What is the most critical instrument to monitor after fuel flow begins when starting a turbine engine?

Monitoring the exhaust gas temperature (EGT), turbine inlet temperature (TIT), or interstage turbine temperature (ITT) gauge is crucial after fuel flow begins when starting a turbine engine because these gauges provide immediate feedback on the health and performance of the engine during the critical phases of startup.

Once fuel is introduced into the combustion chamber, it is essential to ensure that the engine is operating within safe temperature limits. High temperatures can indicate potential issues such as abnormal combustion or engine-related failures, risking damage to the turbine components. Maintaining these temperatures within acceptable ranges is vital to prevent overheating and possible engine failure.

While the fuel flow gauge provides information about the amount of fuel being delivered to the engine, and the oil pressure gauge monitors system health and lubrication, they don’t offer the immediate insight into combustion stability or performance that the EGT, TIT, or ITT instruments do during the startup phase. An altitude gauge is unrelated to engine performance and does not provide relevant information during this critical time. Thus, the temperature gauges are the most critical for assessing the initial operational safety and performance of the engine.