What happens during N2 Stagnation?

During N2 stagnation, the essential feature is that the initial light-off occurs, indicating that combustion is starting. However, as stagnation sets in, the spooling of the engine decelerates, which means that the rotational speed of the engine is not increasing as expected or may even decrease. This situation can occur due to various reasons, including issues with fuel flow or mechanical constraints within the engine.

This understanding of N2 stagnation is crucial because recognizing the symptoms, such as the initial light-off followed by a deceleration of spool speed, helps pilots and technicians diagnose engine performance issues or respond appropriately during abnormal operating conditions. The concepts of N2 speed and the performance of the engine components are vital for operational safety and effective troubleshooting in jet engines.