Center tank fuel pumps?

[flygarn1 0]

Why does the center fuel pump switches switch to ON automaticly when I load fuel in the center tank. I know they are supposed to be on when there is fuel in the tank but why can't I switch them to on when the other pumps are supposed to be switched to on in the "before start" checklist?

Edited February 7, 2012 by flygarn1

[scandinavian13 5,192]

I believe your question can be answered here:http://forum.avsim.net/topic/355959-weekend-update-09dec11-ngx-sp1b-updates-available/page__p__2185344__fromsearch__1#entry2185344

Fuel system automatic switching logic after loading/unloading fuel from the FMC now conforms to FAA AD 2002-24-51.

[sheepfu 3]

When I load fuel via the fmc these switches flip on, but can be turned right back off.

[willywonka 36]

I believe your question can be answered here:http://forum.avsim.n..._1#entry2185344

That's the thing. It's been bothering me since the release. Not calling this a bug... I just don't know why PMDG did it this way.The quoted directive (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/8a9abde42a1e736a86256ca20060cb90/$FILE/022451fr.pdf) says that the center pumps must be OFF with 5000 lbs at T/O or 1000 lbs at climb and cruise or 3000 lbs at landing. When the FMC loads fuel into the center the pumps are switched on regardless of quantity.Are the pumps required to be on due to a refueling procedure or requirement?

[Spin737 102]

Are the pumps required to be on due to a refueling procedure or requirement?

No, they are not.Typically, at the gate if you're in the cockpit and running the APU, you can have a center pump on with any amount of fuel in the tank. This helps prevent an imbalance. For engine start, they're on if there's >1000lbs. On for T/O with >5000lbs, etc per the AD.I guess someone thought it'd be easier to have them turn on for some reason.

[oskrypuch 36]

Most 737NGs out there now have had modifications performed, such that the minimum center tank fuel AD (pump overheat) no longer applies.* Orest

[hp500 1]

Orest - Most have had modifications done, but some of the older pre-2002 frames with even older wiring/hardware can't be easily modified/retrofitted (time & $$$). Because of that, a lot of carriers still comply with this AD for standardization reasons, as their fleet may include aircraft from 1997 through today. So depending who's fleet you're modelling, the AD either applies or doesn't.I asked one of my my contacts to bring up this issue with PMDG not long after the initial release, as he's a Captain on the aircraft and also on the PMDG tech team. Apparently they refuse to change this logic to facilitate people who don't RTFM and know how to set up the fuel pumps correctly. IMO, that's a rather dumb reason... if someone can operate this airplane from A to B, or shoot an RNP approach, they can pretty easily learn how to manage two pump switches. It's not complicated, nor is it a 747 with a dozen tanks, so if they can't manage 2 pump switches, then they probably shouldn't be flying this airplane! I think this is simply overlooked by the tech team, because I don't think many (if any?) actually set out and do test flights that are long enough to warrant filling the center tank. I know my contact didn't notice it, because he generally does close-in routines or short 1 hour A-B runs for testing. I recommend we all submit a ticket about this - especially you Matt, since you're likely the only one of us who might carry any weight with RSR - and ask that this dumb automatic switching be disposed of for SP1c. Or at the very least, make it selectable in the realism options. It really dumbs down an otherwise technically excellent product. And no, the mechanical rocker switches (same as the wing fuel pumps) don't have servo's that make them move automatically, nor do invisible little men come into the cockpit and move them for you... ;-)

[scandinavian13 5,192]

Meh...what's the problem with just switching them back off...?As far as things go, the issue is pretty minor.

[EdubFlyer 2]

I didn't like that feature with the queen either, its more fun to learn the plane and know it.Eric

[davierosoft 13]

if someone can operate this airplane from A to B, or shoot an RNP approach, they can pretty easily learn how to manage two pump switches. It's not complicated, nor is it a 747 with a dozen tanks, so if they can't manage 2 pump switches, then they probably shouldn't be flying this airplane!

If you search the forum, there was a problem with fuel scavenge that was modeled with 10X fuel rate. I found it on the NGX because I did tests on it, other users, found it because they were flying with center pumps switched OFF.Now, PMDG did an automatic logic (that I hate) but few users are still capable to wrongly switch them off with fuel in it.

[flygarn1 0]

It just seem strange that the cockpit is VERY realistic and the center pump switches are modelled as lift and switch modell. And the thing with these switches in real life is that the plane can runt inte a mountain and the switches are still in the position they were before the crash when the plane is salvage, so they can't move by them self.How is it possible to manouver these switches in the wrong way if you have read the FCOM?

Edited February 8, 2012 by flygarn1

[davierosoft 13]

Personally I think that less than 50% of NGX users opened the documents included with the aircraft.There are a lot of simmers that are not interested in the simulation itself but about the 3d model and other graphical features.Others want to burn wings fuel before center tank, and so on...

[scandinavian13 5,192]

Personally I think that less than 50% of NGX users opened the documents included with the aircraft.

I'd agree with you, but I'd also argue that number is pretty darn high. Think of how many questions here could've been answered by the Intro manual, and how long is that?

[willywonka 36]

In the end, it doesn't really matter why. Just load the fuel, and go turn the centers OFF until you're ready to start.And you might as well follow the AD. If you read any of the airline's FCOM they follow that procedure anyway so there's really no getting around it.

[uhntissbaby111 58]

Where in the manuals can i read about managing the pumps? i looked through both the fuel section in FCOM 2 and both normal and supplementary procedures in FCOM1. did i miss it somewhere?adam