How does the cockpit receive the NG signal?

How does the cockpit receive the NG signal?

• A. From the cockpit electrical bus
• B. From the NP winding of the alternator
• C. From the NG winding of the alternator
• D. From the engine fuel flow sensor

Answer: (C)

The cockpit receives the Ng signal from the NG winding of the alternator. The gas generator speed (Ng) is the engine speed that directly drives the compressor and determines how fast the engine is producing air and power. The alternator is driven by the engine, so a dedicated winding on the alternator (the Ng winding) generates a voltage that is proportional to Ng. This signal is conditioned and routed to the cockpit instruments, providing a real-time Ng readout for engine monitoring and FADEC/engine control. This is the best source because it is a direct, engine-driven measurement of gas generator speed. The NP winding would track the power turbine speed, which is a different parameter, so it isn’t what the cockpit uses for Ng. A fuel flow sensor measures fuel consumption, not rotor speed, and the cockpit electrical bus is a power supply, not a signal source.

The cockpit receives the Ng signal from the NG winding of the alternator. The gas generator speed (Ng) is the engine speed that directly drives the compressor and determines how fast the engine is producing air and power. The alternator is driven by the engine, so a dedicated winding on the alternator (the Ng winding) generates a voltage that is proportional to Ng. This signal is conditioned and routed to the cockpit instruments, providing a real-time Ng readout for engine monitoring and FADEC/engine control.

This is the best source because it is a direct, engine-driven measurement of gas generator speed. The NP winding would track the power turbine speed, which is a different parameter, so it isn’t what the cockpit uses for Ng. A fuel flow sensor measures fuel consumption, not rotor speed, and the cockpit electrical bus is a power supply, not a signal source.