In-line oil debris monitor for aircraft engine condition assessment

The development of an in-line, full flow oil debris sensor for aircraft engine condition assessment is described. First used on the F22 fighter, this sensor is the only "all-metals" debris detector in production. The sensor is based on an inductive measurement technique which enables the system to detect, count and classify wear metal particles by size and type (ferromagnetic and nonferromagnetic) above a minimum particle size threshold. In flight, the measured count values are compared to preset levels to provide prognostic health information on the oil-wetted components of the engine. This paper describes the sensor design requirements, principle of operation, electronic design and mechanical design features. The results of a test program established to correlate the oil borne debris measurements to component degradation characteristics and data from actual engine bearing failures, are also presented.