During periods of aircraft down time including overhaul and temporary storage, aircraft engines require a number of preservative actions to maintain them ready for use. The processes involved in this vary by aircraft and engine manufacturer, so it is important to consult the relevant technical authority before taking any steps.
Aircraft operators can perform an engine run-up once a week.
Application of AeroShell Fluid 12.
AeroShell Fluid 12 is a low-volatility synthetic ester oil with various applications across the aircraft including general lubrication and aircraft instruments. It is approved to MIL-PRF-6085E and AIR 3511/A, referenced under NATO O-147, and equivalent to DEF STAN 91-49 and Joint Services Designation OX-14.
SNECMA (Safran Aircraft Engines) detail the process of draining and refilling the engine with AeroShell Turbine Engine Oil and 5% of AeroShell Fluid 12 as a turbine preservative. This is additionally referenced in the Airbus CML under CP 5067.
GE Aviation direct users to apply this product as a concentrate into the engine to preserve turbine bearings. As AeroShell Fluid 12 is a synthetic ester, there is no need to flush it out before use with turbine engine oil.
Incorporation of speciality preservative turbine engine oils.
AeroShell Turbine Engine Oil 2 and AeroShell Turbine Engine Oil 3 are traditional mineral based turbine engine oils developed in the 1950’s.
AeroShell Turbine Engine Oil 2 is a 2 mm2/s oil with a pour-point depressant and an anti-oxidant added. It is approved to MIL-PRF-6081E Grade 1010, and is referenced under NATO O-133 and Joint Service Designation OM-10 (obsolete).
AeroShell Turbine Engine Oil 3 is a 3 mm2/s oil with an anti-corrosive additive added. This oil meets DEF STAN 91-99, and is referenced under NATO O-135 and Joint Service Designation OM-11.
Both of these oils are widely used to inhibit fuel systems and fuel system components during storage. Flushing a drained fuel system with one of these oils leaves a protective film of oil on the walls of the fuel system which acts as a corrosion inhibitor during storage before the engine goes into operation. There is no need to flush these oils out of the system before engine run-up.
Please note, this process can only happen when the engine has been removed from the aircraft.