ITT must be below what value before attempting a ground start?

• A. 120
• B. 100
• C. 110
• D. 130

Answer: (A)

Inter-Turbine Temperature (ITT) is the temperature the turbine experiences during start, and it’s a key safeguard against overheating as the engine spools up. Before light-off, ITT must be below a safe threshold so that when fuel is introduced and ignition begins, the turbine won’t see an excessive temperature surge. If ITT is already too high, the rapid rise during start could push turbine temperatures past what the blades and seals can tolerate, risking damage.

The standard threshold used for a safe ground start is 120°C. This value provides a practical balance: low enough to protect the turbine during the initial light-off, but not so low that starts are unnecessarily delayed. Lower thresholds would unduly delay starts, while higher thresholds could allow overheating risks during startup.