The turrets on the earlier models (B-17F) are supplied with F-l type cylinders having a capacity of approximately 14 cubic feet when fully charged to 450 pounds. Under these conditions a fully charged bottle lasts one man approximately 2 hours. (Note: these bottles are recharged from the ship's supply during flight, so it will not be possible to fully charge them after several hours of flight on oxygen. They will be no fuller than the pressure in the system from which they are charged--front left system for top turret; rear left system for ball turret).
Fig. 10
OXYGEN SYSTEMS B-17G
B-17G models are modified so that the turrets are supplied oxygen directly through a flexible hose -- the top turret from the front left system -- the ball turret from the rear right system. The same changes may be found in the ball turret of the B-24.
COMPUTING OXYGEN DURATION
Several members of the crew must be able to calculate the duration of the oxygen supply. The following simple procedure will permit a fairly accurate estimate of each systems duration. The figures are based on altitudes between 20,000 and 30,000 feet where the majority of your combat flying will take place.
G-1 CYLINDERS -- full charge 450 pounds -- each cylinder equals 5 man hours.
FORMULA: 5 (man hours) x number of intact cylinders x actual pressure/400 divided by number of men using oxygen from system = DURATION in hours.
Examples:
FRONT LEFT SYSTEM - 5 cylinders -- full charge to 450 pounds = 25 man hours.