Preserving Your Engine During a Period of Inactivity

By Pratt & Whitney Customer Service

Originally published February 14, 2017 – Updated April 2, 2020

Note: During this challenging time, we are taking the necessary measures to reduce risks for our employees, customers, suppliers and partners. As you plan for potentially significant effects on your operations, we are working to ensure we have the appropriate measures in place to continue providing the support you need. We are also publishing a series of articles on Airtime with practical advice to help minimize the impact on our customers.

If you’re not using your aircraft’s engine for a while, we recommend taking several simple but effective steps to keep it in pristine condition while it’s sitting idle. The required level of preservation will depend on the expected period of inactivity – and we strongly advise you to consult your engine maintenance manual or your aircraft maintenance manual.

These manuals provide the necessary preservation procedures and, in some cases, the procedures for returning an engine to service when preservation was not possible or overlooked. If you have any questions please contact us; we’re at your disposal. Service Information Letters (SILs) also provide important information on your engine. Contact us to determine what SILs apply specifically to your engine(s). The complete library of our SILs can be found here. The ultimate goal is to minimize the risk of engine deterioration, which is why these procedures are included in the engine and aircraft maintenance manuals.

1. Preserving the Aircraft Engine Fuel System

During normal operation, contaminants such as humidity may be found in the fuel. When the engine is active on a regular basis, it’s generally not an issue, since the contaminants will flow down into the combustor and be consumed there.

It’s a different story if your aircraft engine is in storage for an extended time. Contaminants will settle in areas that could lead to corrosion of the fuel system components, which will adversely impact performance.

To avoid potential issues, you will find the necessary steps to perform in your engine maintenance manual. For example, these will include items such as disconnecting the fuel line, purging the existing fuel and replacing it with preservation fluid. Please note that preservation fluid may be left in the engine as long as it’s inactive.

2. Preserving the Oil System of an Aircraft in Storage

Sometimes oil and water do mix. The oil used in an engine’s lubrication system is slightly hydroscopic—meaning it has the ability to absorb water. Since the oil system is not completely enclosed, air and oil will interact, and if the air is humid, the oil will extract water from it, become slightly acidic and slowly eat away at components and casings.

To prevent this, we refer you once again to the engine maintenance manual which will include instructions to preserve the oil system. For example, there will be instructions on how to remove all the oil from the engine prior to storing it.

3. Preserving the Entire Engine

When your engine’s going to be unused for some time, avoid condensation—which leads to rust. Keep it in a dry environment where there are no major temperature swings.

Storing the engine inside a hangar may not be sufficient since the temperature could fluctuate when the doors open and close or in cold weather conditions. To protect the engine, we recommend placing desiccant bags in it and sealing off all its openings. You could also remove the engine from the aircraft and put it in a vacuum-sealed bag with desiccant bags inside. In either case, you should monitor the humidity level inside the bag or engine using an indicator that will alert you by changing color.

No matter what kind of engine you have, moisture is your enemy. Materials like steel and magnesium are vulnerable to corrosion from water. If you protect the whole engine with no fuel or oil in it, you can keep it in serviceable condition until you’re ready to use it again.


Desalination Wash

Before storing your engine, perform a desalination wash to eliminate another corrosive: salt.