Fire Protection

Question 1

How is fire detected in the Engines & APU?

Answer 1

Works on a 2 loop system (A&B) which run in parallel. Heat detectors in the loops detect abnormally high temperatures.
If both loops functioning both need to detect abnormally high temp for FDU to signal fire
If one loop functioning only that needs to detect abnormally high temp

Question 2

Aside from the loops detecting high temperatures how else will a fire signal be activated?

Answer 2

Flames cause both loops to break within 5 seconds of eachother

Question 3

Where do the fire sensing elements of the loops run in each engine?

Answer 3

Engine nacelle
Engine core
Engine fan

Question 4

How many fire bottles are there in each engine and the APU?

Answer 4

Engine - 2
APU - 1

Question 5

What happens when an engine fire push button is pressed? (8 things)

Answer 5

• silences aural warning
• arms fire extinguisher squibs
• closes LP fuel valve
• closes hydraulic shutoff valve
• closes pack flow control valve
• closes engine bleed valve
• cuts off FADEC power supply
• deactivates IDG

Question 6

What happens if the APU fire detection unit detects a fire on the ground?

Answer 6

The APU is automatically shut down and the fire bottle is discharged

Question 7

How if fire detected in the Avionics bay, cargo holds and toilet?

Answer 7

Smoke detectors

Question 8

How many smoke detectors are there in the cargo holds? How many need to detect smoke to send a signal?

Answer 8

Cargo holds - 2 in front hold, 4 in rear hold. Each is connected to one of the fire loops so dual loop principle for setting off a fire warning applies

Question 9

How many smoke detectors are there in the avionics bay and toilet?

Answer 9

Avionics bay - 1 detector will cause fire warning if defects smoke for 5 seconds (no extinguishers)
Toilet- 1 detector in extraction duct of lavatory

Question 10

How many fire bottles are there in the cargo hold?

Answer 10

One bottle with two discharge heads, one for forward, one for aft

Question 11

Is there a fire extinguisher in the toilet?

Answer 11

Only in the lavatory waste bin, which has an automatic fire extinguishing system

Question 12

Is there fire extinguishing available for the avionics bay?

Answer 12

No, only the avionics smoke configuration (set by pressing both BLOWER & EXTRACT to OVRD

Question 13

What happens when the APU fire push button is pressed?

Answer 13

• APU shutdown
• LP fuel valve is closed
• Aural warning is silenced
• APU fuel pump is deactivated
• Squibs are armed
• APU bleed and crossbleed valves close and the APU GEN is deactivated