Inspection of Stored Aircraft Engines

Most maintenance shops provide a scheduled inspection system for engines in storage. Normally, the humidity indicators on engines stored in shipping cases are inspected every 30 days. When the protective envelope must be opened to inspect the humidity indicator, the inspection period may be extended to once every 90 days, if local conditions permit. The humidity indicator of a metal container is inspected every 180 days under normal conditions.

If the humidity indicator in a wooden shipping case shows by its color that more than 30 percent relative humidity is present in the air around the engine, all desiccants should be replaced. If more than half the dehydrator plugs installed in the spark plug holes indicate the presence of excessive moisture, the interior of the cylinders should be resprayed. If the humidity indicator in a metal container gives a safe blue indication, but air pressure has dropped below 1 psi, the container needs only to be brought to the proper pressure with dehydrated air. However, if the humidity indicator shows an unsafe (pink) condition, the engine should be represerved.