@FormerSnail5736 Sorry, now a different question 
I’m on my way from YBBN to YPAD in the 737-700 and that is about 1400 km flight, so I also need to have some fuel in the middle tank. In this case, do you wait till the fuel master warning + low pressure warning on the center fuel pumps to disable them or you disable the center pumps a bit earlier and leave some fuel in the center tank?
Last night I started a flight from KBWI to KPVD. Programmed the FMS as I always do. When I went into Legs to check the route, noted that there were no speeds or altitudes populated. I checked everything, couldn’t find any errors. Started over from scratch, no issues. Any idea what I missed on the first try?
As soon as one of the fuel pump low pressure lights flickers you can turn both center pumps switches off. The center pumps turn off automatically anyway as soon as the first low presure light comes on. If you don’t notice the first low pressure light then you’ll see “master caution fuel”. Turn the center pumps off. We don’t fly with any fuel in the center tank unless the wings are full.
Any fuel remaining in the center tank after the center pumps are off will be transferred automatically to the left wing by the scavenge pump once the wing is at roughly 50% capacity (this is completely transparent to the pilot).
I was asking because I remembered that I read this in the FCOM some time ago:
According to this I am supposed to leave 500 kg of fuel in the center tank, or I am just not understanding it well.
The second paragraph doesn’t make sense anymore or it might be a misunderstanding of the pre-flight procedure. It might be based on older 737s when the center fuel pumps didn’t have automatic shutoff. On current 737s the pumps turn off automatically as soon as the low pressure light flickers. We turn off the switches mainly to extinguish the low pressure light once the tank is empty.
Here’s a quirk about the center tanks in the 737. In the wings we can put 7.6 tons of fuel. Let’s say for a flight we want 8.0 tons. That means in the center tank there will only be 400Kg. That quantity is very low. So on the ground we may use the center pumps mainly for the APU (to prevent imbalance) but before pushback we will turn the center pumps off (and turn them on again at 10000ft or in the cruise).
This is because the acceleration of the take off roll and the attitudes during the first portion of the climb (12º to 20º nose up) can rush this small quantity fuel to the back of the tank starving the pumps. The pumps would then turn off automatically and we could get a “master caution/fuel” and “low pressure” lights in the middle of the take off maneuver. If that happens before 80kts we would reject the take off and look like idiots.
To prevent this, if the pilot considers that the amount of fuel in the center tank is not enough to keep the “low pressure” lights from coming on during take off, the center pumps switches are left off until the airplane is in flight at normal cruise or cruise climb attitudes. In my airline we turn them back on at FL100 (when we do our “10checks”)
Everything you said I already knew from the earlier discussions and I understand that. My question was that when you are on a longer flight and you have fuel also in your center tank if you just run the center tank empty (you leave the pumps on till the low pressure warning) or you just leave some fuel in the center tank and switch the center pumps off before the tank is empty and carry on using the fuel from the wing tanks. That FCOM part I sent is from Climb And Cruise procedure section and according to that I should leave 500 kg in the center tank. That’s why I’m confused.
I wonder how many people like myself… Love having a couple of craft IPA, not actually fly MSFS and just simply read these great posts…
All makes sense… I’ve been switching the central pumps on all the time when I see that there is a small amount of fuel in the tank and forget all about it as Im looking at the scenery until I catch the orange light of doom out the corner of my eye well after the last couple of mills have drained…
To the specific question of whether we turn off the pumps in cruise when the center tanks are at 500Kg my answer is: In my current and previous airline we turn the pumps off whenever we notice that the center tank is empty (Low Pressure lights, quantity indication or master caution).
Sometimes that happens when the low pressure light comes on but before master caution. Sometimes we don’t notice the low pressure lights and we do it when master caution lights up and some other times we do it before we see any lights only because we happen to notice that the center tank is at 0Kg.
Other airlines may do it differently of course. But remember the AFM limitation on this is that whenever the center tank has more than 453Kg (1000lbs), the wings must be full. So technically the manufacturer forbids to have 500Kg in the center tank and not have full wings.
Just for interest, I’ve uploaded a 737 landing challenge to
easily modified to use the -700 (or -800)
First is Skiathos but more will be added
And that’s why it’s bugging me. FCOM is issued by the manufacturer, isn’t it? But I can’t exactly determine what FCOM I have. There is no annotation. I just want to do things as close to the real procedures as possible, so I will let it run empty if you say it’s done like that in the real aircraft. Cheers.
After a three week holiday, I updated my 737-700 in the PMDG Operations Center to the latest version and set out to fly my first flight plan, but I am encountering a new problem. After going through the normal routine setup from cold and dark, I have found that my first officer displays largely are not active (they are not dark but show no flight plan on the MFD) and once airborne, I cannot get my autopilot to activate. I have rebooted several times, changed liveries and tried pretty much anything else I could think of, but to no avail. Has anyone encountered this problem and/or have any advice for me?
Try reinstalling. Usually when weird stuff like this happens, a reinstall might fix it. Pretty sure that the first thing the PMDG support would suggest.
Anyone has any issues with installing liveries and they do not pop up on the installed list and when you decide to delete them from the folder, they are still in tha game as you haven’t properly uninstalled them as they are not in that list
Good steer. I reinstalled the mod and it is working once again. Many thanks…
Yes, the FCOM is issued by Boeing but airlines can have it customized. My previous airline was a small one and our FCOM was “vanilla”. The airline I fly for now is huge and our FCOM is tailored for us and gets updated literally every couple of months. Of course the AFM limitations and systems descriptions listed in the FCOM do not change but airlines may add chapters to the FCOM and change things based on their SOPs. For example my old 2 volume vanilla FCOM didn’t contain amplified procedures (SOPs) and the the one I have now does.
I’m going to be in this forum for a while so if you want to know anything ask away. I grew up on MSFS in a world without internet and without IRL pilots in my life. I know how useful it is to have someone to ask questions so don’t hesitate.
Of course I can’t share my FCOM or I’d get in trouble bus use this one.
It’s old but it’s the best FCOM I have found online. Also try to get yourself a QRH and an FCTM. Those three manuals are must have.
Thanks. Having an IRL pilot so active in this thread makes this thread one of the best on this forum. Cheers.
You should come to the PMDG forum. There’s lot of IRL pilots there on the 737, 777 and 747.
The 500 kgs limitation is an “old” thing for the aircraft which don’t have the auto-shutoff pumps or modifications. I’m not sure if any of them is still around. Leaving that amount in the center tank makes sure you’re not running the pumps dry.
One potential issue was that eventually the scavange pump moved some of this fuel to the left main tank causing imbalance. It was fun.
A little correction: if you have only 400 kgs of fuel in the center tank you cannot use it for the APU on the ground either because of the 453 kgs (1000 lbs) limitation for the pump.
I believe center tank operations were modified by AD 2001-08-24 (and whatever EASA version that usually follows)
“For ground operation, center tank fuel pump switches must not be positioned to “ON” unless the center tank fuel quantity exceeds 1,000 pounds (453 kilograms), except when defueling or transferring fuel.
Center tank fuel pump switches must be positioned to “OFF” when both center tank fuel pump low pressure lights illuminate.
Center tank fuel pumps must not be “ON” unless personnel are available in the flight deck to monitor low pressure lights.”
Which modified the AFM and by proxy SOP that didn’t already do this.
Perhaps the confusion on when to turn it off in flight stems from the ground ops limitation above? The AD says you can run it to the lights in flight.
There’s also AD-2016-18-16 which mandated a retrofit of automatic shutoffs and stuff, but that only applies to the -100 through -500 series.
You are correct. So let’s change that to between 453Kg and 1000Kg we’d run the pumps for the APU on the ground and then we may turn them off for take off.
