Condition monitoring of aircraft by quantitative filter debris analysis

Abstract

AbstractVarious condition monitoring techniques are used collectively to monitor the health of aircraft engines and transmission, a concept known as Integrated Health Monitoring (IHM). A well‐established quantitative technique is Aircraft Oil Analysis (AOA), in which spectroscopic techniques such as Rotating Disk Electrode Atomic Emission Spectroscopy (RDE‐AES) are employed to analyse periodic oil samples for wear debris. Usually, no sample preparation is undertaken, as the oil sample containing both dissolved and suspended metallic wear debris is analysed directly. AOA works well for oil‐lubricated systems with relatively coarse filtration that allow circulation of the debris and its subsequent abrasive contact with moving components. To avoid this secondary wear, finer filtration is employed on both new and older aircraft. Less wear debris, and thus information, is available in the oil. A technique that quantitatively analyses the wear debris caught on the filter has been developed and is termed Quantitative Filter Debris Analysis (QFDA).Actual oil filters from CF88 Challenger ALF 502L‐2C and Hornet F404 engines were obtained in sequence, when possible, prepared by the developed procedure, and analysed with AOA instrumentation. With sufficient results, both normal and abnormal levels of wear rates emerged, as has been recorded and used for AOA. Moreover, trending of the data for sequential samples has demonstrated the capability of GFDA for condition monitoring.