Boots – shoes – and leggings
Patent
1982-09-30
1985-10-01
Krass, Errol A.
Boots, shoes, and leggings
73304C, 73290R, 340618, 340620, 361284, 364571, G01F 2326
Patent
active
045450200
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention pertains to the instrumentation art and, more particularly, to an improved fuel gaging system.
One type of fuel gaging system used extensively in commercial aircraft employs a probe (or a set of probes) in the fuel tank, the capacitance of which changes as a function of the fuel level. Such systems have been based on the assumption that fuel density and its dielectric constant are related in a closely predictable way. FIG. 1 is a plot of fuel density versus dielectric constant and illustrates a straight line plot 10 which forms the basis for one such aircraft fuel gaging system.
The assumed relationship between fuel density and dielectric constant has, in the past, resulted in gaging errors within acceptable limits, usually less than one percent. At the time such gaging systems were designed, fuel was relatively inexpensive and the cost of transporting additional onboard fuel was not thought excessive.
With increasing costs of crude oil, the cost of transporting generous reserves to accommodate a gaging error has become less acceptable. Also, as crude oil is being used from new sources and a wider range of distillation fractions in jet fuels are being employed, the gaging error due to the assumed density/dielectric constant relationship has increased. Referring again to FIG. 1, a relatively recent survey of samples of jet fuel indicates that deviations from the assumed density/dielectric constant graph 10 can be as great as is shown in points X and Y.
In addition, capacitive probe type fuel gaging systems have been susceptible to errors caused by both stray capacitance and capacitance variances as components become wetted with fuel.
A yet further problem with gaging systems used on aircraft is that gaging errors are induced by the aircraft's attitude.
There is a need, therefore, in the capacitive fuel gaging art, particularly for use in commercial aircraft, for means to correct for the above-identified errors.
SUMMARY OF THE INVENTION
It is an object of this invention, therefore, to provide apparatus for, and a method of, correcting for fuel gaging errors resulting from deviances in the assumed fuel density/dielectric constant relationship.
It is an additional object of this invention to provide the above-described fuel gaging system, which system corrects for errors caused by stray capacitance and dry-to-wetted capacitance variances.
It is a further object of this invention to provide the above-described fuel gaging system, which system includes means to correct for errors induced by the attitude of the system.
Briefly, the invention is an improvement to a fuel gaging system wherein fuel quantity is determined by measuring the capacitance of a capacitive probe in the fuel tank and relating such capacitance to fuel mass by an assumed fuel density/fuel dielectric constant relationship. The improvement includes a means for producing a signal K representative of the actual dielectric constant of the fuel, a means for producing a signal D.sub.A representative of the actual density of the fuel, and a processor for processing the K and D.sub.A signals and determining whether the assumed relationship is valid for the particular fuel in the tank and, if the assumed relationship is invalid, applying a predetermined correction signal to the gaging system such that the system indicates actual fuel mass.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph illustrating the assumed relationship between fuel density and dielectric constant as used by a conventional fuel gaging system;
FIG. 2 is a schematic diagram of a conventional capacitive probe-type gaging system used in aircraft;
FIG. 3 illustrates by block diagram the improved fuel gaging system;
FIG. 4 illustrates various waveforms found in the apparatus of FIG. 3;
FIG. 5 is a detailed schematic diagram of the phase lock and decade counter circuitry shown in FIG. 3;
FIG. 6 is a detailed schematic diagram of the switch gating circuitry used in the circuit of FIG. 3;
FIG. 7 is a detailed schematic diagram of t
REFERENCES:
patent: 2769338 (1956-11-01), Hermanson
patent: 2866337 (1958-12-01), Minneman et al.
patent: 3463980 (1969-08-01), Cohn et al.
patent: 3527096 (1970-09-01), Cohn et al.
patent: 4090408 (1978-05-01), Hedrick
patent: 4173893 (1979-11-01), Hedrick
patent: 4235106 (1980-11-01), Maltby et al.
patent: 4258422 (1981-03-01), Dougherty et al.
patent: 4262531 (1981-04-01), Hewitt et al.
patent: 4350039 (1982-09-01), van Dyke et al.
patent: 4383444 (1983-05-01), Beaman et al.
Cosimano Edward R.
Donahue Bernard A.
Hamley James P.
Krass Errol A.
The Boeing Company
LandOfFree
Fuel gaging system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fuel gaging system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fuel gaging system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1445967