AIRCRAFT FUEL MEASUREMENT

摘要

A method of estimating a quantity of a liquid fuel in a fuel tank of an aircraft. A surface of the fuel is illuminated with light so that the light is reflected or scattered by the surface of the fuel onto an array of sensors. The light travels to and from the surface of the fuel via a measurement path containing a transmission medium. A measured time of flight is made at each sensor for the light which travels via the measurement path to that sensor. At least one of the sensors is illuminated with light via a reference path containing a transmission medium with substantially the same refractive index as the transmission medium in the measurement path, the reference path having a known reference distance which does not vary in accordance with the quantity of the fuel. A reference time of flight of the light which travels via the reference path to said at least one of the sensors is measured. The quantity of the fuel in the fuel tank is estimated in accordance with the measured times of flight, the reference time of flight and the known reference distance.