Smiths Group Plc

Smithgroup, Inc.

Harry Atkinson

An ultrasonic fuel-gauging system has several probes each having a transducer mounted at the lower end of a still well. The transducers are connected to a processor, which measures the height of fuel above the transducers within the still wells. The processor also measures the resonant frequency of each transducer and from this calculates fuel density. The system calculates the mass of fuel in the tank from the density and the volume as calculated from the heights.

Fluid-quantity gauging

An ultrasonic fluid-gauging probe has a still well and two or more piezoelectric transducer elements mounted at its lower end. A drive and processor unit may separately energize each element and provide a separate output indicative of fluid height so as to provide redundancy. Alternatively, one element may be energized and the other used to receive the reflected signal in normal use but, when a fault is detected, one element may be used to both transmit and receive. The elements may be mounted side-by-side, such as on a common substrate, or one above the other in a stack.

Fluid-gauging probes

An aircraft ultrasonic fuel-gauging system has a processing unit that energizes probes and receives signals from transducers arising from energy reflected back from the fuel surface. In addition to determining the time between transmission of a signal from the transducer and reception of its reflection from the fuel surface, the processing unit also determines the time of reception of subsequent reflections caused by reflection back from the lower end of the probe. The processing unit determines whether the subsequent reflected signals are within predetermined limits of the time interval between transmission and reception of the first reflected signal in order to confirm the validity of the first signal. The processing unit also counts the number of subsequent reflected signals received within predetermined time intervals to assign a confidence level and this used to select between different incompatible signals, such as signals from that probe at different times or signals from different probes.

Acoustic fluid-gauging system

An aircraft fuel-gauging system has multiple ultrasonic gauging probes providing fuel height outputs at several locations within a tank. The output of an inertial sensor is used to compute the attitude of the fuel surface with respect to the tank. The system uses the attitude information to determine whether outputs from a group of two or more probes are compatible with one another. Where a probe is identified as having an output incompatible with the fuel surface attitude and the outputs of other probes its output is excluded from the computation of the fuel quantity.

Fluid-gauging systems and methods

An aircraft fuel-gauging system has flowmeters at the inlet and outlet of a fuel tank. The output of the flowmeters is used to compute the height and volume either of a localised elevated region above the inlet, where fuel flows into the tank, or of a localised depressed region above the outlet where fuel flows out of the tank. Where the gauging probes are located away from the region of the inlet or outlet, the volume derived from the probes is corrected by adding the volume of the elevated region or by subtracting the volume of the depressed region. Where the gauging probes are located in the region of the inlet or outlet, the height output of the probe is corrected either by subtracting the height of the elevated region or by adding the height of the depressed region. The volume is computed from these corrected heights and further corrected by adding the volume of the elevated region or by subtracting the volume of the depressed region.

Fluid gauging

An aircraft fuel quantity gauging system has a number of probes within a tank to measure the height of fuel at different locations. Each probe includes a still well and an ultrasonic transducer mounted at the top and bottom of the still well. The lower transducer transmits pulses of acoustic energy upwardly through the fuel to its surface and measures the time of travel back of the reflected pulse back to the transducer. This is used to derive a first, bottom-up measure of fuel height. Similarly, the upper transducer transmits pulses down through air to the fuel surface to derive a second, top-down measurement. These are compared to check for correct operation of the probes.

Quantity gauging

An aircraft ultrasonic fuel-gauging system has a number of gauging probes in a tank arranged so as to include at least one set of three colinear probes. The outputs of the probes are supplied to a unit, which checks the operation of the probes in colinear sets by extrapolating height at one of the probes from the outputs of the other probes. Where there are two sets of colinear probes having a common probe it is possible uniquely to identify if the common probe is faulty. The system rejects any faulty probe and uses only the outputs of other probes in computations of fuel quantity.

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Berkshire, United Kingdom

Harry Atkinson