次日航前，发动机启动后控制灯亮，触发信息为73-44634 FAN SPEED (N1) SENSOR LOW TOOTH SIGNAL IS INVALID和77-43024FAN SPEED (N1) SENSOR IS OUT OF RANGE 。
73-44634 FAN SPEED (N1) SENSOR LOW TOOTH SIGNAL IS INVALID
(1)The low tooth signal that indicates fan position has failed.
(2)The low tooth signal amplitude is not sufficiently different from the other tooth signal amplitudes. Selected N1 must be valid and be greater than 34%.
(3)The fault is also set when 67% of single channel N1 sensor data contained noise for more than 90 cumulative seconds and the engine is running at or above idle.
(4)The fault is inhibited if the N1 sensor out of range (77-4302X) or the N1 soft sensor shift fault (77-4301X) is set. The cumulative persistence is latched until an EEC power cycle.
(5)The EEC resets the cumulative noise count after each power cycle, which typically occurs after the engine is shut down. If the EEC power is left on through multiple consecutive flights, normal levels of sensor noise may accumulate enough time to set this fault. It is important to check for indications that the EEC power was left on prior to performing additional fault isolation. Additional fault isolation is not necessary when this fault is set due to power that is accidentally left on.
77-43024FAN SPEED (N1) SENSOR IS OUT OF RANGE
(1)Engine fan speed (N1) signal exceeds valid range (less than 0.00% below idle or 4.36% above idle, or greater than 141.50%) or EEC input circuitry is failed.
(2)The fault will also be set if the engine fan speed (N1) signal on both channels have been invalidated due to exceedance of noise.
