Saturday, 13 July 2013

Boeing Engineers buy Management hats.

It hasn't been a good year for Boeing. In the early part of the year their band spanking new 787 Dreamliner was grounded because of several battery problems, some of which resulted in fires. After 4 months of trying work by Boeing the 787 was declared airworthy when several fixes were made. Primarily fitting the batteries in a large semi armoured box and increasing the spacing between batteries to allow more cooling. The root cause of the problem was never identified, everything that looked dodgy was fixed but with no definitive proof.
Boeing rolled out the fix to the entire fleet start with Ethiopian Airlines aircraft in May, hoping this was the end of the story but come the 12 July and another fire is reported on a 787 parked at Heathrow, this aircraft had been parked up for several hours and the fire was detected by a smoke detector in the cabin.. This time doesn't look like the batteries, as the fire is in a different place, just in front of the fin.
The few schematics of the aircraft, that I have seen, give this as the location of an electrical power distribution hub, which I suspect should have been largely idle at the time simply providing power for lighting, air conditioning and perhaps so cleaning appliances. The source of the power was most likely a ground feed with no power coming from the batteries and the APU switched off.
This doesn't totally isolate it from the batteries as they are essentially part of the same system which leads to the possibility that will be familiar to most programmers, that when you fix one problem another one shows up or you discover that despite find a problem in one place the problem persists because it was occurring earlier on in the chain but only becomes apparent.
In this case if we imagine that the batteries are overheating because their current flow exceeds the specifications. If the batteries are then uprated to take this flow, then there will still be excess current flowing around the system which will produce heat and if there are any vulnerable parts they may fail.
I don't know whether the batteries were being charged or discharged at the time of the fires or if they were in any other mode at the time, but several do appear to have happened on the ground, with the reduced air flow, this would produce overheating compared with when flying, this would also apply to this location in the aircraft.
In some some forms of battery backed power supply all input power is directed via the battery system so that if the external power fails there is a smooth transition to using the batteries. If this is the case with the 787's system then it would mean that the power reaching the power distribution points would have gone through the battery system.
If this is a completely separate fault then perhaps the problem has been fixed but it is still a problem that Boeing could not pin down the fault, it is an unsatisfactory state of affairs as you cannot say you have fixed something you did not identify, at the very least Boeing should be continuing to investigate the original problem, until they can categorically explain what it is and demonstrate the fix works and that they now understand the system.
After the 1986 Challenger disaster it became clear that some of the Morton Thiokol engineers had been asked to make decisions with their "management hats on", rather than their engineering knowledge, Boeing looks to be doing the same. If there was a professional body for Engineers this should result in some being kicked out. The point of being a professional is that you but the ethics before company and self. We have been here before it it usually doesn't end untill people die.

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