Patent ID: 7983829

Claim:
A system to monitor an output of a sensor for detecting an operating state of a gas turbine engine by comparing a value of an output of the sensor with a prescribed reference value, the gas turbine engine including a first shaft and a second shaft disposed in a coaxial relationship, comprising: a first shaft rotational speed sensor configured to detect a rotational speed of the first shaft; a second shaft rotational speed sensor configured to detect a rotational speed of the second shaft; an inlet air temperature sensor configured to detect a temperature of air at an inlet end of the engine; an estimating unit configured to estimate a rotational speed of the first shaft based on an output of the second shaft rotational speed sensor and an output of the inlet air temperature sensor, wherein the estimating unit comprises a calibration map configured to convert the output of the sensor detecting the operating state of the engine into a variable that can be used to control the engine, wherein the prescribed reference value is defined in the calibration map; a comparing unit configured to determine a difference between an estimated value of the rotational speed of the first shaft estimated by the estimating unit and an output of the first shaft rotational speed sensor; and a selection unit configured to select the detected rotational speed of the first shaft for use in the control of the engine when the difference is within a prescribed tolerance range, and select the estimated rotational speed of the first shaft for use in the control of the engine when the difference is beyond the prescribed tolerance range.