Ques regarding Emergency Electrical config

[WhySoTough]

Just reading through airbus systems and apologies for sounding stupid as this is very new to me.
When in electric emergency configuration, you've basically lost both your AS BUSes, and now have 22 minutes of battery left.
I read the procedure is that when above 100 knots (which you should be), the RAT will extend automatically, and AC ESS bus is fed by the static invertoer.

Firstly, why not use APU generator? =/

Second, with the RAT, what are you limited to now?

Any extra information is appreciated.

Thanks!

[Dan Winterland]

Airbus recommend that an APU start isn't attempted, because if it isn't successful then your batteries will be flat and you will be completely out of options.

The RAT runs the emergency generator through the Blue hydraullic system. The services available ar on a table in the QRH. You can keep flying safely in the Emergency Electrical Failure configuration until your fuel runs out, even though you will have a LAND ASAP red notification.

[Cough]

Dan,

We have a split fleet, our older models don't recommend that the APU is started, however, in the newer ones 'consideration should be given to starting the APU'.

Depends on the serial number and configuration - Check the FCTM/FCOM's as appropriate...