What should be done if a hung start occurs during the starting of a turbine powerplant using a compressed air starter?

In the event of a hung start during the starting of a turbine powerplant with a compressed air starter, the appropriate action is to shut down the engine. A hung start occurs when the engine fails to achieve the required speed, typically due to insufficient fuel flow, airflow issues, or starter performance problems. Continuing the start sequence could lead to possible damage or unsafe conditions, as the engine may not be functioning correctly, risking a complete failure or other safety issues.

Shutting down the engine is crucial to prevent further complications and allows for troubleshooting to identify the root cause of the hung start. This response is in line with safety protocols, ensuring that the situation is manageable and prevents any exacerbation of the problem. It also allows for steps to be taken to rectify the malfunction before attempting another start.

The options involving continuing the start sequence or increasing starter air pressure could potentially worsen the situation, as they do not address the underlying issues leading to the hung start. Similarly, activating the backup ignition system might not resolve the problem if the engine is not reaching the required speed for ignition or if conditions affecting combustion are not remedied. Thus, shutting down the engine is the most responsible and safe action to take in this scenario.