Patent ID: 8777165

Claim:
An aircraft fuel system comprising: a. a fuel tank with first and second cells separated by one or more baffles, the baffles permitting the flow of fluid between the first and second cells; b. a venting system for reducing any pressure difference between an interior and an exterior of the fuel tank, the venting system comprising one or more vent nozzles which are positioned within the fuel tank and in fluid communication with one or more vent ports, wherein the venting system has a venting capacity associated with each cell, and wherein the venting capacity associated with the first cell is greater than the venting capacity associated with the second cell, which may be zero; and c. an inerting system comprising: i. one or more gas sources for generating oxygen-depleted gas; ii. one or more inerting nozzles for injecting oxygen-depleted gas from the gas source(s) into the first cell, where F1 is the sum of the oxygen-depleted gas flow rates from the inerting nozzle(s) into the first cell; iii. one or more inerting nozzles for injecting oxygen-depleted gas from the gas source(s) into the second cell, where F2 is the sum of the oxygen-depleted gas flow rates from the inerting nozzle(s) into the second cell; and iv. a control device for varying the ratio F1/F2 between the flow rates into the first and second cells, wherein the one or more vent nozzles comprise a large vent nozzle in the first cell and a small vent nozzle in the second cell with a smaller cross-sectional flow area than the large vent nozzle, wherein the large vent nozzle is arranged so that gas can be vented from the first cell during ascent of the aircraft through the large vent nozzle and so that air can be fed into the first cell during descent of the aircraft through the large vent nozzle, and wherein the small vent nozzle is arranged so that gas can be vented from the second cell during ascent of the aircraft through the small vent nozzle and so that air can be fed into the second cell during descent of the aircraft through the small vent nozzle.