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M15 > FIRE PROTECTION > Flashcards

FIRE PROTECTION Flashcards

1
Q

What do fire systems consist of?

A
  • sensors
  • control unit
  • warning panels
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2
Q

What is a spot sensor?

A

Bi-metallic sensor, triggers alarm when closes.

Used for pneumatic duct leak detection

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3
Q

What are fire and overheat sensors?

A

Continuous loops

Monitor large areas

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4
Q

What is a pneumatic pressure loop? (Systron or donner loop)

A

A sealed tube which contains gas. When gas expands at higher temp, operates pressure switch (responder)

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5
Q

Each loop contains a semiconductor material. What is the purpose of this?

A

Decreases electrical resistance with increasing temp. Alarm sounds if resistance between central wire and tube decreases below value

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6
Q

What does a control unit identify?

A

Identifies the normal and alarm conditions of a sensor with a measurement of resistance.

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7
Q

If a fire is detected, what will the central warning system activate?

A

Red fire master warning lights, aural warning and a message on the ECAM/EICAS display.

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8
Q

How do you cancel a warning in the cockpit?

A

Pressing the master warning light

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9
Q

Failure with a bi-metallic switch in the open and closed position causes what?

A

Open - prevents overheat and fire detection

Closed - false alarm

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10
Q

What advantage do other sensors have over bi-metallic sensors?

A

Prevention of false fire warning and triggers fault message

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11
Q

What are all essential fire warning systems?

A

Dual loop systems

2 sensors and detection circuits in the control unit

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12
Q

On a dual loop system, when will the alarm be triggered?

A

When both sensors detect fire at the same time

Prevents false indication

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13
Q

If the control unit detects a faulty sensor, how do dual loop systems detect fire?

A

Automatic switching allows the sensor to trigger the warning off just one sensor.
(Message about faulty one on the central warning display)

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14
Q

When should operational checks of the fire system be carried out?

A

Before engine and APU starts.

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15
Q

How can you find out which sensor is faulty in a system?

A

Via the central maintenance computer.

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16
Q

What is a semi conductor loop?

A

Stainless steel tube with semiconductor ceramic material with a wire in the centre

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17
Q

What is the function of the ceramic material in a semiconductor loop?

A

Acts like endless resistors which have NTC characteristics

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18
Q

On the semiconductor loop which contains 2 internal wires, what is each wire for?

A

Upper - connected to control unit
Lower - connected internally to ground
(Kiddle loop)

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19
Q

If more than one loop is required and loops are connected, what does this mean?

A

Resistors are connected In parallel

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20
Q

What is the resistance between for longer and shorter loops?

A

1 mega ohm for long loops and 10 mega ohm for shorter.

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21
Q

How is dual loop failure made almost impossible?

A

The closed loop condition is tested during operational tests.

22
Q

How is a short circuit created?

A

Rubbing between the structure and loop, causing contact with the internal wire.

23
Q

What resistance will fire/overheat warnings occur?

A

500 ohms

24
Q

In an essential system, how is false alarming from short circuiting protected?

A

Prevention via the dual loop system.

25
Q

What are the number of discharge heads on a fire extinguisher equal to?

A

Number of compartments a bottle must supply.

26
Q

How much explosive does the discharge cartridge in the centre of the discharge head contain?

A

Around 400 milligrams.

Class C explosives.

27
Q

When does the power explode in a discharge cartridge?

A

When an electric current heats up a wire (the squib) inside the cartridge.

(Sparks can accidentally explode the device)

28
Q

What is the maximum service life of the discharge cartridge?

A

6 years.

29
Q

What is the date on the cartridge bottle?

A

Date of manufacture.

10 years maximum storage and service life.

30
Q

What does a pressure switch do on a bottle?

A

Sends indications to cockpit if level falls between 50%.

31
Q

Why would the temp in the bottle area increase?

A

Broken pneumatic duct near bottle or a fire.

Overpressure used as pressure will increase with temp

32
Q

When does the frangible disc break in the bottle?

A

When pressure increases to 1700 psi.

3 times normal pressure

33
Q

What has happened if a red disc is missing from the fuselage?

A

Fire bottles have over pressured and halon has been released overboard.

(Missing yellow disc near red disc of bottle discharges via spray nozzles)

34
Q

Is the APU fire system automatic or manual?

A

Automatic.

35
Q

What pushes the halon out of the bottle?

A

Pressure nitrogen.

36
Q

How is the hot battery bus always powered?

A

Batteries. (Power source always available)

37
Q

Why is a broken squib extremely bad?

A

The extinguishing bottle can no longer be used.

38
Q

What happens when you test the squib?

A

Very small current sent through, small enough to not fire off the bottle.

39
Q

What is a “2 shot system”?

A

2 fire bottles can be discharged into one engine.

40
Q

When would a second bottle be discharged?

A

If the fire has not gone out after 30 seconds.

41
Q

Where is only a “one shot” system used?

A

APU.

42
Q

When does the APU fire bottle release when the APU fire warning is activated?

A

3 seconds after automatically.

43
Q

What are the installation limits for loops?

A

Max bending of no more than 3.2mm

Min radius of 25.4 mm

44
Q

Gas pressure inside a gas loop is what in comparison to the ambient pressure at sea level?

A

2 times Higher

45
Q

How do you know if the pressure switch is open or closed on a gas loop?

A

With the resistor inside the responder

46
Q

In a gas loop, when pressure will shut the pressure switch?

A

High pressure

47
Q

What does an extinguisher bottle consist of?

A

Halon 1301 in liquid format pressurised with nitrogen at 600psi

48
Q

Where are 20kg extinguisher bottles used?

A

Cargo compartment, largest bottle

49
Q

Where are 10kg extinguisher bottles used?

A

Engines

50
Q

Where are 5kg extinguisher bottles used?

A

APU

M15 (18 decks)

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