What is the maximum ITT allowed at engine start?

The maximum Inter-Turbine Temperature (ITT) allowed at engine start is set to protect the engine components from excessive thermal stress that can lead to damage or decreased performance. The value of 1000ºC for 5 seconds is an industry standard for many turbine engines during start-up phases, as it allows for a short period of increased temperature to accommodate the necessary combustion processes while still maintaining engine integrity.

This limit is defined to ensure that the engine can reach operational conditions without incurring excessive wear or risk of failure from overheating at start-up. By allowing this brief period of high temperature, the engine can effectively ignite and stabilize without exceeding limits that would affect its overall lifespan and reliability.

In contrast, other temperatures provided in the other choices, such as 850ºC for 5 minutes or 870ºC for 20 seconds, would impose stricter limitations on the start-up thermal envelope, which could potentially make the engine harder to start or lead to operational inconsistency in different environmental conditions. The option of 150ºC is not applicable for engine start parameters as it falls significantly below typical operational thresholds for turbine engines.