Engine Fire Protection
Engine fire protection consists of these systems:
- Engine overheat and fire detection powered by the battery bus.
- Engine fire extinguishing powered by the hot battery bus.
Engine Overheat and Fire Detection
Each engine contains two overheat/fire detector loops. Each loop provides both fire and
overheat detection. As the temperature of a detector increases to a predetermined limit, the
detector senses an overheat condition. At higher temperatures, the detector senses a fire
condition. Normally, both detector loops must sense a fire or overheat condition to cause
an engine overheat or fire alert.
The ENG OVERHEAT light or engine fire warning switch remains illuminated until the
temperature drops below the onset temperature. An OVHT DET switch for each engine,
labeled A, B, and NORMAL, permits selection of either loop A or B, or both A and B, as the
active detecting loops. The system contains a fault monitoring circuit. If one loop fails with
the OVHT DET switch in NORMAL, that loop is automatically deselected and the remaining
loop functions as a single loop detector.
There is no flight deck indication of single loop failure. If both loops fail on an engine, the
FAULT light illuminates and the system is inoperative. If the OVHT DET switch is positioned
to A or B, the system operates as a single loop system. The non–selected loop is not
monitored. If the selected loop fails, the FAULT light illuminates and the system is
inoperative.
