Fires in avionics bays

[tubby linton]

What are the certification requirements for a fire in an avionic bay? My airbus has a smoke detector fitted in the bay but no automatic fire extinguishing . The bay is accessible in flight but realistically how long will the bay and the equipment it contains survive if the bay is not accessed and the fire continues?

[NSEU]

Apart from dust and batteries, are there really a lot of flammable things in equipment bays? Most things in there should either be either heat or flame resistant. No wood, paper, fabric, etc.

Metal racks, metal boxes, fire-retardant insulation blankets, hopefully non-Kapton wiring, a few small plastic items, ....

Of course, then there are the oxygen bottles on some aircraft types, but hopefully the O2 will vent overboard if the heat causes the O2 pressure to rise.

[noughtsnones]

One possible requirement cascade starts with FAA § 23.1309 "Equipment, systems, and installations" or its EASA equivalent; the acceptable means of compliance are usually by the adoption of a range of organisation, design and verification techniques...

The normal thermal, overheat, fire and explosion proof requirements are determined by the system integrator according to design assessment; these are the domain of standards including ARP 4761 and ARP 4754.

The resultant hardware parts specifications will include environmental test requirements; usually by the system integrator referencing selected parts of RTCA DO-160 / ED-14.

As your query context "avionics bay" and as NSEU has observed the system integrator has taken significant measures to remove combustion sustaining and explosion risk materials e.g. by the absence of fuels and hydraulic oils, even though a source of ignition is present.

My speculation is therefore that there are thermal requirements on all avionics bay electronics: -
including local assembly normal operation temperatures,
including adverse temperatures e.g. due to heat release when a local power supply "shorts",
excluding fire resistance for long duration,
excluding explosion proofness.

[grounded27]

I can only think of Swissair Flight 111. Still unknown. None the less if there was a major electrical short there is no fire agent that would help. Adding the fact that electronics require cooling via air flow there is no current logical answer other than the most sutable airport to land at. The only thing mechanially we can do is monitor current flow "we have circuit breakers".

I always thought it strange by Airbus to place the sniffer on the F/O side..

Hell, if it smells like **** it most likely is. Deal with the flight deck effect.

[compressor stall]

As an aside, the reason that Airbus have the smoke checklist in order of 1. AIRCON. 2. CABIN EQIP. 3.AVIONICS is because historically they are the most likely causes for fire detections.