View Full Version : Loss of power on ground after chocks on

28th May 2018, 07:13
Hi there,

While this is rare to experience, what will happen if there is no power (APU INOP and no ground power) to the aircraft? Will there be standby power for cabin lighting and the basic essential electrical needs for the aircraft? What's the duration? Not much is mentioned in FCOM 2.


28th May 2018, 08:24
I believe not much lighting left. If you look on the QRH for Emergency Elec config, there is a table showing the system remaining on battery only.
It happened to me to shut down the engines before the APU was available. cockpit went dark and very quiet for about 10/15 seconds until APU took over. Not a big deal in that case.
If you have already prepared the FMS, the data will still be there. One important thing in case you lose APU generator or EPU is to switch off the ADIRS. There is an external horn that will trigger until the ADIRS are switched off. The reason is that on battery only you just have partial avionic ventilation system working and the ADIRS system can overheat.

28th May 2018, 23:00
Which aircraft are we talking about?

Regarding the cabin. The Standby Busses and Battery Busses should power passenger address for announcements. The emergency lights should activate in the cabin (using their own battery power supplies). If you don't wish to flatten the emergency light batteries, switch them off (assuming there is enough light in the cabin for proper visibility). If power loss occurs just before a flight, note the time that the emergency lights have been in use. Our manuals state that the batteries must have been recharging for a certain amount of time before flight.

29th May 2018, 01:46
Usually everything(really just most things) goes dark, emergency lights come on. You are on battery power with it slowly depleting. PA probably still works so you could say a few calming words to the pax if you have pax on board. With these major airline opeations, it seems that most pilots don't get to see what it is like when just on battery power. Depending on type and systems, expect a delay if this happens just before pushback. I had someone screw up a switchover from ground power to aircraft power recently and it resulted in several strange false warnings that took more than half an hour for maintenance to solve. Had to do a complete power shutdown with all the test warnings during power up to fix it.

As for the ADIRS switch, that would be specific to the 777(maybe some others as well) with the ADIRU switch.