Abstract: A turbine fan speed monitor for use with an aircraft engine which monitors actual fan speeds for each of a plurality of aircraft engines. The apparatus also input instantaneous values of total air temperature, pressure altitude, altitude rate, and the position of the wheels. The fan speed monitor calculates an overspeed limit value for the turbine fan as a function of each of the total air temperature, pressure altitude, altitude rate, and position of the wheels data and indicates when the actual fan speed exceeds the overspeed limit value for each monitored engine. The monitor warns the pilot of calculated overspeed conditions that he can control by throttle manipulation. Engine life is related to the calculated speeds at take-off, climb and cruise. The monitor keeps a record of the time and duration of these instances when the actual fan speed exceeds the overspeed limit for any engine.