Abstract: One or more main aircraft fuel tanks are provided with one or more fuel gauges arranged to provide a measure of the amount of fuel in said one or more main fuel tanks. One or more auxiliary fuel tanks are also provided. The aircraft uses fuel during a first phase of fuel consumption, upon commencement of which phase the auxiliary fuel tanks hold fuel. After the first phase said one or more auxiliary fuel tanks are empty and a second phase commences. During the first phase, an indication of the amount of fuel carried by the aircraft is provided by means of summing (i) the amount of fuel in the main fuel tanks as measured by said one or more fuel gauges and (ii) the amount of fuel remaining in said one or more auxiliary fuel tanks as calculated using a measure relating to the fuel consumption rate. During the second phase of fuel consumption, an indication of the amount of fuel carried by the aircraft is provided on the basis of the amount of fuel measured by said one or more fuel gauges.

Abstract: Unsafe electric energies can exist in aircraft fuel tanks as a result of static build-up or induced currents from lightning strikes. The invention provides an aircraft fuel tank including two discharge paths for the safe discharge of electricity from the tank before it reaches levels where an arc, spark or other electric discharge, able to ignite fuel in the tank, could occur. The failure of both the discharge paths would significantly increase the risk of an ignition causing electrical discharge occurring. The tank thus also includes a circuit for monitoring the integrity of each discharge path. By having at least two discharge paths, should one discharge path fail (which failure being detected by the monitoring circuit, at least one alternative discharge path exists for the safe discharge of electrical energy from the fuel tank, until the failed discharge path is repaired.

Abstract: Unsafe electric energies can exist in aircraft fuel tanks as a result of static build-up or induced currents from lightning strikes. The invention provides an aircraft having a ground circuit 19 and including a fuel tank having a fuel probe circuit having its own ground circuit. Multiple discharge paths allow the safe discharge of electricity from the tank before it reaches levels where an arc, spark or other electric discharge, able to ignite fuel in the tank, could occur. The discharge paths all pass via a conductive foam having a relatively high impedance that allow static bleed, but does not significantly increase the risk of currents induced by lightning reaching levels at which an ignition-causing electrical discharge might occur. The foam is securely bonded to both the aircraft ground circuit and the fuel probe ground, the bonds having a large area of surface-to-surface contact.

Abstract: A method of detecting a fuel leak from a fuel store of an aircraft where a processor receives inputs relating to the amount of fuel in the fuel store and to the rate of fuel used by the aircraft. The processor defines a fuel flow system state defined by a noise-compensated measures of the amount of fuel in the fuel store, a fuel leak amount estimate and a fuel leak rate estimate. The processor periodically calculates a new estimated state of the system in view of a previous estimated state and values of the inputs. The processor monitors the fuel leak amount estimate and the fuel leak rate estimate and if either exceeds a respective threshold value send a signal to a fuel leak warning device.

Abstract: One or more main aircraft fuel tanks are provided with one or more fuel gauges arranged to provide a measure of the amount of fuel in said one or more main fuel tanks. One or more auxiliary fuel tanks are also provided. The aircraft uses fuel during a first phase of fuel consumption, upon commencement of which phase the auxiliary fuel tanks hold fuel. After the first phase said one or more auxiliary fuel tanks are empty and a second phase commences. During the first phase, an indication of the amount of fuel carried by the aircraft is provided by means of summing (i) the amount of fuel in the main fuel tanks as measured by said one or more fuel gauges and (ii) the amount of fuel remaining in said one or more auxiliary fuel tanks as calculated using a measure relating to the fuel consumption rate. During the second phase of fuel consumption, an indication of the amount of fuel carried by the aircraft is provided on the basis of the amount of fuel measured by said one or more fuel gauges.

Abstract: A method of detecting a fuel leak from a fuel store of an aircraft is described. In the described embodiment, a processor (1) receives inputs (2, 3) relating to the amount of fuel in the fuel store and to the rate of fuel used by the aircraft, both inputs being subject to noise. The processor defines a fuel flow system state defined by a noise-compensated measures of the amount of fuel in the fuel store, a fuel leak amount estimate and a fuel leak rate estimate. The processor (1) periodically calculates a new estimated state of the system in view of a previous estimated state of the system and values of the inputs (2, 3). The processor monitors the fuel leak amount estimate and the fuel leak rate estimate and if either exceeds a respective threshold value send a signal to a fuel leak warning means (4). The method employed in the embodiment employs a recursive state estimation method that improves leak detection, reduces false alarms and is less demanding on processor and memory requirements.