735 Fuel Management

[bfisk]

Hi all,

This might not be the appropriate forum - but I'll give it a try anyhow. As a flight instructor dreaming of bigger and better stuff, I often fly the 737 PIC package by Wilco for FS2004. It's supposed to be pretty realistic, is what they say anyhow. Have a scenario from here:

Took off from Malta enroute to Liverpool on a 737-500 with both L and R main tanks full, and about 6000lbs in center tank; a pretty good little fuel load for the 3.5 hr flight. Should leave me with about 1 hr reserve based on 6000lbs/hr fuel flow. Enroute I figured that for some reason fuel was only being fed from main tanks, not from center tank. Upon capturing glideslope into Liverpool I got Low Pres warning lights for left tank with associated master caution. Landed uneventfully and upon exiting runway, right low fuel pres warning lights came on. Hoping for fuel to now be routed from ctr tank, I continued taxiing to stand, only to find that left engine shut down when I tried to start APU. Right engine continued long enough for me to be able to reach my parking.

So; is it FS that is unrealistic or is there some magic to the fuel management I'm unaware of? The switches on the fuel management panel are 2x3 fuel pumps and a cross feed switch. How can I use center tank fuel?


Thanks =)

[chksix]

The center tank must be used first. You have to wait until it's below 1000 lb before drawing fuel from the mains.

http://www.smartcockpit.com/

[Denti]

The center tank pumps have a slightly higher output pressure so if you select all pumps on it should empty the center tank first. Dunno if others still use that tank schedule, but in "my" outfit we still have to have center tank pumps on if we have more than 1000lbs (or 453kg) of fuel in the center tank.

[I-2021]

Hi bfisk !

Nice software anyway, isn't it ? ;) Make sure you always use fuel in the center tank first, and then fuel from main tanks. This is simply done by selecting all 6 fuel pumps ON on ground. If you have less than 1000 lbs in the center tank upon starting your flight, don't care about it, use main tanks fuel and you will care about center tank fuel later on, during the flight.So that means center pumps OFF for the time. Once you level off in cruise and you have that small amount of fuel in the center tank, you can turn the center tank fuel pumps on and let the center tank get empty. It will not take too long:ok:

[yachtno1]

All 6 boost pumps are identical. Centre tank pumps over-ride main tank pumps due to the opening pressure difference across the check valve at the outlet of the centre tank pumps being less than the opening pressure difference across the check valves at the outlet of the main tank pumps. Quote from B737 Maint training Manual.:)

[CaptainSandL]

You are both right but it depends which generation of 737 you are referring to.

Quote from a certain book…

“With all pumps on, centre tank fuel is automatically used before main tank fuel. To achieve this, the NG centre tank pumps deliver at a higher pressure (23psi) than the main tank pumps (10psi). On the 1-500’s the centre tank pump check valves operate at a much lower pressure (1.3psi cf 12psi) allowing fuel to flow from this tank first.”

S&L

[yachtno1]

Fair play Cap the original question was about a -500 series but note your comments about NG ;)

[chksix]

I always fly them in real time.

Even when doing these kind of flights :8
SWA2968
Aircraft
Boeing 737-700
Origin
* Baltimore Washington Int'l [KBWI]
Destination
* Los Angeles Int'l [KLAX]
Route
LDN*J134*HNN*J134*STL*J24*MCI*J80*GLD*HGO
*HGO242027*HBU*J128*PGS

Duration
* 5 hours 46 minutes
2342 nm

[bfisk]

Thanks for replies all,

This is what I thought, that ctr tank overrides main tanks when all are selected on. Might simply have had the ctr tank fuel pumps in off position, but this would give low fuel pressure light and master caution too, wouldn't it?

As far as flying goes; I do actually (more or less) sit in front of the computer for the entire flight. I spend the time reading JAA ATP theory anyway, while making dinner and relaxing. Done with systems, pplant, electrics, human factors and met, just started on PoF.

Again thanks all - You guys have an amazing knowledge :)

[BOAC]

Might simply have had the ctr tank fuel pumps in off position, but this would give low fuel pressure light and master caution too, wouldn't it?

No - you will only get the light/caution with pump low output/fail. There is no warning that you have them switched off................ until the main tanks................................:)

[bfisk]

No - you will only get the light/caution with pump low output/fail. There is no warning that you have them switched off................ until the main tanks................................:)

Only option i see then is that I have simply flown with fuel pumps off on ctr tank for the entire flight. Guess I should get some checklists, huh :}

[MrBernoulli]

"I always fly them in real time."

Holy cow!

[cfmoverboost]

The low pressure lights for the centre tanks are only active when the pumps are selected on. When the centre fuel is used the MC illuminates and can be extinguished by selecting the pumps off. The Main pumps are always active, if the low pressure light illuminate you cannot extinguish the light until there's sufficient output again.