What speed should the GTG maintain while motoring the RIMMS?

• A. Greater than 3000 RPM
• B. Less than 2000 RPM
• C. Between 2000 and 4000 RPM
• D. 0 RPM

Answer: (B)

When you motor the GTG, you’re turning the turbine shaft with an external drive without firing the engine. The goal is to pre-spin and circulate oil, check for mechanical clearance, and verify systems like the RIMMS respond, all without putting the unit into full operation. Because there’s no combustion to regulate the rotor, you keep the speed very low to avoid overspeed and excessive bearing loads. Maintaining less than 2,000 RPM provides a safe, controlled speed that allows lubrication and system checks to occur without stressing the turbine or its components. Going higher risks exceeding safe limits and potential damage, while keeping it at zero wouldn’t accomplish the necessary pre-spin checks.