An increasing number of aircraft manufacturers now recommend use of this type of fluid in aircraft hydraulic systems in preference to mineral hydraulic oils. This move has been prompted by the need to use fluids with better fire resistant properties.
APPROVALS & USE
APPROVED UNDER MIL-PRF-83282D
AeroShell Fluid 31 is also approved for use in the Honeywell (formerly Garrett) cooling turbine (cabin air compressors).
AeroShell Fluid 31 is compatible with AeroShell Fluids 4, 41, 51, 61 and
71 and can be used in systems designed to operate with MIL-PRF-5606,
MIL-PRF-6083, MIL-PRF-87257 and
solvents should not be used for cleaning hydraulic components which use
AeroShell Fluid 31. The residual solvent contaminates the hydraulic
fluid and may lead to corrosion
AeroShell Fluid 31 is a synthetic hydrocarbon oil and should not be used in contact with incompatible seal material.
Mineral hydraulic fluids (MIL-PRF-5606, MIL-PRF-6083) are completely compatible and miscible with synthetic hydrocarbon hydraulic fluids (MIL-PRF-83282, MIL-PRF-87257 and
MIL-PRF-46170) and vice versa.
Mineral hydraulic fluids (MIL-PRF-5606 and MIL-PRF-6083) and synthetic hydrocarbon hydraulic fluids (MIL-PRF-83282, MIL-PRF-87257 and MIL-PRF-46170) are not compatible
with phosphate ester hydraulic fluids and on no account should they be mixed.
CHANGEOVER FROM MIL-H-5606
Since mineral hydraulic fluids are compatible with synthetic hydrocarbon fluids changeover can be easily accomplished.
Two commonly used methods to convert existing MIL-H-5606 based hydraulic systems to MIL-PRF-83282 have been:
(1) draining the aircraft’s hydraulic system or the hydraulic system reservoir of MIL-PRF-5606 and refilling with MIL-PRF-83282, thereafter servicing the aircraft’s hydraulic system with
(2) merely topping off the reservoir with MIL-PRF-83282, as needed. Both methods have been used with great success with no reported problems.