Both engines and the APU each have two identical loops, A
& B and a computer- FDU (Fire Detection Unit). A fire warning is given when
both loops reach the proper overheat condition. If one loop fails the other
loop is able to generate the warning by itself. A fire warning is given if both
loops fail within 5 seconds of each other. There is a red disc on the aft
fuselage to show thermal discharge for the APU fire bottle. The engines each
have two extinguishers, the APU one. Engines have sensing elements in three
sections; pylon nacelle, engine core and fan section. APU has sensing element
in APU compartment.
APU fire on ground will auto shutdown, sound nose wheel well
horn and APU FIRE light will illuminate on external interphone panel. APU fire
in-flight must be manually shutdown (will not auto shutdown) and extinguished. Note:
APU will auto shutdown in air for other than fire (go figure).
The forward cargo compartment has two smoke detectors and the aft has four (319,320). The 321 has four forward detectors and six detectors in the aft cargo. Agreement of two smoke detectors on a loop will give warning. If one smoke detector fails the system remains operational on the remaining detector. There is one extinguisher bottle for fore and aft compartments with one nozzle forward and two nozzles aft. If cargo SMOKE is warning is given an isolation valve will close and the extraction fan will stop. Cargo smoke gives: CRC, Master Warn light and Cargo SMOKE light.
ENG 1 Test – press and hold
Ø ENG FIRE
pb illuminated (red)
Ø SQUIB and
DISCH lights illuminated (2)
Ø MASTER
WARN illuminated (2) (red)
Ø CRC aural
chime
Ø ENG 1 FIRE
warning on E/WD (red)
Ø ENGINE
page on SD
Ø FIRE light
ENG 1 (on ENG panel) illuminated (red)
Repeat for ENG 2
APU fire test: (BAT only 2 items – 1 red, AC 6 items – 3
red) (PH3.3, 8.2.2)
Ø APU FIRE
pb illuminated (red) *
Ø SQUIB and
DISCH light illuminated *
Ø MASTER
WARN lights illuminated (2) (red)
Ø CRC aural
chime
Ø APU FIRE
warning on E/WD (red)
Ø APU page
on SD
* BAT only (when doing Safety and
Power On checklist on Battery only, no External power)
ENG FIRE pb pressed performs: (work down panel with
2,1,2,1,2 sequence – two on FIRE, one on HYD, two on FUEL, one on ELEC, two on
AIR COND)
FIRE - Silences
CRC, Arms squibs (2)
HYD – Closes
hydraulic fire valve (1)
FUEL - Closes
low pressure fuel & engine IDG fuel return valves (2)
ELEC - Trips
ENG GEN (1)
AIR COND- Closes
engine bleed & pack flow valves (2)
APU FIRE pb pressed performs: (work down panel with 3, 0,
2,1,2 sequence)-
FIRE - Silences
CRC, Shuts down APU, Arms squib (3)
HYD - (0)
FUEL - Closes
low pressure fuel valve & APU fuel pump off (2)
ELEC - Trips
APU GEN (1)
AIR COND- Closes APU
bleed & Crossbleed valves (2)
Cargo Smoke Detector test - press & release button for
test. You should get (PH 3.4.1):
Ø DISCH
amber lights illuminate.
Ø SMOKE red
lights illuminate
Ø MASTER
WARN light illuminate
Ø CRC
Ø CARGO
SMOKE on E/WD
This test will run twice after you select it once to test
both channels. Note: DISCH amber lights only on first test.
If the CARGO SMOKE bottle is fired the indications you can
expect are:
Red SMOKE light remains on (smoke & bottle discharge are
trapped)
Both amber DISCH lights will come on and remain on (only one bottle)