What is a hung start in an engine?

A hung start refers to a situation in which the engine ignites, but it fails to accelerate to its self-sustaining RPM. This condition often occurs due to various factors such as insufficient fuel flow, inadequate airflow, or issues within the ignition system that prevent the engine from building the necessary speed to sustain combustion. In the context of aviation engines, achieving a self-sustaining RPM is critical for the engine to operate independently of external starting aids. If the engine cannot reach this threshold, it indicates a malfunction or failure in the starting process. It is essential for pilots and maintenance crews to recognize and diagnose a hung start promptly to ensure safe operation and prevent any potential damage to the engine.