Discharge Valves and Ground Automatic Relief Valves

Discharge Valves and Ground Automatic Relief Valves

At intervals specified in the Aircraft Maintenance Schedule, the pressure controlling function should be tested. These tests are normally done in situ and in conjunction with the associated pressure controller. The security and functioning of ditching system controls, where fitted, should also be carried out.

Valve faces and seats should be inspected for damage and deposits of dust and nicotine tar which should be removed in the manner specified in the relevant Aircraft Maintenance Manuals. The cleaning fluids used should be of the type recommended by the manufacturers, and on completion of a cleaning operation all traces of fluid should be removed and all surfaces cleaned using a dry, soft, lint-free cloth. High pressure air blasts should not be used to dry the seating surfaces of diaphragm ­controlled discharge valves as damage may be caused to the diaphragms. Bonding leads and their attachment points should be inspected for security of attachment and checked for electrical continuity.

At specified periods, discharge valves should be removed, inspected, and leak tested to ensure that the leak rate is within specified permissible limits. After reinstatement or replacement of a discharge valve a full functional check should be carried out.

NOTE: On some aircraft types, shims are installed to aerodynamically align the discharge valve, with the fuselage. When removing the valve from the aircraft these shims should be retained in order to maintain that alignment when replacing the valve.