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This document discusses the relative merits of the physical and chemical properties of hydraulic fluids in relation to the aerospace hydraulic system design, and the related materials compatibility. The discussion in this report applies both to hydrocarbon and phosphate ester based aircraft hydraulic fluids. In some cases, numerical limits are suggested, but, in general, the significance and effect of a property is noted qualitatively.

This SAE Aerospace Recommended Practice (ARP) provides a procedure for obtaining filter patch test samples from the following types of aerospace non-rotating hydraulic equipment: Mechanical/Hydraulic Units Electro/Hydraulic Units Pneumatic/Hydraulic Units

This SAE Aerospace Information Report (AIR) discusses the design choices and engineering trade-offs available to the system designer in the efficient selection and application of Last-Chance filters in contrast to main or primary system filters.

This SAE Aerospace Recommended Practice (ARP) establishes a method for evaluating the particulate matter extracted from the working fluid of a hydraulic system or component using a membrane. The amount of particulate matter deposited on the membrane due to filtering a given quantity of fluid is visually compared against a standard membrane in order to provide an indication of the cleanliness level of the fluid. A particular feature of this method is the membrane preparation to achieve an even particulate distribution on the membrane suitable for other applications. Membrane evaluation using standard membranes, described in this document, is an alternative technique to counting with either an optical microscope (ARP598) or an automatic particle counter (ISO 11500). The latter particle counting procedures are considered more precise.

This SAE Aerospace Information Report (AIR) discusses the design choices and engineering trade-offs available to the system designer in the efficient selection and application of Last-Chance filters in contrast to main or primary system filters.

The purpose of this test procedure is to present test methods that can be utilized to evaluate the filtration and operating characteristics of filters that will be utilized in a cryogenic system. The methods presented herein are intended to supplement standard filter testing specifications to allow evaluation of filter performance characteristics in areas that could be affected by extreme low temperatures. The test methods can be utilized to evaluate filters up to and including 60 gpm (230 lpm) capacity. If higher flow rate filters are to be evaluated in accordance with the test methods presented herein, it will be necessary to increase the system flow capacity and the size of effluent sampling system.

This SAE Aerospace Recommended Practice (ARP) describes two procedures for sampling particles in dust controlled spaces. One procedure covers airborne dust above 5 μm. The other (and newly added procedure) covers particles of 25 μm and larger that “fall out” of the environment onto surfaces. In each case the particles are sized in the longest dimension and counted. Airborne particles are reported as particles per cubic meter (cubic foot) whereas particles collected in fall out samples are reported as particles per 0.1 square meter (square foot). This document includes English units in parentheses as referenced information to the SI units where meaningful. These procedures may also be used for environmental analysis where the quality of the particles by visual or chemical analysis is intended.

It discusses the design choices and engineering trade-offs available to the system designer in the efficient selection and application of Last-Chance filters in contrast to main or primary system filters.

This method describes the procedure for (1) sampling air in contamination controlled spaces for air-borne particulate contamination 5μ or greater in size and for (2) the microscopic determination of the concentration and size range distribution of the particulate material removed from the air sample (Note 1).

This test describes a self-checking procedure for the determination of particulate contaminant five microns or greater in size in hydraulic fluids by the particle count method. A maximum variation of two to one (±33% of the average of two runs) in results should be expected for replicate counts on the same sample, providing that the procedure is followed closely and the precautions presented on pages 10 and 11 of the procedure, regarding manipulation, check samples and self-checking aspects, are observed.

The purpose of this test procedure is to present test methods that can be utilized to evaluate the filtration and operating characteristics of filters that will be utilized in a cryogenic system. The methods presented herein are intended to supplement standard filter testing specifications to allow evaluation of filter performance characteristics in areas that could be affected by extreme low temperatures. The test methods can be utilized to evaluate filters up to and including 60 GPM (330 liters per minute) capacity. If higher flow rate filters are to be evaluated in accordance with the test methods presented herein, it will be necessary to increase the system flow capacity and the size of effluent sampling system.