EMERGENCY OPERATION - HYDRAULIC FAILURE
In this case the servo valve ports inside the failed half of the actuator
(pressure loss) are controlled in the normal way allowing hydraulic fluid to be
forced from the dead cylinder by the active half.
This condition is monitored on the CAS window (in addition to pressure
indication) by the microswitch installed on the flow distributor which provides
the caution message 1(2) SERVO.
EMERGENCY OPERATION – VALVE JAMMED
Depending on the main spool valve jammed position, the dual concentric
sleeve valve allows two different way of operations
• if the main spool valve is jammed in the center position (ports in the
inner sleeve closed), the sleeve moves to distribute the fluid to and
from the cylinder in the normal way in response to input commands.
This condition is defined as “actuator active”
• if the spool valve is jammed away from the center position, the sleeve
moves to connect together both control ports, to and from the cylinder,
to the return line. This is a bypass condition and the piston is moved by
the remaining active half of the actuator
In the first condition the pressure line connected to the microswitch is
drained to return only if flight controls are operated so that the caution 1(2)
SERVO is provided to the MFD.
In the second condition the pressure line connected to the microswitch is
always drained to return so that the caution 1(2) SERVO is always provided
to the MFD.
A maintenance check may be performed on the anti-jam device to ensure
that the function is working correctly and that no dormant failures exist in the
components.