I A P 2 0 2 3 . 0 0 1 - A F M / I R I S T E X A N I I P A G E | 46
FOR SIMULATION USE ONLY – NOT A TRAINING AID
HYDRAULIC SYSTEM
The hydraulic system consists of one engine driven pump with approximately a 5-
quart capacity. The system incorporates a pressure relief valve (3250 to 3500 psi) in
the main and emergency systems to prevent damage from high system pressure.
The hydraulic system service bay, located in the lower aft fuselage behind the right
wing trailing edge, contains:
A manual pressure release handle to release the pressurized fluid from the
emergency accumulator back to the reservoir.
A fluid quantity indicator which shows the level of hydraulic fluid in the
power package reservoir.
A ground hydraulic power, sampling, and servicing connection.
NORMAL OPERATION
The hydraulic pump pressurizes the normal system and emergency accumulator to
3000±120 psi through a hydraulic fuse and one-way check valve.
Once pressure exceeds 1800 psi, the system can power the landing gear, main gear
doors, flaps, speed brake, and nose wheel steering. If the hydraulic pressure
indicator drops below 1800 psi, the hydraulic pressure display changes from white
to amber.
An amber HYD FL LO caution illuminates on the EICAS display to indicate that the
reservoir level has dropped below approximately 1 quart.
Hydraulic fluid level is checked in the hydraulic system service bay by comparing
the position of the green indicating rod to marked indicator windows. The window
indicates FULL AC when the fluid level is full, and the accumulator is charged.
If the fluid level is not FULL AC or FULL AD, then depressurize the emergency
accumulator by pulling the manual pressure release handle. As the accumulator
discharges, the fluid level in the reservoir should increase.
The system must be serviced if the accumulator is fully discharged and the fluid
level does not indicate FULL AD. Power for the hydraulic system is provided
through a circuit breaker, placarded HYD SYS, located on the battery bus circuit
breaker panel in the front cockpit.
With this circuit breaker open, the pressure indication and HYD FL LO sensor is not
available, but EHYD PX LO sensor is available.
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