Avionics bay fire suppression?

[Uplinker]

Do Boeing aircraft have avionics bay fire extinguishers? Airbus 330/321/320 don't (they do have extinguishers in the cargo holds, and we can route avionics smoke and fumes overboard). I am just wondering about an avionics fire in mid ocean. We can detect smoke and the standard drill is to vent smoke overboard, go to emergency electrical config, descend and land (amongst other things) - but obviously over the ocean that would be a ditching. However, we do not have any actual extinguishers in the avionics bay, apart from a handheld BCF in the 330’s.

I have just learnt that MH370 was carrying lithium ion batteries in the hold? If that were true and they were in the forward cargo bay, could they have burned through the wall to the avionics bay possibly causing the symptoms that were reported - transponder and ACARS going off line etc., no further radio contact etc.?

Apologies if this has been discussed, I did do a search but did not see anything on this specific subject.

[Winnerhofer]

The last minutes of Swissair Flight 111 : Stephen Kimber (http://stephenkimber.com/books/previous-books/the-last-minutes-of-swissair-flight-111)

[vilas]

I do not think extinguisher can achieve anything in avionics bay unless the short circuit can be taken care of and that is what the drill aims at.Their is no other inflammable material there while in cargo hold you can have anything.

[Uplinker]

I beg to differ, Vilas. electronic circuits can, and do burn.

[grounded27]

It is not likely that we will see fire suppression in the avionics bay any time soon, first priority in cooling avionics is fuel for a fire.. Mass quantity's of air. Much more necessary than fire protection. There are extreme lengths that a manufacturer would have to go through, an inert gas or liquid cooling system for example that contained in an airtight chamber - highly fire resistant chamber.....Not likely.

[Andy_P]

It is not likely that we will see fire suppression in the avionics bay any time soon, first priority in cooling avionics is fuel for a fire.. Mass quantity's of air. Much more necessary than fire protection. There are extreme lengths that a manufacturer would have to go through, an inert gas or liquid cooling system for example that contained in an airtight chamber - highly fire resistant chamber.....Not likely.

No different to a server room that is used to run web sites like this. They need cooling and have fire suppression systems designed to preserve the electronics.

Biggest difference I can see, is that a server room would have an escape route, not so in an aircraft, so you would want to be pretty dam sure that the avionics bay had a very tight seal from the rest of the cabin!

[Uplinker]

I can foresee difficulties, as Andy says, such as the need to seal the avionics bay first by shutting all the air valves to prevent the halon being dumped straight overboard or into the flight deck, but we have extinguishers for the hold baggage, why not the avionics bay?

What is the rational for having no extinguishers in an area packed with electrical equipment, including the aircraft batteries?

[vilas]

Uplinker
Electronic circuits may burn but if the supply is cut off the fire cannot go on. Lack of fire suppression in all aircrafts cannot be surely by accident.

[Uplinker]

Well this is my point and question really, vilas. Electronic circuits can emit what we in the business* used to call "loud brown smells", when a component has failed, is getting too hot, breaking down and emiting fumes, but which stop when you remove the power. However, if the insulation, resin, or plastic parts on a circuit board have caught fire and are burning, (ie flames are present), then simply turning off the electricity supply is not going to stop that.

Or are you saying that any and all parts of all aircraft avionics and avionics bays are constructed from non-flammable materials? I don't know if they are or not.

I've practised avionics smoke and fumes removal many times in the SIM, but the thought of actual avionics fire and the lack of remotely operated extinguishers in the avionics bay has only just occurred to me. Airbus A330 has a BCF in there, but one of us would have to climb down in there with smoke hood on etc., and there is nothing about tackling an avionics fire in the QRH, except a vague statement:

"IF SMOKE SOURCE IMMEDIATELY OBVIOUS, ACCESSIBLE AND EXTINGUISHABLE:
FAULTY EQPT.............................................ISOLATE".

We have certainly never been trained to go down there in flight.



* I was an electronics engineer in a previous life.

[vilas]

Well nothing wrong in thinking about it but after Swiss MD11 this subject has been given lot of thought and even the focus of smoke procedure has changed. Your question can only be answered by the manufacturer.