DOC AIRBUS | AMM A320FMISCELLANEOUS - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
A. Drain Assemblies
(1) Small quantities of water collect in the cabin because of condensation. Drains are installed in the fuselage structure to let the water out and to give more protection to the structure from corrosion. The center fuselage drains are located at the lowest point of the cabin, below the cabin floor. They are installed in the rear diaphragm structure and any water is let out through the main gear bay. As the cabin is a pressurized area, the drains are sensitive to cabin pressure and close during normal cabin pressurization.
B. Overpressure Valves
(1) Although the belly fairing is not a pressurized structure, differential pressures can build up between the internal sections. Equal pressures in the sections is maintained by the overpressure valves, located at FR36, left and right, in the structure. The valves open, against spring tension, to release any overpressure build-up in the belly fairing FWD sections. When the valves open, they remain open until the pressure again equalizes between the FWD and AFT sections of the structure.
** ON A/C NOT FOR ALL
Center Fuselage Drains - Component Location3. Description
Fuselage Drains:
The center fuselage drain assemblies have a rubber seal and an upper plate. The rubber seal is sensitive to cabin pressure and will move to close or open a water drain hole. The upper plate limits the movement of the rubber seal when it moves up.
As the cabin pressurizes, the pressure sensitive rubber seal will move down to close the drain hole. When the hole is closed, loss of cabin pressure through the drain hole is prevented. When the cabin pressure decreases the rubber seal will move up to its usual position and open the drain hole. Any water that has collected will drain away through the main gear bay.
Overpressure Valves:
The overpressure valves are sensitive to differential air pressures. The valves open to bleed off excessive pressure when the belly fairing FWD sections are in an overpressure condition. This operation maintains a normal pressure throughout the belly fairing structure at all aircraft altitudes. Each valve has a large piston positioned to close a bleed hole cut in the structure. The piston is held in the normally closed position under spring tension. Any overpressure will act on the piston and force the piston to open against spring tension. As the piston opens, the overpressure bleeds into the belly fairing AFT sections until an equal pressure again exists.
Fuselage Drains:
The center fuselage drain assemblies have a rubber seal and an upper plate. The rubber seal is sensitive to cabin pressure and will move to close or open a water drain hole. The upper plate limits the movement of the rubber seal when it moves up.
As the cabin pressurizes, the pressure sensitive rubber seal will move down to close the drain hole. When the hole is closed, loss of cabin pressure through the drain hole is prevented. When the cabin pressure decreases the rubber seal will move up to its usual position and open the drain hole. Any water that has collected will drain away through the main gear bay.
Overpressure Valves:
The overpressure valves are sensitive to differential air pressures. The valves open to bleed off excessive pressure when the belly fairing FWD sections are in an overpressure condition. This operation maintains a normal pressure throughout the belly fairing structure at all aircraft altitudes. Each valve has a large piston positioned to close a bleed hole cut in the structure. The piston is held in the normally closed position under spring tension. Any overpressure will act on the piston and force the piston to open against spring tension. As the piston opens, the overpressure bleeds into the belly fairing AFT sections until an equal pressure again exists.