A Current Survey of Aircraft Fuel Gauging Systems 670263
Fuel gaging systems in over 90% of small civil aircraft use the automotive float type sender with an electrical indicator. Considering such factors as dihedral, summing, temperature, variation in specific gravity of fuel used, and input voltage, the accuracy is approximately ±5% of full scale and ±10% of the reading. A more accurate system is highly desirable for weight control, flight planning, and possible c. g. consideration.
Among other gaging systems available are improved float types at moderate costs, capacitive systems with good accuracy at comparatively high initial cost and increased maintenance, and a mass sensing system at moderate cost. The pros and cons of each system are discussed.
Factors contributing to errors in readout and often overlooked are variations in height versus volume of fuel tanks because of manufacturing tolerances, and changes in shape and relative position of tanks under different loading when in flight.