Fuel crossfeed time

[Low-bypass]

Hi there
Can anyone tell me how to time the duration to crossfeed from one tank to the other?Is there any specific formula for that?Any help will be much appreciated

[hetfield]

Don't understand. Can you explain further?

[BOAC]

If you mean how long to have the x-feed open, it is simple maths based on engine fuel consumption.

[Tu.114]

Ok, I´ll bite.

You first add the fuel flow per hour of all the engines You intend to feed from the tank in question. Let me call this figure FF [kg/h] (substitute mass units as required).

Then You determine how much fuel You want burnt off the tank. Let me call that amount M [kg].

The time required to burn up M, assuming no power changes occur in the meanwhile, will be:

M divided by FF equals time required [h]. Multiply this with 60 to achieve the minutes required.

Of course, if You have no CrossFEED, but a CrossFILL installed with no published rate (as in the DH8), there is no real substitute for keeping an eye on the pumping process...

[Low-bypass]

Oh thanks Tiu that sounds very simple indeed

[Bob Lenahan]

Simple arithmetic, or, ?????
Bob.

[Capn Bloggs]

a CrossFILL installed with no published rate (as in the DH8), there is no real substitute for keeping an eye on the pumping process...
Lear 35 left>right>left>right! http://www.smilies.our-local.co.uk/index_files/cry.gif

[thedude1]

Making this way too hard.

Open the crossfeed and when the tanks are balanced, close the crossfeed.

Done.


You don't crossfeed a tank to the other tank but you crossburn/crossfeed from tank to engine. ie, buring 2 tanks to 1 engine. (For simplicity, I assume it is a 2 engine a/c)

[Tu.114]

Thedude1,
this is type dependent actually. A Crossfeed will allow feeding an engine with the contents of the other engines dedicated tank - this seems to be the more common option (used on F70/100 and apparently many other jets), while a Crossfill system will use some pumps (on the DH8, the auxiliary fuel pumps that are run during approach/takeoff) to pump fuel from one tank to another; the engines will always be fed from their own tanks.

Now in case of an engine failure, the Crossfeed on the Fokker was the easiest thing imaginable to use - just open the valve and leave everything else as it was; no need to worry about imbalance any more. The Crossfill on the other hand seems designed to provide the crew with more workload (like many other little details on the Dash) - You will need to manually transfer fuel from the dead engines tank to the live one every so often, minding the imbalance Yourself.

[de facto]

Crossfeeding is a supp procedure...so before turning and twisting knobs,read and do the supp,it will REMIND you to confirm there is no fuel leak:E