Sign in to follow this  
James Bennett

Fuel management

Recommended Posts

When main tanks 2 and 3 become equal to 1 and 4, do I close off all four x feeds or do I leave the ones hidden below the "open for access" covers? It seems odd to me that you would run engines 1 and 4 from their respective tanks only but run engines 2 and 3 from both main tanks 3 and 3.

 

What's the reason for the cover over the buttons? I get a master caution if I switch those x feeds off.

 

Could not find answer in manuals, thanks.

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

When main tanks 2 and 3 become equal to 1 and 4, do I close off all four x feeds or do I leave the ones hidden below the "open for access" covers?

 

Before takeoff, all crossfeed switches are on. When you receive the FUEL TANK/ENG message and tank 2 is less than or equal to tank 1 or tank 3 is less than or equal to tank 4, turn the crossfeed valves 1 and 2 off.

 

Usually the only time that you would use a guarded switch is in the event of an abnormal/emergency procedure. In other words, if it's guarded, don't touch it.

What's the reason for the cover over the buttons?

 

I think the crossfeed valves 2 and 3 are automatically controlled by the fuel system controller. Display the fuel EICAS page before takeoff and extend the flaps. You can see the fuel system configure itself. The crossfeed valves 1 and 4 are manually controlled.

 

 

I get a master caution if I switch those x feeds off.

 

The message means that the crossfeed valve is not in the commanded position by the fuel system management cards.

Share this post


Link to post
Share on other sites

Hi James,

 

I shall give a full fuel management process description so that your question can be seen in context.

 

In the B744, the fuel system management cards (FSMCs) command fuel valves and pumps. The system logic is designed to automatically minimise wing bending and structural loads. However, crew actions are required during major fuel feed changes.

 

Pre-flight, when all tanks may be full, the crew push all valve and pump switches ON. When flaps are extended for takeoff, the FSMCs close crossfeed valves 2 & 3. Override pumps provide engines 3 & 4, and main tank pumps 2 & 3 provide fule to engines 2 & 3. When flaps are retracted, FSMCs open crossfeed valves 2 & 3, and override pumps in the centre tank provide fuel to all four engines.

 

When the centre tank quantity is decreased to 80,000 lbs (36,500 kgs), the FSMCs activate transfer from the stabiliser tank to the centre tank, and the override pumps in the centre tank continue to provide fuel to all four engines. When the stabiliser tank becomes empty, the message FUEL PUMP STAB is displayed and the PRESS lights are illuminated. The crew press both stabiliser tank pump switches OFF.

 

When the centre tank quantity is decreased to 2,000 lbs (900 kgs), the EICAS message FUEL OVRD CTR is displayed and low pressure lights are illuminated. The crew confirm the tank quantities and push both of the centre tank pump switches OFF. The fuel remaining in the centre tank is either then transferred to main tank 2 via an AC scavenging pump, or with a hydromechanical pump to main tanks 2 & 3 (customer option). FSMCs now activate override pumps 2 & 3 so that main tank 2 supplies engines 1 & 2, and main tank 3 supplies engines 3 & 4.

 

When main tank 2 or 3 quantity decreases to 40,000 lbs (18,100 kgs), the FSMCs activate transfer from reserve tanks 2 & 3 to the associated main tanks.

 

When the main tank 2 quantity is equal to or less than main tank 2 quantity, or main tank 3 quantity is equal to or less than main tank 4 quantity, the EICAS message FUEL TANK/ENG is displayed. The crew confirm the quantities, and push OFF both the override pump switches and the crossfeed valve switches 1 & 4. The main tank pumps now provide fuel to their associated engines until engine shutdown.

 

Note, the normal operations do NOT include crew interaction with crossfeed valve switches 2 & 3. Only on the rare occasion when the valve lights may glow amber would any crew interaction be appropriate, as this indicates that the FSMCs commanded valve position disagrees with the actual valve position. I do not believe that this is modelled in the current B744.

 

I hope that this explanation helps.

Good flying!

 

Edit: My explanation was concurrent to Kenny's.

Share this post


Link to post
Share on other sites

Thanks both of you, that was really helpful. Good to know i have been doing it correctly then. The background info was interesting too, sometimes it helps to understand why you're doing a particular action, not just how its done.

Share this post


Link to post
Share on other sites

Shameless plug for the section of the manual that describes all of this.

 

...then again, I thoroughly enjoyed Richard's write-up as well.

Share this post


Link to post
Share on other sites

Shameless plug for the section of the manual that describes all of this.

 

...then again, I thoroughly enjoyed Richard's write-up as well.

Thanks for that smarty pants, do you not think i read that before asking for further information? The manual explains which pumps etc to turn on but doesn't explain the crossfeed and override pumps as well as i'd like so i asked for further info.

Share this post


Link to post
Share on other sites

 

 


Thanks for that smarty pants, do you not think i read that before asking for further information?

 

I have seen people ask questions whose answers are plainly stated in the introduction PDFs.People do not read the manuals sometimes.

Share this post


Link to post
Share on other sites

I'm sure some people don't but i did state in my post that i had looked in the manual but needed some further explanation. There's always one smart alec who feels the need to comment.

Share this post


Link to post
Share on other sites

 

 


Thanks for that smarty pants, do you not think i read that before asking for further information?

 

It wasn't meant to be a smart reply, really.  The manual very clearly explains that only the crossfeeds between 1/2 and 3/4 need to be closed at FUEL TANK/ENG,  so it's a reasonable assumption that you hadn't read the relevant section of the manual.


 

 


There's always one smart alec who feels the need to comment.

 

It wasn't meant to be one, but it's your own prerogative to get upset about it.

Share this post


Link to post
Share on other sites

I believe that there are lots of people on this forum who are willing to spend some time helping their fellow simmers. But it only takes a moment to turn them off by using less well-meant language.

 

Let's try to keep things above the line.

Share this post


Link to post
Share on other sites

Right on - Richard!

 

The PDMG 747-400x is very good at consuming reserve and stab fuel first. The override pumps bypass the system from pulling from Tanks 1 and 4.  And at takeoff fuel system demands are extremely high so the override pumps should be on to satisfy that demand.

 

The caution panel fuel warning light that comes on is telling you that tanks 1 and 4 have more fuel in them than tanks 2 and 3. When that happens, I check to see what crossfeeds are open and then start using tank 1 and 4 exclusively. Of course that means you can't go on vacation and expect the airplane to still be in the air when you come back. But the airplane lands much better when the fuel load is closer to the centerline of the airplane but none is in the center tanks. The portion of the airplane that is the strongest is where the main landing gear is located so you should try to have most the fuel there. I have the lower EICAS panel open to "Fuel" most of the flight.

 

My RW Flight Engineer friends tell me to monitor the fuel load frequently. And if there is a choice, consume fuel from tanks 1 and 4 first once the center, reserve, and stab tanks are empty.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this