Hot Start & Hung Start | Abnormal start of Turbine Engine

Starting Turbofan, Turboprop Engines or Turbine Engine

The starting techniques for turbine engines vary widely, and no attempt should be made to use these procedures for the actual starting of an engine. Check with the detailed procedures given within the respective manufacturer's instructions or their approved equivalent manuals when starting all turbine engines.

Any turbine engine is started by these common three steps in the correct sequence and time with proper monitoring.

The engine starter turns the main compressor at adequate speed to supply sufficient airflow through the engine & provides enough airflow to the combustion chamber, and then the igniters are turned on and provide a hot spark to light the fuel air mixture. When the engine accelerates and reaches a self-sustaining speed, the starter is disengaged.

Turbine/Jet Engine abnormal Start

The turbine engine may fails to start or abnormal start. Some common problems are as under:

The Engine Fails to Start

The engine may fail to start out within the specified time due to lack or absence of fuel in the engine, insufficient or no proper electrical power to the exciter in the ignition circuit/system, or an inappropriate fuel mixture. If the engine doesn't start within the given time, shut it off. Fuel and ignition must be shut off in all cases of unsatisfactory starts. To eliminate collected fuel from the engine, keep rotating the compressor for around 15 seconds. Allow a 30-second fuel draining period before attempting to start the engine again.

Hot Start

When the engine starts but the exhaust gas temperature exceeds the desired limits, this can be known as a hot start. As we know, the TIT/EGT is the most significant factor to be monitored, and it's kept to the required limit. If the EGT limit is exceed, the turbine engine may be damage &  would require a costly repair. The reason for the hot start is a very rich fuel/air mixture entering the combustion chamber, which produces an extremely hot temperature. Either an excessive amount of fuel or insufficient airflow might trigger this problem. The engine's fuel supply must be shutoff off quickly in the case of a Hot Start.

Hung or False Start

False or Hung start occurs in gas turbine engine when it starts normally but the compressor rpm remains low instead of increasing to the regular starting rpm. Inadequate starting torque or the starter cutting off before the engine starts to self-accelerate are two common causes for hung start of a turbine engine. In the case of Hung start, shut down the engine immediately and diagnose the cause before the next start.

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