N1 and N2 express the rotational speed of turbine engines as a percentage of the maximum normal operating RPM. N1 is the speed of the low pressure spool and serves as the primary power setting, and N2 is the speed of the high pressure spool which indicates if aircraft systems have sufficient power.

What does N1 mean in aviation?

Description. In an axial flow jet engine, N1 refers to the rotational speed of the low speed spool which consists of the fan, the low pressure compressor and the low pressure turbine, all of which are connected by a concentric shaft.

The N2 Indicator is a cockpit gauge which, in most installations, presents the rotational speed of the high pressure (high speed) engine spool, a speed that is referred to as N2. In a three spool engine, such as the Rolls Royce RB211, N2 is an indication of the intermediate pressure spool.

What does N1 measure?

The N1 Indicator is a cockpit gauge which presents the rotational speed of the low pressure (low speed) engine spool, a speed that is referred to as N1. The gauge is usually calibrated in percent RPM based on an engine manufacturer defined rotational speed that corresponds to 100%.

Conceptually, N1 is the fan (or, fan speed) and is most related to your thrust (since the fan produces more thrust than the core on today’s big motors).