Can any ex-Nimrod FEs answer this?

[Shaggy Sheep Driver]

Is it possible to get external electrical power onto the aeroplane when the two aircraft batteries are flat? We have an invertor powering our (obviously now grounded) MR2, but the procedure calls for battery power to be available before ground power will power the aircraft; no batteries, no power to the aeroplane.

This seems intuitivly to be wrong. Surely the aeroplane wasn't rendered unusable when it was in service if the batteries are inadvertantly allowed to get discharged? Is there a way to apply ground power without battery power being available, and then allow ground power to charge the batteries in the normal way?

Also, if the batteries are disconnected while ground power is powering the aeroplane, ground power is dropped and the electrics die. Did this happen with generator-supplied power as well? Would a Nimrod in flight, powered by the engine-driven generators, be rendered devoid of all electrical power despite it being available from the generators if the batteries failed?

CROSS POSTED ON MIL FORUM AS WELL - responses are there, now, so please ignore this thread and post on MIL instead.

[rigpiggy]

Most aircraft that allow charging from GPU require a minimum voltage to avoid thermal runaway on the batteries. As such you must have power to close the battery relay.

A cheat that has worked in the past is to have the aircraft configured fully ie gpu switched on/powered up, prior to turning on the battery. the surface voltage sometimes will have enough oomph to trip the relay. At that time it should hold the relay open with ground power.

[kevnurse]

check my answer on the mil forum

[Shaggy Sheep Driver]

Thanks Kev.

This is being discussed on Mil forum, so please post there rather than here from now on for this thread.

Thanks

Shaggy.