Thursday, November 15, 2012

Piston Engine Oil & Filter Element - Inspection

                 CASA issued AIRWORTHINESS BULLETIN Piston Engine Oil & Filter Element - Inspection AWB 85-013 Issue : 1 Date : 14 November 2012
                     Applicability : All aircraft piston engines - particularly those equipped with “disposable” or “spin-on” oil filtration “paper” element cartridges.
                       Purpose : Advise all aircraft owners, operators and maintenance personnel to cut open the canister of disposable oil filters and examine the element and to emphasise the importance of thorough oil filter element inspections and proper evaluation of filter debris to assist in the determination of engine serviceability and need for corrective action.
                            Clean engine oil is fundamental to engine durability and reliability in operation. The engine oil system cools, reduces friction between moving parts and flushes potentially harmful wear particles away from contacting surfaces as it circulates through the engine. As it does so, the oil becomes increasingly contaminated. The engine oil filters help reduce wear by collecting these harmful particles from the oil.
                             Many light aircraft piston engines are equipped with simple oil screens – usually a fairly coarse mesh screen on the suction side of the oil pump and a much larger and finer screen on the pressure side of the oil pump. Micronic paper “spin-on” filter elements have proved quite effective in maintaining cleaner oil via much improved oil filtration and the increased ability to provide early clues to the internal health of the engine - and of impending failure.

                            Many SDRs received by CASA demonstrate that a potential in-flight engine failure has been avoided by early detection of adverse internal wear or damage by careful examination of the oil and oil filter contents. Recent reports, however, indicate that some operators/maintainers may be either failing to look for metal debris in the screens and filter, or failing to properly evaluate what was found at the oil filter inspection immediately prior to catastrophic engine failure.
                      In addition to regular oil filter analysis, some manufacturers recommend that operators use spectrographic means to analyse the oil to monitor trends in minute levels of brass, bronze, aluminium, steel and silicone, etc. Whilst particulate in the sub-microscopic to microscopic range is undetectable during a visual inspection of the filter element contents, this analysis method is a valuable tool for monitoring the health of piston engines where available.

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