Section II: AERONAUTICAL EQUIPMENT WEAR METAL ANALYTICAL METHODOLOGY

NAVAIR 17-15-50.3

TM 38-301-3

T.O. 33-1-37-3

CGTO 33-1-37-3

SECTION II

AERONAUTICAL EQUIPMENT

WEAR METAL ANALYTICAL METHODOLOGY

2-1. METHODOLOGY. The JOAP aeronautical wear-metal analytical methodology encompasses the

interpretation of used oil sample analysis results, assessment of equipment condition based on the analysis

results, diagnosis of the probable source (s) of the wear metal(s), and the issuance of accurate and effective

equipment maintenance and/or operational recommendations to the operating activity. This methodology has the

potential to standardize evaluator responses and to result in more accurate evaluation criteria and laboratory

recommendations.

a. The aeronautical equipment wear-metal analytical methodology uses three separate but interrelated

sets of tables:

(1) Wearmetal Evaluation Criteria Tables arranged by type equipment and end item (Appendix A).

These tables provide wear-metal range and trend values which relate the oil sample wear-metal concentration to

the expected condition of the equipment and/or the oil condition.

(2) Supplemental Diagnostic Guidance Tables (Appendix A). These tables provide addiitional wear-

metal diagnostic guidance for each type of equipment being evaluated to assist in identifying the most probable

failing part of the equipment (source of the wearmetal) when wearmetals are present, singly or in combinations, at

other than normal concentrations in the sample or when an abnormal trend is evident. Boxes are placed around

elements that will be the primary indicators of a particular failing component.

(3) Decision Making Guidance Table (Table 2-2) which provides guidelines for the evaluator

concerning appropriate recommendations that should be issued after the sample is analyzed.

(4) Appendix B contains a list of current service equipment not enrolled in the JOAP program.

b. Normally, separate Evaluation Criteria and Diagnostic Guidance Tables are provided for each type of

equipment but some tables are combined for different series engines on the same or similar end items. Separate

tables are usually required because of differences in the normal sampling intervals, equipment operating

characteristics, mission profiles and observed operating times required for wear-metal concentrations to

progress from normal to abnormal. These characteristics were combined to produce data used to establish wear

metal ranges and trends. When possible, information compiled from JOAP detected failures was used to

establish the abnormal wear metal concentration. When this was not possible, the abnormal wear metal

concentration was established using accepted statistical methods. The concentration ranges and trend values

are continually analyzed and adjusted as required, using historical information, engineering reviews, and

equipment teardown results. The sampling intervals, wearmetal range limits, and trend values were established

to reduce the possibility that the wear-metal concentration may go from normal to abnormal without a sample

being taken. The concept is one of increased surveillance by more frequent sampling as the wear

concentrations increase. Information is provided on abnormal trend values because rapid metal-wear increases,

even at low concentrations and within acceptable range limits, may be indicators of impending failure. Activities

identifying a requirement to modify these tables for specific equipment should contact the cognizant engineering

authority for the equipment involved.

c. If the necessity for making a maintenance recommendation is established, the Supplemental Diagnostic

Guidance Tables may then be used to pinpoint possible problem areas and to help identify a specific

recommendation. In many cases it is possible to give maintenance personnel an indication of what components

in the equipment are wearing abnormally, based on the wear metals being produced.

2-1