What is the maximum APU ITT for starting the engine for 1 second?

The maximum APU ITT (Interstage Turbine Temperature) for starting the engine for a duration of 1 second is 1050°C. This threshold is critical as it ensures that the engine is receiving sufficient energy to initiate the combustion process while protecting the APU and engine components from overheating and potential damage. Starting the engine is a sensitive operation where parameters like ITT must be monitored closely to maintain operational integrity and adhere to safety standards.

In this scenario, the specified temperature of 1050°C reflects the operational limits defined by the manufacturer for safe and effective engine start-up, and exceeding this limit could lead to significant mechanical failures or reduced lifespan of the components involved. The other temperature options do not meet the maximum threshold specified for safe engine starting operations, which is why they are not the correct selection.