‘The fuel cells and engine oil cells were rubberized fabric self-sealing tanks.
The Mains and Oil tanks were not collapsing.
There were the six main fuel cells….
no 1 and 4 were a single cell…. cap 425 US Gals
The two inbd fuel cells were split to accomadate the landing gear…the inbd tanks were 212 gals and 213 gals..total 425 US Gals.
Tokyo tanks were composed of a set of 5 for the 1 and 4 engines
(again. flexible collapsing rubberized fabric)
and and a set of 4 larger cells for the inbd tanks as the wing was thicker for the inbd….
The set of 5 for the outbd engines capacity was 270 gals
The set of 4 for the inbd engines capacity was 270 gals
Total capacity was 1080
Total fuel capacity with Tokyo tanks was 2780
1700 mains (425 x 4)
Tokyo capacity 1080 1700 + 1080 = 2780
I count a total of 24 tanks…6 mains, 18 tokyo (9 each wing) = 24 tanks
The fuel transfer system was much simplifed…there were two selector valves with 4 positions each …one for left wing, one for right wing…one transfer pump located in bomb bay. A three postion switch controlled the transfer pump..(on off on)….installed so that if the fuel flow was FROM the left wing….the switch was moved in the direction the fuel was to transfer…I.E. toward the Right wing. Transfer rate was 15 gals/minute…to transfer 90 gals.( 90 divided by 15 = 6 minutes).
To transfer from No 1 to No 2, fuel HAD to be transferred first to opposite wing tank, the Selector valves repositioned and then back to No 2.
The Tokyo tanks had a hydraulic valve (normally closed) but when the lever was actuated, the valve was positioned OPEN, and the fuel then was gravity fed into the respective tanks…the tokyo tank for the inbd tanks..sometimes marked AUX fed first into the inbd aux and had a 1″ line coupling it to the inbd main…this required when refueling, to move from the main to the aux and then back to the main as the 1″ line was also feeding fuel to the inbd tank. This process was continued until both tanks (Inbd) were filled.
In ascertaining the partially empty inbd tankage, an average had to be computed due to the arrangement of the tanks…IE 2 Aux dipped level, 130 gals…no 2 main 140 gals…average 135.
The B-17 had as an indicating system, a Liquidometer, which was composed of float and xmttr similar to auto indicating systems…the positions were 1 Main,
2 Aux,2 Main, 3 Aux,3 Main and 4 Main….there was no indication for the tokyo tanks…A note of caution, was that the Mains had to be below 150 before xfrring from the tokyos (to prevent over filling the mains.
The Bomb Bay tank capacity was 410 gals US. (each)
I hope this answers your questions ….’
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