MIL-PRF-23699G
oil sample. The viscosity shall be determined in accordance with ASTM D445. The
total acid number shall be determined in accordance with SAE ARP5088.
4.4.16 Bearing corrosion (class C/I only).
The candidate oil shall successfully pass three
series of bearing corrosion tests:
a. The first series of tests shall be conducted on the candidate oil as received (new oil)
with a minimum of 18 of 36 bearing raceways being free from corrosion;
b. The second series shall be conducted on the post-test filtrate from the 204 °C.
Corrosion and oxidation stability test (stressed oil) (see table I) with a minimum of
three of six bearing raceways being free from corrosion.
c. The third series shall be run on the used oil from the turboshaft engine test (see 4.4.17)
with a minimum of three of six bearing raceways being free from corrosion.
d. Any batch of bearing corrosion tests shall also include one pass and one fail reference
oil test bearing for quality control purposes.
4.4.17 Turboshaft engine. The oil shall be subjected to an accelerated endurance test in a
turboshaft engine for a period sufficient to determine its performance characteristics. Engine
components shall be inspected for defects upon completion of the endurance test run. Any
defects found in the components of the engine which are serviced by the oil shall be cause for
disqualification. Engine test conditions and test period shall be specified by the activity
responsible for qualification (see 4.2).
4.4.18 Service evaluation. When candidate lubricants that were the result of unique or
unusual formulation or manufacturing technologies are submitted for qualification testing, the
qualification activity (see 4.2) may require additional engine and flight test evaluations. The
additional evaluations shall be conducted by the qualifying activity, or its designated
representative, and shall consist of the following:
a. Model type test. A 150-hour, test cell operated, evaluation shall be conducted on a
minimum of two different models of aviation gas turbine engines used by the U.S.
Military.
b. Flight evaluation. A 2000-hour flight evaluation shall be conducted in a Government
owned aircraft having the same engine model as used in the Model type test, above.
4.4.18.1 Evaluation criteria. The rating criteria for both the model type test and the flight
evaluation will be reported as satisfactory or unsatisfactory. The satisfactory rating is contingent
upon the successful completion of the test duration without a lubricant-related discrepancy and
the satisfactory condition of the lubricant-wetted parts upon post-test engine disassembly and
inspection. The post-test condition of the candidate lubricant shall be free of deleterious
features.
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