During the engine rinse, the decrease in N1 must not exceed what percent, and TOT must decrease by at least how many °C?

During the engine rinse, the decrease in N1 must not exceed what percent, and TOT must decrease by at least how many °C?

• A. 10%, 25°C
• B. 5%, 15°C
• C. 15%, 30°C
• D. 20%, 20°C

Answer: (A)

During an engine rinse you’re aiming for a controlled, safe response from the engine. The N1 drop must be limited because a large decrease signals a sudden load change that can cause instability, surge, or flameout as the purge flow is introduced. Keeping the N1 decrease to no more than 10% ensures the rotor speed stays within a stable range while the rinse is performed. At the same time, the turbine outlet temperature (TOT) should fall by at least 25°C to show the engine is actually cooling and that the rinse flow is effectively circulating through the system. If TOT doesn’t drop that much, the purge may not be achieving the intended cooling and cleaning effect. So the combination of a maximum 10% N1 decrease and a minimum 25°C TOT decrease represents the safe, effective limits for performing the engine rinse.

During an engine rinse you’re aiming for a controlled, safe response from the engine. The N1 drop must be limited because a large decrease signals a sudden load change that can cause instability, surge, or flameout as the purge flow is introduced. Keeping the N1 decrease to no more than 10% ensures the rotor speed stays within a stable range while the rinse is performed. At the same time, the turbine outlet temperature (TOT) should fall by at least 25°C to show the engine is actually cooling and that the rinse flow is effectively circulating through the system. If TOT doesn’t drop that much, the purge may not be achieving the intended cooling and cleaning effect. So the combination of a maximum 10% N1 decrease and a minimum 25°C TOT decrease represents the safe, effective limits for performing the engine rinse.