Which statement best explains why ITT is used for start/run limits and EGT for exhaust health?

• A. ITT measures overall exhaust health while EGT controls start limits
• B. ITT is measured in hot section for limits; EGT in exhaust for health monitoring
• C. ITT and EGT both indicate start/run limits
• D. ITT is used for oil condition while EGT monitors ambient temperature

Answer: (B)

During starting and running, the hot section is where the risk of thermal overstress is greatest, since fuel flow drives a rapid rise in temperature there. Inter-Turbine Temperature (ITT) is measured in that hot region and provides a direct indication of the maximum temperature the turbine components will experience. Setting limits on ITT gives immediate protection against overheating during start and spool-up.

Exhaust Gas Temperature (EGT), measured after the turbine in the exhaust, serves as a health indicator for the engine. It reflects how well the combustor and turbine are operating overall—changes in efficiency, component wear, or cooling can shift the exhaust temperature. Monitoring EGT over time helps detect degradation or anomalies and guides maintenance before a failure occurs, rather than acting as a protective limit during start/run.

So ITT is used to enforce safe limits in the hot section, while EGT is used to monitor exhaust health and overall engine condition.