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Joined: Thu May 17, 2001 12:02 pm

What Powers The Cabin Lights, Etc When...

Wed Aug 07, 2002 11:58 am

Hey guys.... just wondering..
I was on a night flight not too long ago, and I got a cockpit visit after the flight (an A320) and the flightdeck was cold, dark, and all shut down by the time that I got up there, and I was wondering, with all of the systems off, like the battery, APU etc. for the night, what powers the cabin lights, lavs, etc. after all of that is off? Is it the ground power? Also, when the last pax. leaves and the crew is putting the aircraft to bed, what is the process that they go thru to get all of these things turned off?

Posts: 122
Joined: Sat Feb 16, 2002 11:46 am

RE: What Powers The Cabin Lights, Etc When...

Wed Aug 07, 2002 12:08 pm

Ground power is usually plugged in before the APU is shut down. Many airlines have gone to plugging in to ground power before the engines are shut down to save on cycles on the APU and gas. When you are done for the night the lights in the cabin are all turned off from the flight attendant station. The ground power can be shut down when the aircraft is unattended.
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Joined: Mon Nov 01, 1999 4:34 pm

RE: What Powers The Cabin Lights, Etc When...

Thu Aug 08, 2002 2:39 pm

Ground handlers usually turn off most things, lights etc.

they are the last people to use the aeroplane (cleaning etc)

Just go into the cockpit turn off the GPU switch and let the old girl sleep!
lmml 14/32
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Joined: Tue Jan 30, 2001 2:27 am

RE: What Powers The Cabin Lights, Etc When...

Fri Aug 09, 2002 12:27 am

If by dark you mean the screens it is because the crew have deliberately dimmed them. This extends the life of the tube, I am told. If the cabin lights were still on it means that the aircraft was still powered by the APU or Ground Power. If none of these was on the battery kicks in and the emergency lights go on. On the 320 this provides a lot of light.
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Joined: Tue Jan 01, 2002 5:38 am

RE: What Powers The Cabin Lights, Etc When...

Fri Aug 09, 2002 1:42 am

When the cockpit is dark and the cabin lights are on it means the Ground Service Bus is powering the lights and electrical outlets for the cleaners. This is virtually always powered by the external power system.
There's a switch, normally on the Forward Flight Attendants' panel, to turn this system on. It allows the cleaners to do their jobs without powering (thus reducing the useful life of) the entire avionics suite in the aircraft. Boeing is starting to put the Ground Service Bus switch in the cockpit on some of their aircraft.

The emergency lights have their own battery packs located throughout the aircraft (placement is a function of the manufacturer and customer) and they are mounted on their own integral battery charger bases. If power is on the aircraft and subsequently lost (while the Emergency lights are armed through the cockpit switch) the lights automatically come on and stay on until manually turned off or the batteries die. Depending on the aircraft they are good for 15 to 90 minutes. Some aircraft have an emergency light "test" switch on one or more Flight Attendants' panels so that you don't have to go to the cockpit to test the system or turn on the lights.
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
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Joined: Mon Apr 08, 2002 1:14 am

RE: What Powers The Cabin Lights, Etc When...

Fri Aug 09, 2002 10:49 am

Emergency battery pack location is also determined by FAR 25.812 which states that in the event of a single vertical separation of the fuselage during a crash (at any location), no more than 25% of the lights are rendered inoperative, in addition to those directly damaged by the separation.

Also, each emergency exit sign must remain operative and at least one exterior emergency light for each side of the airplane remains operative exclusive of those that are directly damaged by the separation.

You know how I like attention to detail Avioinker.......


RE: What Powers The Cabin Lights, Etc When...

Fri Aug 09, 2002 1:40 pm

Dear Concorde1518 -
The electrical systems of airplanes are "split" in various separate "busses", and many airplanes have something that may bea "cabin service bus" which powers various cabin lights, and electrical outlets which permit the cleaning staff to connect vacuum cleaners. Generally an airplane will not be left "abandoned" with an APU powering the aircraft, without having crew or ground engineers present around the aircraft. Expect an "external power unit" to power the aircraft for the cabin cleaning...
(s) Skipper

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