pushing the crank assembly aft and rotating the
shaft. The rotation of the shaft extends the
operating gear linkage and raises the panel
assemblies. Fluid from port B of the piston is
directed through the 4-way valve assembly and
back to the gravity tank.
To lower the JBD (fig. 12-11), solenoid A of
the 4-way control valve assembly is energized. The
spools of the 4-way valve assembly shift, allow
medium-pressure hydraulic fluid to flow into port
B of the hydraulic cylinder. The cylinders retract,
pulling the crank assembly forward and rotating
the shaft. The rotation of the shaft retracts the
operating gear linkage and lowers the panel
assemblies. Fluid from port A of the piston is
directed through the 4-way valve assembly and
back to the gravity tank.
To lower the JBD in the event of hydraulic
control failure, each JBD panel is equipped with
a manual bypass valve, which allows bypassing
the 4-way control valve. This allows venting the
hydraulic pressure from the “raise” side of the
cylinder back to the gravity tank.
The three lines to port A of the hydraulic
cylinders have orifice assemblies in them. These
orifice assemblies control the flow of hydraulic
fluid in both the raise and lower operations.
12-13
