I have a few questions regarding when to turn on/off the centre tank fuel pump switches before takeoff and in flight.

 

Loading left, right and centre tanks with 2,800kg's ea which give around 8,400kg's fuel total pre flight.

 

My questions are

1. When to turn off centre tank pumps off in flight ? Before x kg's left over or when amber warning message appears ?

 

2. Before takeoff if less than 2,300kg's centre tank fuel switches off ? Back on after 10,000ft ? Found this in an alt FCOM under Amplified Procedures but could not find any info in PMDG-NGX FCOMv1 or 2 nor the FCTM. If I have missed it, can someone give me any page references please.

 

Not sure what's correct as it say's if the centre tanks were off for takeoff and centre tank contains more than 500kg's turn them on above 10,000ft ?

 

Anyone that can arrest my confusion, much appreciated.

Thanks

Vojislav

When the centre tank reaches 1000lb's (454kg, make it 450) turn off the pumps, before Amber so the pumps don't run dry. Scavenge pumps will later removed the fuel if your wing tamks get low.

 

The reason you turn off pumps on ground below ~2000kg is so the centre pumps don't run dry on takeoff when you steeply pitch up on departure, turn them back on at 10,000 as the pitch is reduced. Later turn them back off when the centre tank approches 450-500kg.

 

 

Just curious why did you evenly fill all three tanks and not just top up the wing tanks and the remainer goes into the centre?

 

Eg

 

Left wing 3910kg

Right wing 3910kg

Centre 580kg (leave pumps off, atleast after taxi)

 

= 8400kg

The reason you turn off pumps on ground below ~2000kg is so the centre pumps don't run dry on takeoff

 

It's so you don't expose a potentially damaged fuel pump to fuel vapors, just not so the tanks don't run dry.

 

I think the procedures changed when the NGX was upgraded to SP1c. I could be wrong though..

 

Turn the center pumps on before engine start if the fuel amount is more than 1000 lbs (turn them off if the LOW PRESSURE lights remain on).

 

During climb, if a LOW PRESSURE light illuminates, turn the respective pump off. Turn both pumps off when then LOW PRESSURE lights illuminate and the tank is empty.

 

During cruise, if the center tank contains usable fuel, turn the switches back on. During cruise, if a LOW PRESSURE light illuminates, turn the respective pump off. Turn both pumps off when then LOW PRESSURE lights illuminate and the tank is empty.

hi voj. here are the limitations we use on the 737ng.

 

1st limitation...main tanks scheduled full when over 1000lbs in center tank.

 

the next procedures are hownwe operate the center pumps due to an AD (airworthiness directive)

 

1 for takeoff if less than 5000lbs in center tank, pumps OFF. when you get the plane cleaned up

gear/flaps,,,then center tanks back on.

 

2. in cruise, when the center tank fuelmgets to 2000lbs of fuel, open crossfeed valve,

and turn OFF 1 center pump. when the low press light in the center pump illuminates

turn off that pump.

 

3. in descent, if less than 3000lbs in center tank, turn off both pumps.

if you have to level off for a while, if less than 3000lbs, you can turn on 1 centernpump

again.

 

hope this helps you somewhat. i know Boeing has or is working on

a modnsomwe don't have to do this procedure...but not yet

 

best

David

 

Hello everyone,

 

you might also want to have a look here: http://forum.avsim.net/index.php?/topic/372029-Center-tank-fuel-pumps

 

That's the procedure currently used with FS2Crew, so it seems Boeing have implemented something.

 

So long,

Oli

 

 

Oliver Branaschky

Just curious why did you evenly fill all three tanks and not just top up the wing tanks and the remainer goes into the centre?

 

Eg

 

Left wing 3910kg

Right wing 3910kg

Centre 580kg (leave pumps off, atleast after taxi)

 

= 8400kg

 

No reason, just thought of even distributions to all tanks and experimental once centre is depleted to put into practice correct procedure.

Normally you would fill wing tanks to max regardless, and remainder in centre ?

 

During climb, if a LOW PRESSURE light illuminates, turn the respective pump off. Turn both pumps off when then LOW PRESSURE lights illuminate and the tank is empty.

 

During cruise, if the center tank contains usable fuel, turn the switches back on. During cruise, if a LOW PRESSURE light illuminates, turn the respective pump off. Turn both pumps off when then LOW PRESSURE lights illuminate and the tank is empty.

 

This is what I am currently doing, waiting for centre tanks to empty and switch pumps off when the amber alarm lights up, I wasn't confident that this was correct after reading another Boeing FCOM ?

 

2. in cruise, when the center tank fuelmgets to 2000lbs of fuel, open crossfeed valve,

and turn OFF 1 center pump. when the low press light in the center pump illuminates

turn off that pump.

 

3. in descent, if less than 3000lbs in center tank, turn off both pumps.

if you have to level off for a while, if less than 3000lbs, you can turn on 1 centernpump

again.

 

hope this helps you somewhat. i know Boeing has or is working on

a modnsomwe don't have to do this procedure...but not yet

 

best

David

 

What is actually happening when turning off 1 centre pump ? Crossfeed open, would that pull fuel out of centre tank to wing tanks ? Would you get both pump lights illuminate ?

 

you might also want to have a look here: http://forum.avsim.n...tank-fuel-pumps

 

Oliver Branaschky

 

Will have a read.

 

 

Thanks

Voj

The 2000kg limitation for center tank fuel with pumps on is old. NGs now have auto-shutoff fuel pumps and nitrogen inerting for the center tank so, effectively, the risk of dry pumps has been removed. If more than 450kg on the ground, center pumps should be on. If just 800kg or less expect a fuel master caution on takeoff or climb, this is expected and should be ignored.

 

The center pumps come off in flight with an amber LOW PRESSURE light and 0 indicated in the tank.

Correct, you can run the centers until they dry.

I know this is an old topic, but I know that this is a subject which has multiple correct answers, possibly resulting in damaged fuel pumps.

The 737NG has no auto shut-off fuel pumps. But there is a modification from Boeing which gives the aircraft auto shut-off fuel pumps. I guess most 737 in RW are now fitted with the modification. If it's not, you would see a yellow plackard under the ND, like this > http://www.pbase.com/flying_dutchman/image/95067727/original

It says: "Fuel usage restriction required"

This means you have to turn the centre fuel pumps off before take-off if centre tank fuel is less than 2.300kg. Turn then back on at 10.000ft and off again when the tank reaches 540kg (as discussed earlier here).

 

 

Richy

 

 

If it's not, you would see a yellow plackard under the ND, like this > http://www.pbase.com...067727/original
It says: "Fuel usage restriction required"

That's a good example, but that's simply how that operator chose to and was approved to comply. There are other placards and locations.

Just this month American changed how we operate the center pumps. At the gate we can not run them unless there is at least 1000 lbs in the center tank. From push back to gate arrival we now turn the center pumps on if there is any fuel in the center tank until we see a low pressure light. All the planes have been modified so that a Master Caution will illuminate even if only one pump center has low pressure plus if there is low pressure for ten continuous seconds the pump will automatically shut off. So far only the planes that were delivered with the nitrogen generating system have that system. None of the older planes have been modified. I get mixed reports on whether to old planes will be modified to include NGS.