Corrosion can be a devastating enemy of aircraft engines, particularly those in planes that are flown infrequently or placed in storage for an extended period.
New engines or those with new or freshly honed cylinders after a top or major overhaul are of particular concern. In areas of high humidity, these have been instances where corrosion has been found in such cylinders after an inactive period of only a few days. Once these cylinders have been operated for approximately 50 hours, the varnish that collects on the cylinder walls offers some protection against this happening.
However, proper steps must be taken to preclude the possibility of corrosion at any time. Adequate storage is especially important if the aircraft is based near the seacoast or in areas of high humidity and is not flown more than once a week.
The best method for preventing corrosion of the cylinders and other internal parts of the engine is to fly the aircraft at least once a week, long enough for the engine to reach normal operating temperatures that will cook out moisture and other by-products of combustion.
General
There is no practical procedure that will ensure corrosion prevention on installed aircraft engines. Susceptibility to corrosion is influenced by geographical location, season, and usage. The owner/operator is responsible for recognizing the conditions that are conducive to corrosion and take appropriate precautions.
Engine Preservation
Corrosive can occur in engines that are flown only occasionally regardless of geographical location. In coastal areas and areas of high humidity, the corrosive attack can occur in as little as two days. The best method of reducing the likelihood of a corrosive attack is to fly the aircraft at least once every week for a minimum of our hour.
Note: Corrosive attacks may reduce engine service life. Of primary concern are cylinders, piston rings, valves, valve guide, camshaft, and lifters.
Temporary Storage (Aircraft that are not flown for 30 to 90 days)
Preparation for Storage
- Remove oil sump drain plug and drain oil. Replace drain plug, torque, and safety. Remove oil filter, install new oil filter, torque, and safety. Service engine to proper sump capacity with oil conforming to MIL-C-6529 Type II
- Perform a ground run-up. Perform a pre-flight inspection and correct any discrepancies. Fly the aircraft for one hour at normal operating temperatures.
Note: If the engine is not returned to flyable status on or before the 90-day expiration, it must be preserved by “Indefinite Storage” procedures.
Indefinite Storage (Aircraft that are not flown for 90 days)
Preparation for Storage
- Remove oil sump drain plug and drain oil. Replace drain plug, torque, and safety. Remove oil filter, install new oil filter torque and safety—service engine to proper sump capacity with oil conforming to MIL-C-6529 Type II.
- Perform a ground run-up. Perform a pre-flight inspection and correct any discrepancies. Fly the aircraft for one hour at normal operating temperatures.
Long-Term Storage (Aircraft that are not flown for over 120 days)
Follow recommendations from Continental Aerospace Technologies
For more information on aircraft values or appraisals, please contact Jason Zilberbrand, [email protected]
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