Fault detection for a speed sensing system of a multi-engine rotorcraft

A system for performing fault detection for a speed sensing system of a multi-engine rotorcraft having at least one rotor, the system comprising:

• a processing unit;
• and
• a non-transitory computer-readable medium having stored thereon program instructions executable by the processing unit for:
• obtaining a shaft speed for a first engine of the multi-engine rotorcraft and a rotor speed for the at least one rotor;
• comparing the shaft speed to the rotor speed;
• when the shaft speed is greater than the rotor speed, detecting a first fault in the speed sensing system and issuing a first speed sensing system fault signal;
• and
• when the shaft speed is less than the rotor speed:
• determining whether the first engine is coupled to the at least one rotor based on a fuel flow to the first engine;
• detecting a second fault in the speed sensing system and issuing a second speed sensing system fault signal responsive to determining that the first engine is coupled to the at least one rotor;
• and
• controlling the multi-engine rotorcraft according to the first speed sensing system fault signal or the second speed sensing system fault signal.