The aircraft vegetable-base fluid is colored with a blue dye
for identification and is designated MIL-H-7644.
automotive hydraulic systems is amber in color.
designation of this fluid is MIL-F-2111.
Remember: Neither of these fluids are acceptable for use in
aircraft hydraulic systems, and are NOT to be used in hydraulic jacks
or other aircraft ground-handling equipment.
Mineral-Base Hydraulic Fluids.
Three categories of mineral base
hydraulic fluids are used in Army aviation today: operational,
preservative, and cleaning.
During extreme cold weather the operational
fluid now used in aircraft hydraulic systems and components is MIL-H-
This fluid is colored with a red dye for identification and
has a very distinctive odor. MIL-H-83282 is to be used in components
and systems as prescribed in TB 55-1500-334-25.
Preservative fluid contains a special
Its primary purpose is to fill
hydraulic components as a protection against corrosion during
shipment or storage.
Designated as MIL-H-6083A, preservatite fluid
is very similar to operational fluid in viscosity, odor, and color.
Operational fluid, MIL-H-5606, and preservative fluid, MIL-H-6083A,
are compatible but not interchangeable. Therefore, when preparing to
install components preserved with 6083A, the preservative fluid must
be drained to the drip point before installation, and the components
refilled with operational fluid. The preservative fluid, 6083A, need
not be flushed out with 5606.
When using MIL-H-83282, the
preservative must be flushed as prescribed in TB 55-1500-334-25.
Cleaning Fluid. TM 55-1500-204-23-2 contains a list of authorized
cleaning agents and details their use in hydraulic systems and
Because of constant improvement of cleaning agents,
changes to the basic technical manual are printed and distributed as
For that reason, always refer to the current technical
manual and its latest changes, for the authorized cleaning agent to
be used on types of hydraulic systems and components.
Table of Fluid Uses.
The following table is a brief summary of
the permissible uses of mineral-base hydraulic fluids.