What action should be done immediately if the start sequence ITT approaches the limit?

When the start sequence Interstage Turbine Temperature (ITT) approaches its limit, the immediate action that should be taken is to shut off the fuel. This is crucial because if the ITT exceeds the maximum allowable temperature, it could lead to serious engine damage or failure. Shutting off the fuel halts the combustion process quickly, allowing the engine to cool down and preventing potential catastrophic failure.

Monitoring cockpit instruments, though important for overall situational awareness, does not actively address the imminent risk posed by an approaching ITT limit. Increasing throttle could exacerbate the situation by increasing fuel flow and thus further elevating the ITT. Consulting the flight manual is useful for reference and guidance on procedures, but in a critical situation where the ITT is nearing limits, immediate action is required rather than delaying for manual verification.