INTRODUCTION
Two engine-driven pumps normally provide hydraulic pressure for operation of the
landing gear, wheel brakes, flaps, spoilers, and thrust reversers. An electrically driven
auxiliary pump, incorporated for use in the event of system failure, is normally used only
on the ground for operation of the brakes, spoilers, and flaps when both engines are shut
down. It can pressurize all hydraulic subsystems, but should not be used to extend the
landing gear in the event of hydraulic system failure.
GENERAL
A pressurized reservoir ensures a positive sup-
ply of hydraulic fluid to both engine-driven
pumps and to the auxiliary pump. The reser-
voir is pressurized to 10 psi by cabin air drawn
in by an aspirator in the return line, or to 20
psi by regulated engine bleed-air pressure be-
ginning with SNs 24-297 and 25-181.
The engine-driven pumps are either constant-
volume or variable-volume. The pumps are
supplied from lines connected to the side of the
reservoir that reserve approximately .4 gallon
for use by the auxiliary pump that is supplied
by a line connected to the bottom of the reser-
voir. Total reservoir capacity is 1.9 gallons.
CHAPTER 13
HYDRAULIC POWER
SYSTEMS
13-1
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
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