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 | 47
FOR SIMULATION USE ONLY – NOT A TRAINING AID
EMERGENCY OPERATION
Emergency hydraulic pressure is available after the normal system has
pressurized the emergency accumulator. Pulling the emergency gear extension
handle (see Figure 1-2) in the front cockpit activates the emergency system by
isolating the main hydraulic system at the power pack slide assembly and releasing
the emergency accumulator pressure through independent emergency lines to
extend the landing gear and flaps.
An amber EHYD PX LO caution on the EICAS is illuminated when the emergency
accumulator pressure drops below 2400 ±150 psi and is the only indication of the
emergency accumulator’s status.
A check valve prevents the emergency system from bleeding back into the main
system if the main system fails. A hydraulic fuse is used to prevent a leak in the
emergency system from depleting the main hydraulic system.
The fluid flow to the emergency accumulator is restricted to a rate below .25 GPM.
In the event of an emergency hydraulic system leak that exceeds .25 GPM, the fuse
limits fluid loss to a maximum volume of 20-30 cubic inches (0.5 quarts).
The EHYD PX LO caution illuminates, and the landing gear and flaps may be lowered
using the main system. If the leak rate is below .25 gallons per minute (GPM), the
system depletes the main reservoir until the HYD FL LO caution illuminates, at
which time there will still be sufficient fluid in the main reservoir to lower the
landing gear and flaps using the main system.
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