Which condition is most critical to monitor during start-up once fuel flow has begun in a turbine engine?

Monitoring EGT (Exhaust Gas Temperature), TIT (Turbine Inlet Temperature), or ITT (Interstage Turbine Temperature) during the start-up phase of a turbine engine is critical because these parameters directly indicate the engine’s thermal condition and performance. Once fuel flow has commenced, the ignition process initiates, leading to combustion in the engine. High temperatures in the exhaust or turbine inlet can signal excessive heat that may indicate abnormal engine behavior, potentially leading to damage or failure.

Monitoring these temperature readings helps ensure that the engine operates within safe limits throughout the start-up process. If these temperatures rise too quickly or exceed defined limits, it can lead to engine damage, making them vital indicators of a properly functioning engine.

The other parameters, while also important, do not provide as immediate and critical information regarding the engine's thermal state at the onset of fuel flow. RPM focuses on the engine speed, which, though relevant, does not reflect the immediate combustion and thermal performance as closely as the temperature readings do. Fuel pressure is important for ensuring adequate fuel delivery, while oil temperature is necessary for engine health but is not as crucial during the specific phase of start-up when fuel flow begins. Thus, the focus on EGT, TIT, or IT