8. Accumulator Air Charging Valve, Direct Reading Pressure Gage, Brake System__________________________________________________________________________ Pressure Transmitter and HYD BRAKE PRESS Gage (Fig. 4)_____________________________________________
A. The gas line from the lower end of the brake accumulator is connected to a manifold. An Accumulator-Air-Charging Valve installed in the manifold is used to fill the accumulator with gas under pressure. A tube in the left side of the manifold is connected to a Direct-Reading-Pressure Gage. A tube in the right side of the manifold is connected to a Brake Pressure Transmitter which changes pressure to an electrical signal to operate the HYD BRAKE PRESS Gage on the captain's instrument panel. For more information on hydraulic brake indication refer to AMM 32-44-00/001.
B. The Accumulator-Air-Charging Valve, the Direct-Reading-Pressure Gage and the Brake-Pressure-Transmitter are removed and installed using procedures in this section. The Accumulator-Air-Charging-Valve and the Direct-Reading-Pressure Gage are used when you service the accumulator (AMM 12-15-09/301). The HYD BRAKE PRESS Gage is referred to when doing brake system tests and when removing hydraulic pressure from the accumulator.
9. Brake-Metering-Valve-Module Assembly (Fig. 5)____________________________________
A. Two brake-metering-valve-module assemblies (one left and one right) change force on the brake pedals to hydraulic pressure which operates the brakes. The left module supplies pressure to the brakes on the left side of the airplane. The right module supplies pressure to the brakes on the right side of the airplane.
B. The left-brake-metering-valve-module assembly is on the outboard side of the left wing gear wheel well near the aft wall. The right module assembly is on the right side of the airplane directly opposite the left module.
C. Each brake-metering-valve-module assembly contains a control quadrant and a brake-metering-valve assembly. Cables connect the control quadrant to the brake pedals on the flight deck. A lever arm connects the control quadrant to the shaft in the brake-metering-valve assembly.
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WHEEL WELL WING-GEAR-
FWD BRAKE CABLE CONTROL QUADRANT
SEE B SEE A BRAKE CABLE
VALVE ASSEMBLY BRAKE-METERING-
CABLES BRAKE
CONTROL QUADRANT
BRAKE METERING VALVE INSTALLATION (LH SIDE)
A
BRAKE-METERING-VALVE ASSEMBLY
BRAKE METERING VALVE (RH SIDE)
B
Brake Metering Valve Component Location
Figure 5
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MAINTENANCE MANUAL
D. Each brake-metering-valve assembly contains a normal-brake-metering valve, an alternate-brake-metering valve and a wheel despin actuator. Bolts hold these components together. One shaft in the assembly operates the three components. It is attached to a lever arm in the control quadrant.
(1)
Each metering valve contains three ports. One gets fluid from the airplane hydraulic system (the pressure port). One supplies fluid to the brakes (the brake port). One sends fluid to the hydraulic system return lines (the return port).
(a)
A spool in the metering valve opens and closes these ports. The spool is connected by the shaft to the lever arm in the control quadrant. A spring holds the spool in the off position. When it is in the off position, the spool closes the pressure port and opens the brake port to the return port. This permits hydraulic fluid to flow out of the brake lines. As the spool moves under the force of the lever arm it permits fluid to flow from the pressure port to the brake port and stops flow from the brake port to the return port.
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