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|  MIL-H-8891A
Power pumps - The hydraulic system pump(s) shall be
3.4.1
compatible with the installed vehicle system and shall not cause abnormal
or undesirable effects on the installed system in the vehicle. In each
system, the primary pump applications which normally require continuous
operation shall be provided with at least two qualified pump designs from
separate manufacturing sources on production aircraft. All pumps qualified
for a given application shall be physically and functionally interchangeable
and shall be compatible with the system and with each other to allow mixed
use in multiple pump systems.
Multiple pumps, engine-driven - Multiple engine vehicle
3.4.1.1
hydraulic systems using engine-driven pumps shall have pumps driven by at
least two engines. A sufficient number of engine-driven pumps, augmented
where necessary by pumps driven from other sources of power (e.g., electric
motors, auxiliary power units, ram-air turbine, or pneumatic drives), shall
be provided to assure operation of control surface boost or power systems
with any minimum combination of engines which will maintain flight and to
assure operation of power brake systems and any other services needed during
taxiing with any minimum combination of engines which may be used for taxiing.
Pumps, variable-delivery - Variable-delivery pumps shall
3.4.1.2
be in accordance with MIL-P-19692. For pumps the pressure differential between
the pump-case cooling port and the reservoir shall be such as to permit the
pump to maintain adequate cooling flow in any pump flow condition.
3.4.1.3
*
Electric-motor-driven pumps - Electric-motor-driven
hydraulic pumps in accordance with MIL-P-5954 or MIL-P-5994 may be used, as
necessary, for either normal, emergency, or auxiliary operation of hydraulic
systems.
Emergency power
ps - Hydraulic pumps required to
3.4.1.4
provide emergency power for direct application to flight controls or other
essential hydraulic flight requirements shall not be used for any other
function.
*
Pump pulsation - For all power-generating components
3.4.1.5
(engine pumps, power packages, transfer units, etc.), pump pulsations shall
be controlled to a level which does not adversely affect the vehicle system
tubing, components, and supports installation. The contractor shall deter-
mine by test the effect of pump pulsations (pump ripple) on the hydraulic
system. Initial tests shall be conducted on the functional mockup and
simulator, with suitable recording equipment, and shall cover the complete
speed range from start up to the maximum speed, pressures and flows that
the pump will be subjected to when installed in the vehicle, Adverse effects
including induced resonant vibrations shall be eliminated. Results of the
functional mockup/simulator tests for pump ripple effects shall be documented
forwarded to the procuring activity, and shall be verified on the first
vehicle, and any additional major corrections required shall be made prior to
the first flight.
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