What are the two methods of performing compressor washes?

• A. While motoring the engine with starter only
• B. While motoring the engine with starter only; While running the engine
• C. While the engine is off
• D. Only at flight idle

Answer: (B)

Compressor wash works by circulating cleaning fluid through the compressor while the rotor is turning, so the fluid can reach the blades and flush out deposits.

The two practical methods are: first, motoring the engine with the starter only, which spins the compressor without ignition or fuel and allows the wash fluid to be pumped through safely; second, washing while the engine is running, using the engine’s airflow to distribute the cleaner and flush debris out of the compressor. These two cover safe, effective ways to circulate the wash fluid under rotation.

Washing with the engine off isn’t one of the standard two methods because there’s no rotation to drive the fluid through the compressor, making cleaning less effective.