Airliner Wiring Flaws -3 (Out of Sight and Out of Mind)

Page Three

Poorly spaced wire-bundles - You could lose the lot. There is no redundancy.

Still feeling as keen on FBW (Fly By Wire Flight Controls)?

You may luck out and the electrical arc-fire may not be propagated by adjacent flammable materials. If it affects adjacent wiring bundles, they can also arc. If there is oxygen tubing in the vicinity just remember that the melting point of stainless steel is way below the temperature that an arc can reach.

The penetration of HP oxygen stainless steel tubing is only to a pinhole stage -as the arc will be cooled and deflected as soon as a pinhole allows the oxygen to escape in blowtorch fashion. Wonder what those fan-shaped patterns in the ceiling of Swissair Flt 111 were caused by?

read about this incident here

If this cargo hold fire had happened earlier, for a number of reasons they may not have made it.

a. They got the warning at only 10 miles on approach.

b. On touchdown the power is removed from the heater circuit that had shorted out and

c. The 2nd & 3rd bottles fire their whole charge on touchdown

Otherwise the 2nd and 3rd bottles are simply eked out by metering a 3% concentration of Halon over 195 minutes (suppression mode).

I wonder what would have happened once the hull had burnt through? Would that 3% concentration have been maintained - or would the fire have been stoked by the inflow of air?

There are other anomalies apparent in this cargo-hold smoke/fire system also. Go to the URL above for the details.

There are different wiring malfunctions - shorts, dry and wet arc-tracking and ticking faults. There are also "intermittencies".

It has been proven that visual inspection of wiring is ineffectual in finding wiring faults - and can in fact lead to more faults. So intrusive inspection isn't normally carried out (not that you can access more than about 60% of an aircraft's wiring anyway). The wiring is hidden away and secreted in wing trailing edges and other inaccessible areas. The best solution is a wiring installation that's planned to avoid failure and ease inspection.