B737 Fuel Pumps Dc Current Control

[LEM]

Each Fuel Pump is Ac powered and DC controlled.

For example, the left aft main pump is powered by TFR bus1, and controlled by DC Bus1.

If the DC Bus1 was failed (like in the case where TR1 is failed and you capture the Glideslope... , is the pump going to "stay in the last position", or is it going to fail?

[alexban]

Hi LEM
Are you sure about this 'DC controlled"?
All I can found about the pumps is that the pupms are AC powered and fuel cooled and lubricated.
Not even in the AMM ,maintainance manual, did I find something regarding the DC controlled thing.
I'll check back on your question,maybe there is some CB to test on ground your question.

[Jet II]

If DC Bus 1 is failed you would lose the feed to the P5-2 Fuel System Module and thereby lose the 28 VDC feed to the R18 Tank 1 Aft Boost Pump Relay - result the contacts would open and the AC feed to the Boost Pump would stop.

Wiring Diagram Manual chapter 28-23-01 page 1

Hope thats clear

[LEM]

Yes, that surprised me a little, too, as I'm going through Pat Boone's Management Reference Guide (which WAS free to download till recently)...

Apparently, the controller for the aft pump is DC Bus 1 (and 2 for the right one), and 2 and 1 for the fwd pumps...

This is confirmed by Jet II...

You never stop learning

[LEM]

I tried today in the cockpit!

It's true.

Alex, you can try pulling the DC Bus1 or 2 breakers, and you'll see pumps stopping in pairs!