help with an applicable list of FDR parameters?
While I'm asking, can anyone help with a schematic?
“So, miracle number 2 is that the last drop of water passes through the injectors on both engines at the precise moment that the engines hit the ground? Come on.”
That’s not what I said. So, what I did say is very unlikely. The accident was unlikely too. It had unlikely causes. Dismissing possibilities on the grounds that they are unlikely is not helpful. I’ve never noticed blinkers in the kit of any of the air accident investigators that I’ve met.
The key to this accident is that there was a common-mode failure. The same thing happened to both engines at the same time. One common failure mode could originate from the engine control system/software. This has been ruled out by the AAIB. The engines themselves also got a posthumous clean bill of health. Another source of a common-mode failure might be the fuel quality. The AAIB have found no fault with it. Likewise temperature: the aircraft was operating within its environmental design envelope.
As far as systems common-mode failure sources are concerned, the only possibility that has occurred to me so far is that the fuel feed system allows both engines to be fed simultaneously from the same (centre) tank. If anyone can think of any others, please post them.
Last edited by SyEng; 23rd Feb 2008 at 15:56.
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