BOMBARDIER BD-100-1A10, Operating Manual

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FIRE PROTECTION
Volume 2 Flight Crew Operating Manual Sep 13/2004
09-01-04
CSP 100-6
REV 1
ENGINE FIRE DETECTION
DESCRIPTION
The engine fire detection system functions by detecting an overheat condition on the exterior of the engine.
If a fire is detected in the engine, the affected L or R ENG FIRE switch illuminates along with the master warning light,
the master warning chimes, a L or R ENGINE FIRE (W) CAS message, a FIRE EI red in the N
1
indicator, and the aural
LEFT or RIGHT ENGINE FIRE.
The engine fire extinguishing system includes two bottles. If required, both bottles can be discharged into either engine.
COMPONENTS AND OPERATION
DETECTION LOOPS
Each engine is installed with dual fire detection loops. The loops provide fire detection around the core engine area, engine
accessory area, forward nacelle and pylon areas. The loops are connected to the fire detection and extinguishing control
unit (FIREX-CU). The loops are constructed of an outer metal sheathing and two internal wires that are separated by an
insulating material (thermistor). One of the wires carries electrical current; the other is grounded to the outer sheathing at
the control unit. The resistance of the thermistor decreases with an increase in temperature.
When the electrical resistance decreases to a trip point, electrical current from the live internal wire conducts to the second
internal wire and a fire indication is generated.
This loop system minimizes the possibility of false fire warnings. Both loops must sense the fire or overheat condition un-
der similar parameters before flight deck fire indications are generated.
FIRE DETECTION AND EXTINGUISHING CONTROL UNIT
The fire detection and extinguishing control unit is the aircraft fire protection system electronic control unit that monitors
the electrical resistance of the loops. The control unit is located in the aft equipment bay. When both loops experience the
same decrease in resistance within a preset time, the control unit sends a fire signal to the EICAS. Each individual control
circuit and its related sensing loop is monitored. If one loop malfunctions, the second loop can still detect a fire.
FIRE EXTINGUISHER BOTTLES
Two fire extinguisher bottles are installed in the aft equipment bay. Each are equipped with a pressure switch, pressure
gauge, two discharge heads on the number 1 bottle, and three discharge heads on the number 2 bottle. Each squib has two
firing bridgewires fed by separate electrical circuits and are installed on each fire bottle. The bottles are filled with Halon
1301.
If required, both bottles can be discharged into one engine. The selection of the L or R ENG FIRE switch determines which
squib is fired. Only bottle No. 2 can be discharged into the APU compartment.
Both fire extinguishers are installed outside the aircraft’s pressure bulkhead in the aft equipment bay. For the left and right
engines, a check tee is placed at the intersection between the plumbing from the two bottles and the common plumbing
going to the fire zone. The check tee prevents extinguishing agent from the second discharged bottle from back filling into
the bottle that was discharged first.