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wijnand

Revised fuel system <> Original fuel system

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Hello guys,

 

In Kyle's video which showed the options in the upcoming 744v3, you can see the option for the revised or original fuel system.

 

I am curious to what is the differrence, mechanical and/or operational?

 

Regards,

 

Wijnand Lindelauf (EHBK) 

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I am curious to what is the differrence, mechanical and/or operational?

 

...and/or electrical :P

 

I can think of a few changes over the years...

 

1) The switch from an electrical Centre Wing Tank Scavenge pump to a hydromechanical system (not so new). I believe, at the same time, it was necessary to automatically turn on two inboard wing tank pumps during APU operation to prevent fuel imbalances.

2) a change in procedures after a series of fuel tank explosions (both engineering and pilot procedures)

3) (I think) a change in fuel pump types also to prevent explosions

4) a change in procedures, aircraft electrics and EICAS messaging (to prevent explosions)

 

Regarding 4), some of the EICAS messages are now based on fuel quantity rather than fuel pump low pressure. Also, timing circuits were introduced. If the fuel pumps run dry for a certain time (x seconds), the pump will be disabled. Even if you refill the fuel tank, it won't automatically restart. You have to cycle the pump switch to reactivate it (or take power off the pump circuit)

 

I'm wondering if the PMDG options change one or more of these?

 

Cheers

John H Watson

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You are a very wise man Mr Watson.  

 

The "Original" fuel system is the Pre AD fuel pump and messaging as the original 747-400 was configured with the exception of the Eicas messaging which had to be changed for the original AD rule to leave fuel remaining in the Center and Horizontal tanks.  Because of this, to remain legal in the eyes of the FAA, the user would have to shut off the pumps with fuel remaining in the Center and Horizontal Stab in accordance with the Boeing directive following TWA 800.   The Eicas messaging will alert you when you reach those levels.

 

The "Updated" fuel system incorporates all the AD requirements that were mandated as part of the final AD rule which includes added auto pump shutoff,  current limiters,  Revised pump motors and housings, Motive flow scavenge pumps and updated Eicas messaging.   The scavenge pumps were not technically related to the AD but an item that was installed by default on 747-400s after a certain line number so they were included in the Updated fuel system

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You are a very wise man Mr Watson.

 

 

Do not confuse wisdom with knowledge, Paul :Tounge:

 

But thanks for the compliment :smile:

 

Cheers

John H Watson

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hello gentlemen,

 

Thank you for your answers (you are both wise He%20He.gif !

 

If I look at the level of detail in this simulation, I can't help thinking back of the 80's, when we had Bruce Artwick's Sublogic Flightsimulator

on the Commodore 64.

 

It took about ten minutes to load the program, and during the loading (all 64K!!!!) you had to choose if yoy wanted ADF or VOR2 displayed!!!

 

A lot can change in 30 years!!

 

Regards,

 

Wijnand Lindelauf (EHBK)

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I still have the Flight Simulator II by subLogic box for the C-64 right here - seeing what a 1 MHZ PC could do w/ 64K of RAM made me change my major from Criminal Justice to Computer Science (great move by the way).  By today's standards it sucked; but....landing a plane with a frame rate of 1-2 FPS really made a person think "ahead of the plane"!   The C-64 at the time cost $200 but the 5.25 single sided disk drive that hooked up to it (and was required for loading FS) cost me $340.00 in 1984.  I spent months earning the money to buy it and I still have that drive in a closet.

 

Sorry to go off-topic but those old days bring back great memories.

 

As far as the new fuel system goes in our beloved new Queen Of The Skies, I suspect it is just one of many great details we'll get to slowly uncover as we spend time with the lady.  I predict that once the product is released that the forums will be flooded with folks claiming they have found a bug, only to learn the real aircraft would have behaved in the same way.  These forums are gonna explode upon release!

 

Mark Trainer

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Gents,

 

To add a bit to the discussion:

 

The "Updated Fuel System" covers behaviors as mandated on all 747-400s as of January 2016's mandated AD deadline.

 

I think most users will want this option selected, so that their operation will match the ckecklist.

 

For those simmers who want a bit of legacy simming, or who have the older checklists, you would want to select "Original."

 

Original is probably a bit of a misnomer- but the fuel system is essentially the original logic that shipped with the earlier line numbers, plus the software upgrade to add the protection messaging logic to remind the crew to leave fuel behind in various tanks for flash suppression... 

 

Either way- play with it.  I think you will find them interesting!

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