TM 55-1520-240-23-6
7-135
UTILITY HYDRAULIC SYSTEM
(Continued)
7-135
Wheel Brake System Theory of Operation
Hydraulic fluid at a pressure of 3,000 psi from the utility
system pressure control module is reduced to 1,390
psi in a pressure reducer at sta. 502 left side. The
fluid continues through a check valve to a 25 cubic
inch accumulator. The check valve prevents the brake
system from being depleted in case of utility system
failure.
NO BREAK - WORK HARDER
Fluid from the accumulator enters the four brake
cylinders. Two transfer valves combine the pressure
output from the cylinders into one line for the left brakes
and one line from the right brakes. The two lines enter
a parking brake valve. When the brake pedals are
pressed, fluid under pressure flows through the valves
into each brake assembly. Within each assembly, the
pressurized fluid presses three floating pads against a
disk that rotates with the wheel. The floating pads press
the rotating disk against three fixed pads on the opposite
side of the disk. When the pedals are pressed and
the cockpit parking brake handle is pulled, pressurized
fluid is trapped between the parking brake valve and
the brakes. The valve keeps the brakes engaged by
holding pressure against the brake disks. Pulling the
brake handle also activates a microswitch on the parking
brake valve that lights a PARK BRAKE ON light on the
master caution panel.
NO BREAK - WORK HARDER
When pressure against the brakes is released, fluid
returns through the brake cylinders and past a check
valve into the utility system return control module.
END OF TASK
7-621
