Drain mast ice protection

Each CU regulates the heating temperature of the associated drain mast tube between 6°C (43°F) and 10°C (50°F). In case of a failure of a drain mast heater, the fault will be displayed on the Programming and Test Panel or the Flight Attendant Panel (FAP) of the Cabin Intercommunication Data System (CIDS). The aircraft may be dispatched per Minimum Equipment List with the drain mast heater inoperative.

The water supply to the LAVatory(ies) (LAV(s)) and galley which use the failed drain mast must be shut off. As a result, the LAV(s). will not be usable and must be secured closed and locked.

SERVICE PANEL LOCATION