the engine nacelle rises to a specified thresh-
old as follows:
• Accessory area element – 410° F.
• Firewall element – 410° F.
• Hot Section element – 890° F.
When the sensing element is heated to the
above temperatures, the electrical resistance
in the sensor is reduced, allowing sufficient
current to flow between the conductor and the
tube, activating the fire detection control unit.
If a short occurs anywhere in the element,
while inflight it will be detected and a white
“L or R ENG FIRE FAIL” message will be
displayed on the CAS.
An amber “LR ENG FIRE FAIL” CAS mes-
sage will appear if the engine fire detect sys-
tem has detected a fault while on the ground
that may not allow the detection system to in-
dicate a fire.
Electrical power for each engine detection
system is 28 VDC, supplied through the left
and right FIRE DET circuit breakers located
in the left and right engine circuit breaker
groups. The engine fire detection systems are
powered from the respective left and right es-
sential busses. The fire extinguishers and shut-
off valves are powered by the left and right hot
busses, and are functional without external or
airplane electrical power turned on.
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
8-2
FOR TRAINING PURPOSES ONLY
FlightSafety
international
410
°
F SENSING
ELEMENT
(PYLON FIREWALL)
L FIRE
DETECT
L ESS
BUS
410
°
F SENSING ELEMENT
AND SUPPORT FRAME
ELEMENT
SUPPORT
FRAME
890
°
F SENSING
ELEMENT
COMBUSTION
SECTION
FIRE
DETECTION
CONTROL
UNIT
FIRE
PUSH
CLOSED
L R ENG FIRE FAIL
L R ENG FIRE FAIL
ENGINE FIRE SENSING
ELEMENT IS SHORTED.
ON GROUND
INFLIGHT
Figure 8-1. Engine Fire Detection System