How is a hot start indicated when starting a turbine engine?

A hot start in a turbine engine is indicated when the exhaust gas temperature exceeds specified limits during the start sequence. This happens when there is an excessive amount of fuel introduced into the combustion chamber before sufficient airflow is established, leading to an uncontrolled combustion process. As the engine starts, the temperature should ideally rise in a controlled manner; however, if the temperature rises too quickly or exceeds the maximum allowable limits, it signals that the engine is experiencing a hot start. This condition requires immediate attention to prevent potential damage to the engine components due to overheating.

The other indicators, such as not reaching idle speed, excessive vibration, or significant drops in fuel pressure, do not directly indicate a hot start condition. Idle speed failure could result from other mechanical issues, while vibration typically relates to imbalance or operational problems rather than temperature control. A drop in fuel pressure points to fuel delivery issues, which, while important, are not directly related to the hot start phenomenon itself. Therefore, monitoring exhaust gas temperature is critical during startup to ensure the engine remains within safe operating limits.