Improving Commercial Airliner Hydraulic System Reliability

This technical report presents research on enhancing the reliability of commercial airliner hydraulic systems through effective contamination control. It outlines the detrimental effects of fluid contamination on machinery performance and longevity, emphasizing the need for clean fluids and fine filtration. The report discusses various contamination mechanisms, including abrasive wear, fatigue wear, stiction, silting, erosion, and the impact of water and solvent contamination. It recommends a target cleanliness level of NAS 1638 Class 3 for commercial airlines and details how this level can be achieved using modern contamination control methods, such as fine filters and on-line particle counting. The report also reviews studies conducted over two decades, illustrating the relationship between filtration efficiency and wear in hydraulic components, particularly in pumps and servovalves. The findings underscore the importance of maintaining fluid cleanliness to improve mean time between failures (MTBF) and overall system reliability in aviation hydraulics.