Fuel System Shorts

B747-400 Fuel System Briefing and Tutorial for Flight Simmers, Pilots, and Aviation Enthusiasts. PMDG B747-400 simulation is used to learn the basics of the fuel system showing the fuel panel and fuel synoptics of the Boeing 747-400.

[@ZazaBoeing747]

Thats was a masterpiece class! This should be in the actual CBT. Thanks for sharing!

[@subsonicflighttraining]

Wow, thanks Rafael!

[@marcotokoku1898]

that is the best in-depth explanation of how fuel system works during difference stages.

[@subsonicflighttraining]

Thanks Marco...

[@4ndroidG]

Thank you! Excellent video. More B747-400 System Briefing videos would be much appreciated.

[@subsonicflighttraining]

Thanks 4ndroid, if 1 person likes it, that is enough reason to do more on systems.

[@randy1622]

Fantastic video, thank you so much. It seems like PMDG has since fixed everything you pointed out in your video. Even got the brief „valve“ indication when you set the flaps.

[@subsonicflighttraining]

You are welcome, good deal on PMDG, yes these videos were a while ago...

[@christianwalsh8006]

Hey mate, your videos are fantastic! Watch them regularly. Weird question, but what does the triangle "science beaker" with the dots represent on the panel? Fuel jettison?

[@subsonicflighttraining]

Thank you so much! That is a visual representation or symbology that those pumps are the Override Pumps 2 & 3. During fuel tank to engine, we have to manually turn off Overrides 2 & 3 and close cross feeds 1 & 4, so this is just a nice visual method of confirming you are indeed turning off the Overrides. Since they have 2X the output of a main tank pump, they represent that with the fuel, or more of it in the funnel or beaker compared to the main tanks, not a weird question by the way…

[@clementrono1478]

This is quite informative. Earned a subscription from me!

[@subsonicflighttraining]

Thanks Clement, glad you find value in them.

[@christianpilon7725]

thank again :) for this i learn so much stuff from you .

[@subsonicflighttraining]

My pleasure Christian...

[@pelebar1636]

better then CPAT thank YOU so much>

[@subsonicflighttraining]

My pleasure!

[@jep1103]

Very interesting, very informative, very well explained, learned a lot 👍

[@subsonicflighttraining]

Thank you, glad you got some value out of my tutorials...

[@jep1103]

@@subsonicflighttraining well learning the fuel system from your vid got me across the atlantic yesterday 😊

[@subsonicflighttraining]

@@jep1103 Is there really only 1 track eastbound and 1 track westbound in the OTS now? Did you cross in a 74?

[@jep1103]

@@subsonicflighttraining Yes in a 74 using navigraph...Gatwick to Gander.

[@RmDIrSudoSu]

Hi great video, I've a question, at how many fuel left the PRESS annunciator light up for each fuel tank? I've looked into the FCOM and did not manage to find it. If you've an answer on that It would be really nice.

[@subsonicflighttraining]

To tell you the truth, I have no clue. In the past, you were taught what pressure would bring on a PRESS light. With glass jets, they only tell you a Fuel PRESS light means low pump pressure. The center tank pressure lights start to come on around 3000 pounds in the center tank. It is probably the same for the main tank pumps. The standpipe level in tanks 1,2,3,4 is 7000 pounds each in case you had a really big fuel leak, you would have 28,000 pounds, which would give you a little over an hour left when fuel reaches the standpipe level.

[@RmDIrSudoSu]

@@subsonicflighttraining Thanks you very much, I was looking for these information for works I'm currently on. And they are hard to find. I've found some very old 747 engineer panels manuals but they don't explain much more than the current FCOMs I've found.

[@subsonicflighttraining]

@@RmDIrSudoSu The only place you would probably find it is in a 747 maintenance manual. I used to have access to those at one time. They were nice to know information, but not necessary to know for pilot operations...

[@RmDIrSudoSu]

@@subsonicflighttraining Yes I got some maintenance manuals but there I did not find everything I need in there. I'll continue tu dig a bit more on the internet. Thank you :)

[@japiov1]

Dear SST, great and thorough video, best available on the topic. I guess I have 2 questions: 1. What is the function of the override pump besides the jettison mode? What is the difference with a normal fuel pump? 2. Is it harmful if the pumps stay on after their corresponding tank is empty? Well, that's actually 3 questiona. Looking forward to your response.

[@subsonicflighttraining]

The Override pumps are designed to be 2 times the pressure output of the main tank pumps, so if both main tank pumps and Override pumps are On and System Logic calls for them, the Override pumps will Override the main tank pump pressure and provide the fuel flow to the engine. Each main tank contains two AC-powered fuel pumps which run continuously when selected ON. A single pump supplies sufficient fuel to operate 1 engine at takeoff thrust conditions or two engines at cruise thrust. Main tank 2 and main tank 3 also contain two AC-powered override/jettison pumps. Each override/jettison pump supplies sufficient fuel to operate two engines during takeoff and cruise conditions. These are the main differences. Not sure on whether leaving a pump on for a long period of time will reduce pump life. Of course, we have procedures to turn off pumps at various times when no longer needed, like STAB TANK pumps, CENTER WING pumps, and #2 and #3 Override Pumps. The Main Tank Pumps stay ON all the time during Normal Operations...

[@japiov1]

@@subsonicflighttraining Thank you very much for the elaborate answer.

[@user-oy2bz5wm2b]

Al, I'm in the PMGD FREIGHTER 747-400, KSDF -EDDK. Getting a low fuel quantity message , but my progress page says I'll land at EDDK with 36,000 pounds of fuel. That's low? Typically and generally how many pounds of fuel should I land with? Regards....!

[@subsonicflighttraining]

On a long haul flight, typically anywhere from 20,000 to 30,000 pounds depending on weather...

[@user-kj2it3qy6u]

Great video! One question: Why are crossfeeds 1&4 closed? Boost pumps 2&3 can't override the pumps in 1&4... Thx in advance!

[@subsonicflighttraining]

Thank you! I assume you are referring to tank to engine configuration. Override 2&3 pumps have 2 times the output pressure of Main Tank Pumps 1, 2, 3, and 4. So when you have all pumps ON and all cross feeds open, override/jettison pumps 2 provide fuel to engines 1&2, and override/jettison pumps 3 provide fuel to tanks 3&4. When we go tank to engine we turn off 2&3 override pumps and we close cross feeds 1&4 to ensure that main tanks feed their respective engines for the rest of the flight as all tanks are relatively equal at that point.

[@user-kj2it3qy6u]

@@subsonicflighttraining Thx! But why are the crossfeeds of 1&4 closed, if they're left open it would still be tank to engine. As boost pumps 2&3 can't override boostpumps 1&4 (unlike the override pumps which are turned off for tank to engine config).

[@subsonicflighttraining]

Yes, that’s true, but there can be differences in pump pressures between the main pumps, so to ensure the differences are somewhat isolated, cross feeds 1&4 are closed, so that main tank pumps 1&4 feed engines 1&4 respectively and are truly tank to engine and main tanks 2&3 feed their respective engines and keep the cross bleed manifold pressurized. This way if there are small differences, they would show up as a small lateral imbalance between the inboard tanks instead of the outboards, which is no big deal at all in the 747. Even large lateral imbalances are not a big concern, but we get warnings for imbalances of 3000 pounds for the inboard and 6000 pounds for the outboard tanks.

[@user-kj2it3qy6u]

@@subsonicflighttraining Thank you!

[@blueskyes747]

What is the pressure of the forward and aft fuels pumps in tanks 1,2,3,4. What is the pressure in the Override/Jettison pumps??

[@subsonicflighttraining]

To tell you the truth, I have no idea what they are. I saw it once in a maintenance manual, but I can’t remember what it was. In teaching the fuel system , Boeing does not tell you specific pressures, but just relationships. So, they tell us the Override pumps have 2X the output pressure as the main tank pumps. Over the years, specific numbers and system details have gone from building the system to knowing how to operate the system in normal and non-normal configurations, basically what the pilot needs to know in operating the system…

[@Hk-uw8my]

Hi,do the stab fuel tanks are in this aircraft for "trim" purpose in cruise like the a330 or a340 or only for an extended fuel capacity?

[@subsonicflighttraining]

The 22,000 pound Stab Tank is for extended range...

[@Hk-uw8my]

@@subsonicflighttraining ok thanks

[@chrissteer001]

Is the -8 fuel system much different? Is there a different emptying schedule? Thanks

[@subsonicflighttraining]

There are differences, but it operates identically to the 400 as far as flight crew operation. Differences include Reserves 1&4 instead of 2&3, a Nitrogen Generation System for the center tank, more fuel quantity, etc...

[@kanamekiyru]

Our level D sim is having a fuel jettison issue but we keep getting a fault so here we are. Watching videos on how to fix it

[@subsonicflighttraining]

What kind of fault, I am not sure my video will solve an issue in the Level D Sim that your maintenance folks can.

[@kanamekiyru]

@@subsonicflighttraining jettison auto on a 777. Goesboff every time we arm the jettison valve

[@subsonicflighttraining]

@@kanamekiyru Sounds like an annoying problem. I assume the Total Fuel Quantity is Greater than the FUEL to REMAIN? If so, then sounds like the input from one of the tank quantities might not be there in the sim card that controls that, but I am guessing. You can get that message if the Total Fuel is the same or less than the FUEL to Remain...

[@kanamekiyru]

@Subsonic Flight Training its actually telling us add more. So well drop to lets say 175kg it'll say it needs to release until it hits 200kg which is more than whats in the tanks

[@subsonicflighttraining]

I don’t have a clue, can the sim techs fix it?

[@chrisl5483]

What’s the reason for the center tank to eng 1-2 And tank to engine 3-4 during takeoff

[@subsonicflighttraining]

I think you mean the Center tank pumps to engines 1&4, and engines 2&3 are tank to engine when cross feeds 2&3 close automatically when the flaps reach the takeoff flap setting of 10 or 20. To tell you the truth, I’m not sure why we do that, there is nothing in the FCOM that explains why we do that. I suspect since the wing dihedral cants upward from the root and engines 1 and 4 are further out on the wing than 2 and 3, using the full might of the Center Tank Pumps at 2X the pressure compared to 1 and 4 main pumps, helps ensure a positive flow during takeoff with a relatively big angle of attack change at rotation and climb out, that’s my guess...

[@user-oy2bz5wm2b]

Al, upon investigation, I messed the fuel load up. I changed the quantity in the FS ACTIONS FUEL PAGE to a different quantity, however that quantity did NOT change the pounds in the actual plane, so I think that was why I got the low FUEL message. They need to agree. My fault!!

[@dangeroustoaster2688]

I'm playing flight sim 2020 and the STAB tank won't transfer to center automatically

[@subsonicflighttraining]

I know nothing about the new Flight Simulator. The accuracy I would expect to be not as detailed as PMDG or Aerowinx...