Fuel pumps in EMER ELEC CONFIG

[JerryW58]

Hi all,

I was doing some reading about the EMER ELEC config and couldn't find an explanation for the following:

Edit: Probably worth mentioning that this applies to the A320 family.

Looking at the FCOM-PRO-ABN section
The ECAM tells us that when we are in emer elec config, we are feeding the engines on gravity only, confirmed by the status page which states that the fuel pumps are INOP.

Looking at the QRH-Sys remaining section
It looks like this section is confirming what's in the FCOM/ on ECAM, since the fuel pumps are not mentioned in list of systems remaining.

Looking at the FCOM-DSC-Fuel section
If I understand the electrical supply table well, the inner tank pumps are normally being supplied by AC1 and by DC ESS bus when in EMER ELEC. This suggests that there would still be one pump in each tank supplying positive fuel pressure to the engine whilst in EMER ELEC config.

Can any of you wise men clarify this? Are the pumps shed because of the load on the EMER GEN? I'm probably missing something..

Also, would it be possible to switch the GEN 1 LINE OFF while in EMER ELEC CONFIG to connect the inner tank pumps to GEN 1? (In case EMER ELEC CONFIG was caused by a failure of AC BUS 1+2 ISO the Generators)

Thanks!

[Fursty Ferret]

I think - though willing to be proved wrong - that you do indeed lose the fuel pumps in elec emergency configuration.

They're shown as operative in the FCOM because you can be in EEC and still have them, if you've put the aircraft into the smoke configuration. In this case, the relays remain energised on the DC ESS bus and the pumps are powered directly from their onside generator. In true EEC with both generators unavailable, the pumps have no power supply but the relays are still powered.

It's not a brilliant description.

Also, would it be possible to switch the GEN 1 LINE OFF while in EMER ELEC CONFIG to connect the inner tank pumps to GEN 1? (In case EMER ELEC CONFIG was caused by a failure of AC BUS 1+2 ISO the Generators)

Probably. But why would you want to?

[JerryW58]

Thanks Fursty,

Good point. Although I can't see the FCOM distuingishing relais and pumps, I think you raise a good point in saying that the pumps run on AC power and therefore, the relais must be powered by the DC ESS.

Probably. But why would you want to?

If it would work, connecting the inner tank pumps to GEN 1 would imho reduce the initial workload and gives one less thing to worry about (GRVT feeding procedure and avoiding negative G's).