Evaluation Procedure (Cont)

NAVAIR 17-15-50.4

TM 38-301-4

T.O. 33-1-37-4

CGTO 33-1-37-4

Trend values included in the evaluation criteria tables, are, as previously stated, intended as

guidelines for the evaluator, since there are many other factors that must be evaluated to determine actual

equipment condition and whether subsequent laboratory recommendations to the customer are required.

Generally speaking, trends encountered will fall into one of the following categories:

(1) Level (little or no change): considered normal.

(2) Slightly to moderately increasing or decreasing within trend limits: Usually indicative of problems.

A sudden increase may indicate the start of an equipment problem, while a sudden decrease may indicate

defective sampling procedures, oil addition/change without documentation, or sample identification problems.

Investigation for causes or requests for verification samples and/or decreased sampling interval may be

appropriate.

(3) Sharply increasing or decreasing within trend limits: Usually indicative of problems. A sudden

increase may indicate the start of an equipment problem, while a sudden decrease may indicate defective

sampling procedures, oil addition/change without documentation, or sample identification problems. Investigation

for causes or requests for verification samples and/or decreased sampling interval may be appropriate.

(4) Erratic increases and decreases of trend level: This usually indicates a problem in sampling

procedure, oil addition or change without documentation, sample identification, etc. This should trigger a request

to review activity sampling procedures and submit a verification sample.

(5) Increases exceeding trend limits: Generally indicative of equipment problems. Consult comment

sections and equipment history. This will normally result in resample request and/or a maintenance action

recommendation.

NOTE

The above categories are subjective since no definitive increase/decrease point value

within the trend limits may be arbitrarily assigned. Severity of increase or decreases

must be determined by each evaluator after considering all factors involved. The above

listing is not considered complete but is provided to show that trend variances, while

still within limits, should be monitored to detect impending problems prior to

development, whether action recommendations to operating activities are required or

not.

Determine the appropriate recommendation to be made to the operating activity. Laboratory

recommendation codes applicable to nonaeronautical equipment are contained in Appendix A. The majority of

sample results will be normal, with the appropriate recommendation Code A. In most cases, this recommendation

may be determined without extensive reference to the tables or charts. However, applicable tables and charts for

the equipment being monitored should be consulted for any special guidance information.

If a recommendation for maintenance action is indicated, the comments sections and equipment

diagrams should be reviewed. These may provide additional maintenance information concerning likely problem

areas that may warrant inclusion in the laboratory recommendation/maintenance advisory notification to the

operating activity.

The above procedure can serve as a step-by-step operational guide for evaluator personnel with

limited experience, while retaining considerable flexibility for use by an experienced evaluator who can readily

take into account the many factors which influence evaluations and recommendations. The judgement of the

evaluator is an important part of the evaluation process. Judgement and experience shall not be subordinated by

numerical data when reasonable doubt exists in the validity of the recommendation indicated by the numerical

data.

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