Going from memory, at about a 5 to1 ratio with the CWT tank. Not sure of the reason why but perhaps for balance.
Good memory. The actual ratio is 5.2-1
A 747-400 with full tanks (but no stab fuel) can carry ~ 180 to 190 tons of fuel (depending on density - about 53,600 US gallons). Stab fuel adds another ~11.5 tons (3300 gallons), or about a 6% increase. I don't know why you'd need stab fuel at ~130 tons unless as JammedStab notes it's for balance.
The software in the fuel system determines when the fuel starts to go into the stab tank. It can be between 125-132T of total fuel load, that the stab will start to be used. It will then go in at the ratio of 5.2-1 (CWT-STAB) Total fuel is approx 170 T w/ the stab tank, 160 T w/o. 13.3 in each of Main 1&4, 37.3 in Main 2 &3, 51.0 in CWT, 3.8 in the reserves, plus 10T in the stab (as installed). That using a SG of 0.785.
Last edited by dartman748; 3rd Jun 2014 at 20:38.