B737CL fuel pump for APU ops

[martin_tapuska]

Dear all,
I had a discussion today about using of fuel pump while the APU is started. Some of the guys in company think it should be AFT 1, some FWD 1 and some that it can be even the AFT 2 or FWD 2 or any CTR (it's true if the crossfeed valve is open). Well, I have no arguments but I guess it should be the AFT 1.

What do YOU think, which one it should be? Thanks for reply in advance.

Cheers!

[aviatorhi]

You can use any pump you wish to pressurize the left manifold, as the feed from the APU is out of the left manifold. Noe that the APU fuel supply is nearest to the AFT1 pump, some maintain this makes this the "best" pump to use.

In reality this depends on a lot of things, the APU suction feed can sometimes "overpower" a distant/weak boost pump, which is why some maintain to use the nearest pump. This is rare, but can occur.

http://www.b737.org.uk/images/schemefuel.gif

[triple7BR]

If there was only one fuel pump that should be used, boeing would have written it in the fctm/fcom.. As you will see there, no restrictions you can also leave them all off and the apu will do its job (main tank 1 will supply the fuel)

[B737-800W]

Dear Triple7BR,

thats true BUT NOT on every aircraft. There are some aircrafts that you are allowed to operate the APU with the Fuel Pumps to OFF and there are some others which requires one Fuel Pump to be operating in parallel with the APU.
Which one to use? Just airmanship!!

3 greens
B737-800W

[Breakthesilence]

Sometimes, time permitting, allow for a couple of minutes talking to technicians :ok:

A good hint to prefer FWD Left main pump is that between the 2 left pumps, that one is the easiest to be accessed by the maintanance staff in case of replacement.

To get to the other one, they say, is far more complicated :E

However, you have no restrictions to use whichever pump you prefer, such as one on the right side (crossfeed open) to balance the fuel.

[b737NGyyc]

Unless you have AC ground power hooked up it will not matter which LH pump you put on as they are AC powered through Main Bus 1 and Xfer Bus 1. Some aircraft have a DC pump option to push fuel up the keel beam to the APU.

Personally if I have AC ground power hooked up I turn on all 4 main tank fuel pumps as part of the cockpit setup. If not I start the APU on battery with minimal other electrics on to preserve battery power, very important in our Canadian winters as you usually only get one shot to start the APU on batteries on cold mornings without ground power.

[misd-agin]

You turn all four main fuel pumps ON as part of 'your' cockpit setup??

What's Boeing say about 'their' cockpit setup???

[EW73]

As far as I am concerned, all NGs should run one AC fuel pump whenever the APU is running.
The APU has an internal DC fuel pump, but that is designed only for starting the APU on the battery, not for continuous use, otherwise it will fail over time.
The pressure supplied by any AC pump will override and stop the DC pump!
For me, LHS AC pump normally, RHS (with Xfeed valve open) when balance is needed, but with CWT fuel I use one of those pumps (when CWT fuel quantity is sufficient), that way I don't get any balance problems.
Cheers,
EW73

[b737NGyyc]

You turn all four main fuel pumps ON as part of 'your' cockpit setup??

I never used the word "mine" in my post I used the word "the". Maybe you should try writing something constructive instead of attempting to pick apart other people's posts.

My company's FOM states when it comes to fuel pumps.

"FUEL PUMP SWITCHES (for tanks containing fuel) - ON"

This is taken verbatim from Boeing's manuals.

[Lord Spandex Masher]

Bottom line is that IDFM, either/or. End of.