I
MIL-H-8891A
Reservoir venting - If a vent is provided in the reser-
3.4.2.5
voir, it shall be so arranged that loss of fluid will not occur through the
vent-during flight maneuvers or ground operations of the vehicle. A filter
in accordance with AN6240 shall be incorporated into the vent line if the
temperature requirement is suitable. If a filler cap is used, the act of
removing the filler cap shall automatically vent the reservoir in such a
manner that the energy contained in the pressurizing air is not dissipated
by imparting kinetic energy to either the filler cap or the fluid contained
in the reservoir or elsewhere in the system.
Gas-pressurized reservoirs - The gas pressure shall be
3.4.2.6
controlled by an externally nonadjustable pressure-regulating device to con-
trol the gas pressure in the reservoir. A relief valve shall also be con-
nected to the gas space to protect the reservoir and pump from excessive
pressure. If the pressure regulator and relief valve are combined into one
housing, a single failure in that unit shall not permit overpressurization
of the reservoir. Devices that introduce air into the hydraulic fluid shall
not be used. When the gas is separate from the fluid by a piston or other
device, operation of the system shall not introduce gas into the hydraulic
fluid . Provision shall be made to remove entrained gas which may have entered
the system during servicing or operation.
Reservoir air pressurization moisture removal equipment-
3.4.2.7
When engine bleed air is used for reservoir pressurization a suitable mois-
ture removal unit shall be so located as to protect the pressure regulation
lines and equipment. An adequate filter shall be provided.
Reservoir fluid level Indication - Reservoir fluid level
3.4.2.8
indication shall be provided in the cockpit. Indicator fluid level markings
shall correspond with the direct-reading fluid level indicator markings pro-
vided on the reservoir and shall be lighted in accordance with applicable
.
cockpit lighting requirements. A suitable warning light shall also be pro-
vided to advise the pilot of a low fluid level condition. The cockpit fluid
level indicator shall not eliminate the requirement for the direct-reading
fluid level indicator on the reservoir itself, as this is required for reser-
voir servicing with power OFF.
Reservoir bootstrap pressurization - Reservoir pressurize- ,
*
3.4.2.9
tion shall be maintained in the event normal system pressure (reservoir bootstrap
pressure) is lost due to an air-lock. Maintaining reservoir pressurization will
minimize pump pressure recovery time.
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