In the pre-broadcast publicity for tomorrow's Nova episode (see my other post
), I can't help but notice rather generic references to aircraft wiring.
To clarify, the TSB's report is not particularly critical of aircraft wiring in general. It is however, specifically critical of the wiring practices involved in the installation of Swissair 111's inflight entertainment system (IFEN). Yes, any wire can arc, and it is an incredibly bad idea to construct aircraft using flammable materials that may be ignited by a relatively small electrical arc. And to do fully aware of the problem is unforgivable, but ...
In Section 2.21 (Fire Initiation) the TSB's report states:
Because the IFEN wires in the STA 383 area were routed separately and not along existing wire bundles, it is less likely that the IFEN wires could be in contact with aircraft wires within the localized area where the fire most likely started; therefore, the more likely candidate wires for this type of scenario would be the other wires in the bundle of four IFEN PSU cables and the 16 AWG control wire.
In other words, we know that two wires were involved in the event that started the fire. We know that one of the wires involved part of the IFEN system. And it is more likely than not that the other was as well.
Also from the TSB's report:
18.104.22.168 IFEN Integration ï¿½ Electrical Power Supply
In the configuration that was certified, the IFEN was connected to aircraft power in a way that was incompatible with the MD-11 emergency electrical load-shedding design philosophy and was not compliant with the type certificate of the aircraft.
3.2 Findings as to Risk
The Federal Aviation Administration (FAA) STC approval process for the IFEN did not ensure that the designated alteration station (DAS) employed personnel with sufficient aircraft-specific knowledge to appropriately assess the integration of the IFEN power supply with aircraft power before granting certification.
The acronym "IFEN" occurs 243 times in the TSB's final report. The word "wiring" occurs 95 times.