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This SAE Aerospace Information Report (AIR) provides technical information to assist the development of specific cleaning methods for those filter elements which are designated as "cleanable" and cannot be cleaned by simple and obvious procedures.

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 Information Report (AIR) provides technical information to assist the development of specific cleaning methods for filter elements. Consideration is limited to filter elements which are designated as "cleanable" (not "disposable"), but which cannot be cleaned by simple and obvious procedures. Cleaning methods developed according to this report should be evaluated by the methods of ARP725. Satisfactory cleaning methods can be developed for most "cleanable" filter elements. Technical or economic feasibility of the cleaning method may be limited, however, by incompatibility of filter-element construction materials, by mechanical weakness or lack of corrosion resistance to withstand repeated or continued cleaning, or by the presence of unusually tenacious contamination. These factors must be considered when selecting approaches to the development of specific methods.

This SAE Aerospace Information Report (AIR) describes a mathematical model that can be used to analyze particle count data. Particle counts that fit the model can be graphically displayed, converted from one counting size-frequency range to another, and extrapolated to estimate counts beyond the measured range. Derivation, applications, and calculations are described.

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 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.

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 Aerospace Information Report (AIR) describes a mathematical model that can be used to analyze particle count data. Particle counts that fit the model can be graphically displayed, converted from one counting size-frequency range to another, and extrapolated to estimate counts beyond the measured range. Derivation, applications and calculations are described.

This report describes a mathematical model which can be used to analyze particle count data. Particle counts which fit the model can be graphically displayed. converted from one counting size-frequency range to another, and extrapolated to estimate counts beyond the measured range. Derivation, applications and calculations are described.

These recommendations are written to cover the subject of obtaining filter patch test samples from aerospace hydraulic equipment of the categories shown below. The same procedure shall apply regardless of the unit category.

These recommendations are written to cover the subject of obtaining filter patch test samples from aerospace hydraulic units of the categories shown below. The same procedure shall apply regardless of the unit drive category.

This Aerospace Information Report provides technical information to assist the development of specific cleaning methods for filter elements. Consideration is limited to filter elements which are designated as "cleanable" (not "disposable"), but which cannot be cleaned by simple and obvious procedures. Cleaning methods developed according to this report should be evaluated by the methods of ARP 725 and ARP 849. Satisfactory cleaning methods can be developed for most "cleanable" filter elements. Technical or economic feasibility of the cleaning method may be limited, however, by incompatibility of filter-element construction materials, by mechanical weakness or lack of corrosion resistance to withstand repeated or continued cleaning, or by the presence of unusually tenacious contamination. These factors must be considered when selecting approaches to the development of specific methods.

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.

This ARP describes procedure for determining the counting and sizing accuracy for an automatic liquid-borne particle counter (APC). This procedure is used in conjunction with a suspension of precisely sized spherical particles.

This Aerospace Recommended Practice covers the calibration and verification of automatic liquid-borne particle counter for the determination of the concentration by number and size distribution of particles in aerospace liquids. This method is intended for the standardization of automatic liquid-borne particle counting instrumentation.

This test describes a self-checking procedure for the determination of particulate contaminant five microns or greater in size in air 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 regarding check samples and self-checking aspects are observed.