Ambient temperature variation aircraft hydraulic systems have to withstand can be nearly 90 deg C. Besides of the ambient temperature the hydraulic systems have to withstand very high variation in system temperature. Due to small fluid volume, limited heat exchanger capacity and high system peak power these systems usually run exceptionally hot and fluid may have to withstand a temperature variation as high as nearly 180 deg C. Violent ambient conditions and extreme conditions in the system itself cause hydraulic fluid to be under very exceptional stress in comparison to typical mobile hydraulic systems. Also hydraulic system maintenance and servicing practices in aircraft differ a great deal from practices used in other mobile hydraulic systems. Fluid contamination and deterioration are normal consequences of the system operation and ambient conditions. Performance, lifetime and reliability of hydraulic components are very sensitive to the quality of the hydraulic fluid used in the system and thus is of great importance to know the overall quality of the fluid in the system and to understand how the quality is affected by maintenance and servicing. This paper presents results of the fluid quality monitoring study made in two different types of aircraft using different types of hydraulic fluid (mineral oil based and synthetic hydrocarbon). Four individual aircrafts were selected for research and fluid from each aircraft was sampled periodically. Typical parameters describing the fluid quality (TAN, viscosity, water content etc.) were analysed from samples. Also the level of particulate contamination was determined. Results give an explanation to many typical problems encountered in aircraft hydraulic systems and also point out short comings of typical maintenance servicing procedures used in aircraft hydraulics.
Hydraulic fluid quality in aircraft hydraulic systems
2007
13 Seiten, 11 Bilder, 1 Quelle
Aufsatz (Konferenz)
Englisch
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