b744 electrical
 

if external power, powesr the ground handling bus or main cargo handling bus when is just plugged to the a/c why selected ON? if it is already powering the bus?
thank you

Because it might be nice to power up the whole aircraft…

Simply put the aircraft is parked devoid of power.

You arrive, plug in power and now you can with the other ground crew.
Fuel the aircraft
Start cargo loading
Turn sufficient lights and power on to service / clean the interior.

No one has needed to enter the somewhat complex cockpit who’s unlicensed to operate it and it can safely remain dark until an engineer or flight deck crew arrive.

$$$

https://cimg4.ibsrv.net/gimg/pprune....cf2f87a16.jpeg

Hi all,

Adding to above post, main deck cargo handling is powered only from external power bus 2 (RH) or APU gen 2.