HYDRAULICS
Description
Aircraft Operations Manual
10.1
PAGE
1
Aprr 01/15
1.
GENERAL
Hydraulic power is used to operate the following
aircraft systems:
−
Flaps.
−
Landing gear.
−
Brakes.
−
Nose wheel steering.
−
Propeller brake.
An electrically driven pump normally supplies hy-
draulic pressure to four accumulators. For emer-
gency and certain maintenance uses, a hand pump
is installed.
The electrical pump is controlled by a single switch
in the cockpit.
The four hydraulic accumulators provide pressure
as follows:
−
One main accumulator supplying flaps, landing
gear, nose wheel steering and propeller brake.
−
One emergency accumulator supplying landing
gear emergency uplock release.
−
Two accumulators for the brake system, one for
the outboard brakes and one for the inboard
brakes.
All hydraulic system components are located in the
nose area on each side of nose wheel well (left and
right hydraulic compartment).
Hydraulic fluid used in the system is mineral based
MIL
−
H
−
5606. The fluid is red for identification and
easy detection of leaks.
2.
MAIN COMPONENTS AND SUBSYSTEMS
(Fig. 1)
2.1
Hydraulic reservoirs
Main reservoir
The main reservoir has a capacity of 310 cubic
inches (approx. 5 liters). The reservoir is pressur-
ized from the emergency accumulator circuit to pro-
vide a positive pressure supply to the hydraulic
pump. In case of loss of pressurization, a spring will
ensure a positive fluid supply.
Hand pump reservoir
The hand pump reservoir supplies hydraulic fluid to
the hand pump exclusively. It has a capacity of 150
cubic inches (2.5 liters) and is filled through a gravi-
ty fill port. Overflow from the main reservoir relief
valve and bleed valve is also directed into this res-
ervoir.
2.2
Hydraulic pumps
Electrical pump
The electrically powered pump provides hydraulic
pressure for all normal operation.
The pump is automatically shut off to prevent op-
eration when there is no demand. The electric mo-
tor for the pump is controlled by a pressure switch
in the main accumulator hydraulic circuit and by
landing gear operation.
The pump will operate automatically when:
−
The main accumulator hydraulic pressure drops
below 2100 psi and until the pressure reaches
2900 psi.
−
Landing gear is selected DOWN and until left
main gear is locked down.
−
Landing gear is selected UP and until both main
gears are locked up.
−
R PROP BRK switch is selected ON.
If required, automatic pump control may be overrid-
den by using the override (OVRD) position of the
HYD PUMP switch enabling the pump to run contin-
uously. In OVRD the pump delivers hydraulic fluid
with a pressure of 3000 psi.
Hand Pump
Should the electric pump fail Main, Outboard and
Inboard brake accumulator may be pressurized
from a hand pump to the right of the center pedes-
tal. The hand pump is operated by a detachable
handle stowed on the right, rear cockpit wall.