Power failure?

[2MilesHigh]

I've been reading about lightning strikes and such here; does this kind of thing ever result in losing power? What happens on an airliner (757,767, etc) when electrical power is lost? Obviously there are backups, but what does a pilot go through?

[carbonfibre]

2 mile high

I am not an airline pilot, (yet) , but can summarise from studies what they have as backup.

I assume your talking about the electrical sytems, EFIS and the like, which are run from the generators off the engines, but they could also use the APU (auxillary power unit) which is in the tail of the aircraft in flight for emergencies

If all that fails they have emergency battery back up for the essentail flying devices and an air driven hydraulic pump which can be dropped from the belly of an aircraft, its called the RAT , (ram air turbine), i know the 767 has then but not sure what other aircraft do

Hope this helps

:cool: :rolleyes:

[Sheep Guts]

Just an aside. Not really answering your question,but a few years back....

A RFDS (Royal Flying Doctors Service) PC-12 single engine Turbine, PT6 powered, suffered a lightning strike outside Alice Springs in Australia. It returned safely to base with partial power. The Engine was a right-off though. I dont know if there was a ASTB report on it, but it would be interesting too see what happened inside th engine R.E. the failure.

It in itself proves that when dealing with forces of nature lightning is unpredictable and the damage it can cause undefinable. So what systems or engine problems that could occur is unknown you just hope that all the bonding straps and earth shunt etc are serviceable. That is all Aircraft Types. When you dealing with Millions of volts causing huge potential differences damage come sin all forms.

Iknow a PC-12 is far from a Commercial Airliner, but they do have basic EFIS and FMC systems on board.

Food for thought

Regards
Sheep

[Tinstaafl]

One of our a/c got hit by lightning late last year.

The damage consisted of small entry & exit holes on the wing tip & tailplane + the whole a/c needed degaussing before our engineers could get the compasses swung to within tolerances.

[TheShadow]

2MilesHigh

Here is an example (http://www.iasa.com.au/folders/Safety_Issues/FAA_Inaction/727elecfail33yearsago.html) of what you're querying. It's an accident that happened 34 years ago.

Per the Swissair Flight 111 accident of Sep 98, however, certain types of wiring can dry or wet arc-track and take out whole wiring bundles at a time (obviously causing a multiplicity of unrelated systems failures). Because of the very high temperatures generated by an arc-tracking event, a wire-bundle crossing an oxygen line can cause a pinhole to be burnt into it creating an oxy blow-torch. There has been much surmise that the fan-shaped pattern found in the crown areas of MD-11 HB-IWF was caused by just such an event. The wiring insulation type that can both wet and dry arc-track is the aromatic polyimides (aka/by their generic name of Kapton).

In the SR-111 accident it was found that the L1 and R1 front pax doors had chafing of wiring where the doors recessed into the ceiling. Lengths of wiring associated with the IFEN system were found showing evidence of arc-tracking. After that accident many electrical AD's were introduced. One addressed the vulnerability of the Standby Flight Instruments during bus-failure conditions.

The Final Report of that accident will be released by the TSB in the third week of March. One of the conclusions may be that wiring itself has no "reliable redundancy". In addition, lengthy trouble-shooting checklists for smoke of unknown origin are likely to be found to be a root cause for electrical fires getting out of control (simply because they allow the power to remain on the wiring). The arrangement on the MD-11 for switching manually between busses and generators is called the Smoke/Elec/Air Switch. It kills power to a set of generators and their associated busses - but then reintroduces it as you go on to the next selection. That is like pushing a Circuit Breaker back in on a failed circuit. That is significant because normal CB's will probably not trip during an arc-tracking event. And that is why much effort is being put into developing AFCI's (hybrid CB's called arc-fault circuit interrupters (http://www.aviationtoday.com/reports/avionics/previous/0201/0201safety.htm)). But don't expect to see those anytime soon.

[jtr]

Have been struck a few times in A340's and 330's. Scares the crap out of you, but no immediate effects.

Can usually find the entry and exit points if you look hard enough.

[QAVION]

"And that is why much effort is being put into developing AFCI's (hybrid CB's called arc-fault circuit interrupters). But don't expect to see those anytime soon."

Sounds much like what was recently fitted to one of our 747-400's (on an trial/experimental basis). They are currently operating in tandem with some of the regular CB's. We are requested to check them on every transit until told otherwise.

Regards.
Q.

[2MilesHigh]

Do these systems (the RAT, etc.) kick in automatically, or does the flight crew switch power sources manually? Or is it different from a/c to a/c?