8 - fire and overheat protection

Question 1

What are the four areas with fire and overheat protection?

Answer 1

Engine
Jet pipes and pylons
APU
Main landing gear

Question 2

What two areas have smoke detection systems?

Answer 2

Cargo bay

Lavatory

Question 3

What areas of the engine have fire and overheat protection?

Answer 3

Fire and overheat protection are provided in the jet pipe, nacelle, and pylon areas. These are divided into two zones, the engine area which is the core of the engine and second is the jet area which is the jet pipe and pylon

Question 4

This fire extinguishing provided in both the engine and jet zones of the engine?

Answer 4

Fire extinguishing is provided in the engine zone only. Detection is provided in the Jet and pylon zone.

Question 5

What ducting is contained in the jet zone?

Answer 5

10th stage and 14th stage bleed air ducting are contained in this zone.

Question 6

What in the engine actually detects the fire or overheat condition?

Answer 6

There are two detection loops labeled a and B, Which are connected to a control unit. As there is an increase in temperature the electrical resistance of the insulator decreases with an increase in temperature to a trip point at which there’ll be a fire or overheat indication generated.

Question 7

How are the detection loops arranged in the engine zone?

Answer 7

The detection loops are located in the aft engine core and the side of the cowl panel that is near the fuselage

Question 8

How are the groups arranged in the jet zone?

Answer 8

The loops are around the jet pipe and it runs along the 10th and 14th stage bleed air ducting in the pylon areas

Question 9

What are the two benefits of the dual loop detection systems?

Answer 9

Minimize false fire warnings. This is because both loops must sense for fire or overheat condition before a fire is detected.
The aircraft can be dispatched with a loop that is in operative and still provide fire and overheat protection.

Question 10

Explain the operation of the fire detection control unit.

Answer 10

This unit monitors the electrical resistance of the loops. Both loops must sense the same decrease in electrical resistance at the same time for the fire detection control unit to send a signal to the EICAS.

Question 11

What do the fire extinguisher bottles contain?

Answer 11

The bottles contained Halon and are pressurized with nitrogen

Question 12

Where are the engine fire extinguishers located?

Answer 12

The extinguishers are located in the aft equipment bay below the APU enclosure

Question 13

Will the left engine fire bottle only discharge into the left engine?

Answer 13

No, both bottles can be discharged into one engine. This is determined by which fire switch is pressed.

Question 14

What is the purpose of the FIRE DETECTION Control Panel?

Answer 14

To select a single loop if one has failed so the aircraft can be dispatched. The panel can also be used to test the fire and over heat detection system.

Question 15

What happens when the LH or RH FIRE PUSH switch light are pressed?

Answer 15

• Fuel feed SOV is closed
• Bleed air SOV is closed
• Hydraulic SOV is closed
• Engine driven generator is taken off-line
• Both fire extinguisher bottle squibs are armed, both BOTTLE ARMED PUSH TO DISCH switch lights illuminate.

Question 16

What happens when a BOTTLE ARMED PUSH TO DISCH switch light is pressed after being activated by the FIRE switch light?

Answer 16

And electrical current fires the squib on the selected bottle. The Halon is directed into the engine nacelle on the side of the selected fire switch.

Question 17

How many loops are used to detect a fire or overheat condition of the APU?

Answer 17

Two loops of the same design as an engine loops.

Question 18

What monitors the fire loops of the APU?

Answer 18

The fire detection control unit monitors the fire loops of the APU.

Question 19

How many squibs does the APU fire bottle have?

Answer 19

Two

Question 20

Where are the APU fire detection loops located?

Answer 20

The loops are around the inside of the APU enclosure.

Question 21

Where is the fire extinguisher bottle for the APU located?

Answer 21

It is located in the aft equipment bay, beside the APU enclosure.

Question 22

Where is the APU fire warning horn located?

Answer 22

The horn is located in the aft equipment bay under the APU battery.

Question 23

Explain the cargo smoke detectors?

Answer 23

Two smoke detectors are installed in the ceiling of the cargo compartment. As the name states, they monitor the compartment for the presence of smoke. If one or both detect smoke it will aluminate the CARGO SMOKE on the EICAS and all airflow will stop to the cargo bay.

Question 24

Is there any fire extinguishing in the lavatory?

Answer 24

Fire extinguishing is only provided in the waste bin

Question 25

Explain the fire extinguisher in the waste bin

Answer 25

there are two heat sensitive plugs that melt and release the halon into the bin. The bottle is located on a bracket beside the waste bin

Question 26

What detects an overheat condition in the main landing gear bay?

Answer 26

A single detection loop in the top of each wheel bin that is monitored by the overheat detection unit.

Question 27

How does the loop in the landing gear bay detect an overheat condition?

Answer 27

The loop has an outer metal cover with two internal wires separated by insulating material. As he is increased the resistance of the insulator decreases. At a certain point a signal will be sent to the Monitor and A overheat indication will be displayed.

Question 28

What will happen if the gear bay over heat detection loop fails?

Answer 28

The control unit continuously monitors the loop and if the loop is not working properly, and Amber E I CAS message MLG OVHT FAIL is presented.

Question 29

Explain the engine bottle switch position one and two on the firex monitor panel

Answer 29

The switch is used to check the serviceability of the squibs on engine bottles one and two.

Question 30

Where is fire detection and extinguishing provided?

Answer 30

Left and right engine nacelles, APU, and cargo areas. The lavatory has smoke detection with extinguishing in the waste bin.

Question 31

How can the fire bell on the flight deck be silenced?

Answer 31

By pressing the master warning switch light

Question 32

Which areas only have overheat detection?

Answer 32

The main wheelwells jet pipe and pylon areas

Question 33

How long does it take to completely discharge both cargo fire extinguisher bottles?

Answer 33

It takes a total of 45 minutes to discharge both bottles. One discharges over 45 minutes to maintain a level of Halon in the cargo compartment

Question 34

What would be the warning if there is a bleed air leak in the pylon?

Answer 34

The Warning would be a JET PIPE OVHT on the associated side