RELIABILITY ANALYSIS OF THE 4.5 ROLLER BEARING

by
Cole Muller
June 2003

ABSTRACT

The J-52 engine used in the EA-6B Prowler has been found to have a faulty

design which has led to in-flight engine failures due to the degradation of the 4.5 roller

bearing. Because of cost constraints, the Navy developed a policy of maintaining rather

than replacing the faulty engine with a re-designed engine. With an increase in Prowler

crashes related to the failure of this bearing, the Navy has begun to re-evaluate this

policy. This thesis analyzed the problem using methods in reliability statistics to develop

policy recommendations for the Navy.

One method analyzed the individual times to failure of the bearings and fit the

data to a known distribution. Using this distribution, we estimated lower confidence

bounds for the time which 0.0001% of the bearings are expected to fail, finding it was

below fifty hours. Such calculations can be used to form maintenance and replacement

policies.

Another approach analyzed oil samples taken from the J-52 engine. The oil

samples contain particles of different metals that compose the 4.5 roller bearing. Linear

regression, classification and regression trees, and discriminant analysis were used to

determine that molybdenum and vanadium levels are good indicators of when a bearing

is near failure.

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