(c) Master Brake Cylinders.
When the cylinder is static, an internal spring maintains the extension of
the piston rod and pressure is not present. When the top (toe pressure) of a directional control pedal is pushed,
hydraulic fluid is pressurized. As the upper piston head moves downward, the cap seats against the upper piston
head, stopping the flow of fluid to the reservoir. When the reservoir closes, pressure builds in the upper chamber.
This pressure buildup causes hydraulic fluid to flow through screens in the piston assembly. It also partially
unseats an internal poppet valve. As pressure continues to build in the upper chamber, the piston assembly seats,
trapping fluid in the lower chamber. Increased pressure causes the piston to fully open the poppet, allowing
unused fluid to flow from the upper chamber back to the reservoir. Hydraulic braking pressure is supplied to the
wheel brakes from the lower chamber through an outlet port. When the directional control pedals are released, a
spring inside the upper chamber extends the cylinder to its original length, relieving fluid pressure and
depressurizing the system.
(d) Parking Brake System.
The parking brake system (fig. 317) sets the wheel brakes for stability.
During normal braking operation, with the brake pedal actuated, the lever of the parking brake valve is held in the
off position by a spring assembly. The lever is attached to a camshaft which holds the two outer valves open. Fluid
pressure is applied to the MLG wheel brakes by applying pressure to the toe portion of the pilot or CPG directional
control pedals. The master brake cylinders force fluid through the transfer valves, parking brake valve, and
connecting brake lines to the wheel brakes. With the parking lever in the unlock position, the inner valves are
seated (closed) and the compensators are inoperative.
ASSY (4 EA)
BALL & SEAT
PARKING BRAKE VALVE
Parking Brake System Operational Schematic
MULTIPLEX READ CODES