Abstract: A gas turbine engine control system sends a demand signal to a fuel throttle valve. The demand signal is modified by a measured fuel flow signal during normal operation. Operating parameters such as pump speed and recirculation valve portion are sensed. Combining these sensed parameters with the known geometry of the system, a calculated pressure differential between a point upstream of the throttle valve and a point in the combustor is determined. This calculated pressure differential is applied to the known geometry of the system from before the throttle valve to the combustor, including sensed opening of the throttle valve. A calculated flow is thus obtained and compared to the measured flow. An excessive difference between the measured and calculated flows indicates flow meter error. In such a case the calculated flow is substituted for the measured flow in modifying the demand signal.