Method for Analyzing Lubricating Oil Contamination of Aircraft Systems

One potential source of cabin air contamination is lubricating oils used in the engines. Type II oils are required for the main engines, but Type I or Type II oils can be used for the APU, with Type I recommended by some engine manufacturers for its cold-start properties. Southwest Research Institutes (SwRI®) Department of Emissions Research used an internally developed analytical method called Direct Filter Injection/Gas Chromatograph (DFI/GC™) to analyze for volatile fractions of lubricating oil contaminants on Environmental Control System (ECS) components.

Samples of two standard Type II aviation turbine lubricating oils were analyzed with the DFI/GC™ method and their spectra examined. Sufficient differences were observed to clearly identify the oils. A sample of accumulated contaminant taken from a part of a failed ECS pack was analyzed and clearly identified as one of the two lubricating oils. An aircraft was set up with one oil in the main jet engines and the other oil in the Auxiliary Power Unit. When a problem occurred with the ECS pack, samples of deposits were analyzed from ECS pack components, and the lubricating oil contaminant source was clearly identified. Therefore, the DFI/GC method was shown to be very useful in identifying the source of oil contamination on ECS pack components. It is believed that the technique has similar usefulness in investigating oil contamination of a variety of aircraft components.