A-1 CHARGING CUTOFF PILOT VALVE (cont)
28. Test the A-1 charging cutoff valve in accordance with Test Specification T-2617.
The A-1 charging cutoff pilot
valve functions as follows:
During normal brake operation, the A-1 charging cutoff pilot valve will be in its normal position as follows:
(1) Main reservoir air will be present in chamber A, beneath the cutoff piston head to hold it in its upper position.
Chamber B beneath the cutoff piston spool valve will be connected to exhaust via port 53 and the cutoff pilot
valve exhaust in the 26-C brake valve on leading units.
(2) Chamber C, above the cutoff piston and port 9, is connected to exhaust via the actuating piston spool valve
and automatic sanding timing choke.
(3) Brake pipe flows through port 1 to chamber D surrounding the back side of the actuating piston, through the
choke in the piston to chamber E at the outer face of the piston, and though port 11 to the 90-cubic-inch
(1475 cc) volume reservoir, charging the volume reservoir and both sides of the actuating piston to brake
(4) Port 35 and the chamber beneath the dynamic cutout switch are exhausted through the cutoff piston spool