US Patent 7246495 Control system for gas-turbine engine

In the gas-turbine engine control system having first and second control channels each inputting the outputs of speed sensors and controlling supply of fuel to the engine based on the inputted outputs, four outputs generated by the sensors are compared with each other to determine whether three of the four outputs are within a range that allows the three to be considered identical, and the three are then compared with a remaining one to determine whether the four outputs are within the range that allows the three to be considered identical to the remaining one, and based thereon, each of the four outputs is determined to be the output that is usable in the fuel supply control. With this, through the three-value comparison and the four-value comparison, when the high-pressure turbine speed sensor or the like is installed by plural numbers, it becomes possible to accurately select the sensor output(s) that is usable in the fuel supply control, thereby improving the control accuracy.