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S8C22 - HYDRAULIC FLUID SYSTEMS/EQUIPMENT
Table of Contents
1. Hydraulic fluid systems and equipment are extremely sensitive to the ingress of minute foreign particles and water. These can cause rapid wear, system degradation, serious aeronautical product malfunction and ultimately system failure. The correct specification and quantity of fluid, together with appropriate maintenance and servicing procedures will ensure maximum system performance and serviceability.
2. This chapter prescribes the AMO procedures to be followed when managing the maintenance and operation of hydraulic fluid systems and equipment.
3. When operating, servicing or maintaining aircraft or Ground Support Equipment (GSE) hydraulic fluid systems the following procedures are to be followed:
4. The replenishment of aircraft hydraulic fluid systems is to be performed by dispensing equipment with 3‑micron (absolute) filtration. A juniper rig, fitted with 5–micron filters, may be used for servicing of aircraft if a 3‑micron filtering unit is unavailable. Dispensing equipment containers are to be marked with the type of hydraulic fluid contained within, and are only to be used for that particular fluid. All dispensing equipment is to be serviced on a periodic basis, including filter servicing in accordance with the relevant technical publication.
5. If approved by the SPO, aircraft hydraulic fluid systems may be replenished directly from a freshly opened hermetically sealed can, provided that all other requirements detailed in this chapter are satisfied.
6. Hydraulic fluid reservoirs are to be replenished to the maximum permissible quantity as specified in the relevant aircraft publication.
7. Only the fluid specified in the relevant aircraft publication (or an approved alternative) is to be used in replenishing an aircraft hydraulic fluid system. If required record the quantity of hydraulic fluid added to the aircraft in the aircraft’s maintenance documentation.
HYDRAULIC FLUID SAMPLING PROCEDURES
8. Aircraft hydraulic fluid systems are to be sampled and analysed on the following occasions:
9. Samples from the aircrafts hydraulic fluid system are to be taken as soon as possible after aircraft shutdown, prior to system replenishment. The period between shut down and sampling is not to exceed 20 minutes unless otherwise stated in the relevant maintenance publication. If this cannot be achieved, the system is to be cycled in accordance with relevant maintenance publications, to ensure the hydraulic fluid has cycled through the system prior to sampling.
Ground Support Equipment
10. GSE (hydraulic test equipment) used in the servicing, testing or replenishment of aircraft or aeronautical product hydraulic fluid systems, are to be cycled and tested before connection to such systems and are to also have the following:
11. If any discolouration has occurred, water or sediment is evident, or excessive contamination is identified by the CMS, the GSE is to be drained, flushed, refilled and cycled in accordance with paragraph 12 and the fluid retested.
12. Cycling. Cycling is carried out to bring the hydraulic fluid to temperature and also allow CMS, where fitted, to settle and provide accurate readings. Prior to taking samples or carrying out tests, GSE is to be cycled in accordance with AAP 7605.014‑2M -Contamination Control Hydraulic Test Rigs and Benches or other applicable technical publications; however, in the absence of technical instructions, GSE is to be cycled as follows:
13. To minimise the introduction of contaminants into the sample, sampling points, equipment and bottles are to be cleaned immediately before taking a sample by:
14. When the sampling bottle, point and equipment are dry, samples are to be taken using the following steps:
15. Each sample is to be labelled with:
Aircraft and GSE Hydraulic Fluid System Analysis
16. The routine method of analysis is the colour patch method, keeping a full record of each analysis carried out. If a more comprehensive analysis is required, the responsible SPO will issue further instructions.
17. Where a sample fails the colour patch test, the relevant system is to have the filters changed or cleaned, the system cycled in accordance with paragraphs 8 and 9, as applicable, and the test repeated. If this sample fails a second time, the system is to be drained, flushed, refilled and cycled in accordance with paragraphs 9 and12, as applicable. The sample is to be forwarded to a laboratory as designated by the responsible SPO. Dependent on the results of this test, the responsible SPO will advise further action to be taken.
Hydraulic fluid samples are to be adequately packaged to ensure no leakage occurs during transit. This includes the taping of sample bottle lids and the packaging of samples in a container filled with absorbent material.
18. Colour patch testing is performed utilising a Contamination Analysis Kit, Part No XX65 047 00, which enables effective monitoring of the quality aircraft hydraulic fluid systems and associated GSE. The test kit is used for rapid monitoring of the degree of particulate contamination by observing the degree of discolouration of a disc filter through which a standard volume of test liquid has been drawn by vacuum filtration. The colouration of the filter is then compared to recognised standard levels of contamination, in accordance with the instructions supplied with the kit.
19. The date and the result of the aircraft hydraulic fluid sample inspections are to be entered in the applicable recording and certification system. Sampling of GSE must be recorded in the respective GSE servicing record.
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