In-Flight Fires Wreak Havoc With Systems Reliability

Air Safety Week, Sept 22, 2003

"Safety concerns are for a video unit fire/smolder to cause this many collateral issues is not good. Because this unit did not draw more power, the CBs did not pop, and perhaps a thermal shutdown feature would be appropriate for aviation video systems."

Issue: Perhaps not really understanding the mechanics of arcing? Arcing involves the carbonization of some types of wire insulation and, carbon being conductive, the charring provides an alternate path for an electric current. The conductor may not draw sufficient current to thermally trip the breaker, yet the whole wiring bundle may still burn (particularly if it has a vertical orientation). With insulation thus destroyed, conductors may touch and fuse together. If the damage progresses that far, CBs will trip by shorting out.

Language barrier

Case: B767 cargo fire warning.

Details: "On takeoff ... we received a momentary main cargo fire warning. This included an EICAS message, fire bell and fire lights at 80 knots on takeoff roll. This warning was extremely brief.

"Once airborne, we coordinated with our company dispatcher via ACARS [airborne communications addressing and reporting system] and the decision was made to divert to Tokyo [Narita] airport. We declared an emergency, dumped as much fuel as possible, and then made on overweight landing. After landing, the main cargo fire warning illuminated again, and remained on until the aircraft was shut down.

"Due to the language barriers of being in the Japan ATC system, communicating our abnormal situation was nearly impossible. It took over 6 transmissions to get them to understand that we were declaring an emergency and that we needed to land ASAP. Most importantly, once we landed, it was impossible to talk with the fire crews. We could not understand them, and they could not speak any English. Therefore, the situation became very hectic and chaotic. Not being able to communicate clearly with ATC or [ARFF] personnel would have made this a very dire situation, had we been on fire."

Issues:

* Erratic instruments.

* Language problem. Basic proficiency in routine messages for non-native English speakers does not mean the ability to communicate effectively in abnormal situations.

'A large blowtorch type flame erupted'

Case: B737-300 arcing at cockpit window heat connection.

Details: "While in cruise [on a functional check flight] and approximately one hour after turning on the window heat, I heard a loud cracking or popping noise behind me. I looked back to the CB panel and then turned around and noticed that the electrical terminal connector on my window [R1] ... produced a sparkler type firework.

"I immediately donned my oxygen mask and goggles and saw that the captain and mechanic jump seater had also done the same thing. Captain declared an emergency and commenced a descent and turn back to the coast.

"The cockpit door had remained open the entire flight since there were only three people on board. This probably helped to dissipate the smoke and fumes quicker.

"It is my belief if I had been 'heads down' typing on the FMC panel, the flame or sparks would have made contact with my head and hair. As it was, I had spots of black ash on my shirt and pants. Pilots who apply alcohol based hair sprays or gels should be made aware of the potential for fire and sparks igniting their hair.