What is referred to as the speed (RPM or percent) of the low pressure compressor in a dual compressor engine?

In a dual compressor engine, the designation for the speed of the low-pressure compressor is referred to as N1. N1 typically indicates the rotational speed of the low-pressure compressor and the associated turbine, measuring it in either RPM (revolutions per minute) or as a percentage of a given maximum speed. This parameter is crucial for assessing engine performance and operational conditions, as it directly influences thrust and fuel efficiency during various phases of flight.

Understanding the significance of N1 is essential for flight engineers who monitor engine performance. This value helps in ensuring that the engine operates within safe limits and contributes to effective performance management. The other designators, such as N2, usually pertain to the high-pressure compressor speed, and do not represent the low-pressure compressor speed, making N1 the correct identification in this case.