View Full Version : B-747-400 Fuel Info
flynhigh
22nd Oct 2006, 16:42
Hello All
Can someone explain the 400 fuel system or tell me where I can find the information. Thanks for any help
Spanner Turner
23rd Oct 2006, 08:50
Well, I could explain it to you! It may take me several years to type the post though! What in particular would you like to know? PM me and I may be able to forward some info in your direction.
As a starter:-
Overview
The Fuel System includes nine subsystems which control all fuel
related functions of the Airplane.
Fuel Storage Tanks
The Aircraft structure is used to store fuel. Construction features
include tank access, venting and sump drain valve installations.
Fuel Quantity Indication
Fuel quantity indication covers the Electronic System and
components used to measure, monitor, display and activate various
controls used during ground servicing or in-flight management of the
Fuel System. The manual method of determining the Aircraft fuel
load is also described in this subsystem.
Fuelling
Fuelling includes pressure fuelling control and operation as well as
manual (overwing) fuelling.
Engine Feed
This section includes the Fuel Supply System for Engine operation.
Also covered are System interconnections for operations such as
crossfeed, jettison and defuelling.
APU Feed
APU feed covers the APU Fuel Supply System, components and
operation.
Reserve to Main Tank Transfer
This subsystem covers the components required to transfer fuel from
the Reserve to the Main Wing Tanks.
Horizontal Stabilizer Fuel Transfer
This subsystem covers the components needed to fuel, transfer and
jettison fuel from the Horizontal Stabilizer Fuel Tank.
Scavenge
The Scavenge System equipment is installed to convert residual fuel
into usable fuel.
Jettison
Jettison is the in-flight system used for Aircraft rapid weight
reduction. Alternate jettison functions include fuel transfer, Engine
feed and defuelling.
JetMech
23rd Oct 2006, 14:42
Try page six of this link;
http://www.aaib.dft.gov.uk/cms_resources/Boeing%20747-436,%20G-BNLG%2006-06.pdf
It has a simple schematic of the fuel feed system of the B744.
machten
27th Oct 2006, 17:21
So, can you transfer fuel back to the HST from the main tanks?
spannersatcx
27th Oct 2006, 18:17
machten, no you can't.
gas path
27th Oct 2006, 18:52
..........unless your a ground engineer. Then anything is possible:}
tickler
15th Nov 2006, 13:47
Besides the obvious (more fuel and rear cg) are there any other advantages to carrying fuel in the stab?
can you dump from the stab?
spannersatcx
15th Nov 2006, 14:34
can you dump from the stab?
no, fuel from the stab goes to the centre tank when the centre tank reaches a set qty.
tickler
15th Nov 2006, 14:39
thanks spanner, saved me loads of time!
no, fuel from the stab goes to the centre tank when the centre tank reaches a set qty.
I disagree. Look at the wiring schematic flow chart, Spanners. During jettison, the CWT refuel valves are closed and if the fuel in the HST is greater than 1500lbs, the HST Isolation valves open. The HST is connected directly to the Jettison-Transfer manifold during fuel dump. The fuel in the HST will come straight out of the wingtips.
The CBT programs I've used also show fuel coming straight out of the HST.
Regards.
NSEU
spannersatcx
16th Nov 2006, 10:07
I was reading the question as can you dump directly from the HST, i.e. is it selectable.
Strictly speaking as NSEU states the fuel from the HST doesn't go to the CTR tank it connects directly to the refuel/jettison manifold.
However you can't directly dump just the HST which is how I saw the question, I was wrong in saying that it goes to the CTR tank, normal fuel transfer from the HST would however in this scenario it wouldn't. Hope that helps.:O
multi_engined
16th Nov 2006, 10:57
It burns lots of fuel :p
I was reading the question as can you dump directly from the HST, i.e. is it selectable.
Ahh.. perhaps I read it the wrong way?
I'm wondering what would happen if you activated the jettison system and switched off your O/J pumps (inboard tanks and CWT) for a short period.... Would you selectively dump fuel from the HST?
Regards.
NSEU
Redstone
17th Nov 2006, 00:51
I'm wondering what would happen if you activated the jettison system and switched off your O/J pumps (inboard tanks and CWT) for a short period.... Would you selectively dump fuel from the HST?
Regards.
NSEU
No. Simply because once a jettison is initiated a control relay is energised thereby activating the O/J pumps. You have to remember this is a "2 man crew", no flight engineer to organise and concentrate on such operations. Once the jettison is initiated the crew would dial in a "fuel to remain" figure which will then be the point at which the jettison ceases. If the O/J pumps are not allready selected on, then they will be comanded to on.
No. Simply because once a jettison is initiated a control relay is energised thereby activating the O/J pumps. You have to remember this is a "2 man crew", no flight engineer to organise and concentrate on such operations. Once the jettison is initiated the crew would dial in a "fuel to remain" figure which will then be the point at which the jettison ceases. If the O/J pumps are not allready selected on, then they will be comanded to on.
Sorry, but I disagree. On a 744, the O/J pumps need to be manually armed. Automatics can control the wing O/J pumps, but not if they are manually selected OFF. The CWT pumps are purely manual.
Perhaps you were thinking of another aircraft type? 767?
(Edit) Despite the absence of an F/E, we can assume that the pumps will be in a normal configuation for the fuel on board (i.e. all pumps manually selected on in tanks with fuel in them). EICAS messages will advise the crew to take action if the tanks become empty.
Regards.
NSEU
Looking at CBT's, wiring schematics and the description of pump operation in training notes, yes, it is possible to jettison fuel from the HST only (if you deselect the CWT and wing O/J pumps).
Why you would want to only do this is another matter :p
Regards.
NSEU
Redstone
19th Nov 2006, 00:28
NSEU you are quite correct, my bad, as you say though why would you do it? If you wanted to xfer gas from the HST into wing tanks quick sticks during maint, you could pull the nozzle cb's or pull the cannon plugs off the jet nozzles and set the system up as you described. Then just open refuel valves for tank to recieve fuel. Certainly though it would be not normal for crew to be doing such things.