3.8.
MAINTENANCE PROCEDURES
It is important to see that the engine compartment is kept as
clean as possible because the highvelocity airflow through the
engine will draw any foreign objects into the compressor. All loose
parts, such as safety wire, cotter pin clippings, and nuts and bolts
should be removed immediately. Tubing and lines should be checked
for security, nicks, chafing, dents, and leaks.
Inspection and maintenance of gasturbine engines are somewhat
easier than those of reciprocating engines because the gas turbines
stay cleaner. Besides, the first several stages of most compressors
can be inspected for FOD by using a strong light. Also, the last two
turbine stages are readily opened for inspection of heat damage.
The oil system is checked on the daily inspection for proper
oil level. However, when adding oil, different types should not be
mixed. In the past the Army has used MILL7808 lubricating oil in
turbine engines. Because of the higher operating temperatures
encountered in the current gas turbine engines, a new oil has been
developed. Military Specification No. MILL23699 uses a new
synthetic base and new additive combination to cope with the more
severe operating conditions and higher temperature ratings. When
changing from MILL7808 to MILL23699 lubricating oil, check the
engine TM for proper procedures.
3.9.
CLEANING ENGINE ASSEMBLY
The exterior of the engine, and its attached components, can
be cleaned with a suitable cleaning solvent, such as PD680. If the
solvent is sprayed on the engine with compressed air, care must be
taken to avoid forcing dirt, solvent, or moisture into engine
openings and electrical connections. The primary purpose of cleaning
is to remove contaminants that might conceal minor cracks and defects
which if not detected could eventually lead to failure. Under normal
circumstances, engine components are cleaned only as necessary to
perform required inspection and repair. After using alternate or
emergency fuels, cleaning internal hotend parts may be required to
remove lead oxide deposits. These deposits, if not removed, are
detrimental to engine life and performance. The choice of any
particular cleaning agent or process depends upon the engine part to
be cleaned and the contaminants to be removed.
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