Amt 227

Question 1

What is amt 227

Answer 1

Engine fire protection system

Question 2

is the visible result of a rapid,
exothermic chemical reaction
called combustion, where a fuel source
reacts with an oxidizing agent, typically
oxygen, to produce heat, light, and flame.

Answer 2

Fire

Question 3

Other types of detectors in this
category include —————————– capable of
detecting combustible mixtures that can lead to
accumulations of explosive gases.

Answer 3

carbon monoxide detectors and
chemical sampling equipment

Question 3

is the visible result of a rapid,
exothermic chemical reaction
called

Answer 3

Combustion

Question 3

Because fire is one of the most
dangerous threats to an aircraft, the
potential fire zones of modern
multiengine aircraft are protected by a

Answer 3

Fixed Fire protection system

Question 4

Typical zones on aircraft that
have a fixed fire detection and/or
fire extinguisher system are:

Answer 4

Engine and auxiliary power unit
Cargo baggage and compartments
Lavotories on transport aircraft
Electronic bays
wheel wells
Bleed air ducts

Question 4

Fires are detected in reciprocating
engine and small turboprop aircraft
using one or more of the following:

Answer 4

Overheat detectors
Rate of temperature rise detectors
Flame detectors
Observation by crew members

Question 5

are better
suited to monitor areas where materials burn
slowly or smolder, such as cargo and baggage
compartments.

Answer 5

Smoke detectors

Question 6

A fire detection system should
signal the presence of a fire.
Units of the system are
installed in locations where
there are greater possibilities of
a fire.

Answer 6

Engine fire detection system

Question 6

Fire protection
following features
as possible:

Answer 6

1. No false warnings under any flight
   or ground condition.
2. Rapid indication of a fire and
   accurate location of the fire.
3. Accurate indication that a fire is
   out.
4. Indication that a fire has reignited.
5. Continuous indication for duration
   of a fire.
6. Means for electrically testing the
   detector system from the aircraft
   cockpit
7. Resists damage from exposure to oil,
   water, vibration, extreme
   temperatures, or handling.
8. Light in weight and easily adaptable
   to any mounting position.
9. Circuitry that operates directly from
   the aircraft power system without
   inverters.
   10.Minimum electrical current
   requirements when not indicating a
   fire.
   11.Cockpit light that illuminates,
   indicating the location of the fire,
   and with an audible alarm system.
   12.A separate detector system for each
   engine.

Question 7

Three detector system
types in common use are the

Answer 7

Thermal switch
Thermocouuple
Continuous loop

Question 7

system energizes indicator lights through
heat
-sensitive switches that close when
temperatures exceed a set limit, signaling
fire or overheat conditions [Figure 9
-1]. The
number of switches varies by manufacturer,
with some installations connecting all
detectors to one light and others assigning
separate switches to individual lights. Certain
warning lights are push
-to
-test, allowing bulb
and circuit checks via an auxiliary test relay.
The circuit in Figure 9
-1 also includes a
dimming relay, which adds a resistor to
reduce brightness, enabling multiple warning
lights to be dimmed simultaneously.

Answer 7

Thermal switch system

Question 8

Depends on rate of temperature rise.
Does not warn during slow overheating or
short circuits.

Answer 8

Thermocouple system

Question 8

System components of thermocouple system

Answer 8

Relay box, warning lights and thermocouples, detector unit, alarm circuit, test circuit

Question 9

• Con tains sensi tive relay, slave relay, and thermal tes t
  uni t .
• May include 1–8 iden tical ci r cui ts depending on fi re
  zones .
• Relays con trol wa rning ligh ts; thermocouples con trol
  relay opera tion .

Answer 9

Relay box

Question 9

• • Several thermocouples in series wi th ea ch o ther and
    wi th the sensi tive relay.
• • Leads made from me tals depending on tempera ture
    exposure:
• • Iron + cons tan tan or copper + cons tan tan (CHT
    measuremen t) .
• • Chromel + alumel ( turbine EGT thermocouples) .
• • Ho t junc tion: metals joined and exposed to fi re hea t .
• • Re ference junc tion ( cold junc tion): enclosed in dead
    ai r spa ce be tween insula tion blocks .

Answer 9

Circuit desgin

Question 10

• Thermocouple surrounded by a metal cage for
  durability without restricting air flow.
• Leads are installation-speci fic and must not be
  altered, or calibration is lost .

Answer 10

Mechanical protection

Question 11

• Rapid temperature rise → voltage produced due to
  di f ference between hot and re ference junctions.
• Gradual heating → both junctions heat equally →
  no voltage , no warning.
• Fire → hot junction heats faster → voltage causes
  current in detector circuit.

Answer 11

Voltage generation

Question 12

• Current > 4 mA (0 .004 A) → sensitive relay closes.
• Completes circuit to slave relay coil → slave relay
  closes → warning light illuminates.
  R

Answer 12

Relay operation

Question 13

• Number of thermocouples depends on
  fire zone size; total resistance ≤ 5
  ohms.
• Circuit [Figure 9-2] includes two
  resistors:
• Resistor across slave relay absorbs selfinduced voltage, preventing arcing at
  sensitive relay contacts.
• Protects fragile contacts from burning or
  welding.
• When sensitive relay opens, slave relay
  coil collapses → resistor provides current
  path → arcing eliminated.

Answer 13

Circuit resistance and resistors

Question 14

also known as flame de te c tors , a re designed to
trigger ala rms when they de te c t spe ci fic radia tion emissions
produced by hydrocarbon flames .

Answer 14

Optical fire detectttion systems

Question 15

two types of optical fire detection system

Answer 15

in frared ( IR) and ultraviolet

Question 16

These voltages are
ampli fied and processed by
electronic circuits designed
to match the time
signature o f hydrocarbon
flames while re jecting false
alarms from sources such
as incandescent lights or
sunlight.

Answer 16

optical fire detection system

Question 17

are based on the
principles of gas laws. The sensing
element consists of a closed heliumfilled tube connected at one end to a
responder assembly. As the element is
heated, the gas pressure inside the
tube increases until the alarm threshold
is reached.

Answer 17

Pneumatic thermal fire detection

Question 18

* Used almost exclusively on large commercial aircraft for powerplant fireprotection . * Provide supe rio r de te c tion pe r fo rman c e , b road coverage ,and proven ruggedness in ha rsh tu rbo fan envi ronm en ts .

Answer 18

Continuous loop detector systems

Question 19

* O f fe r mo re comple te cove rag e than spo t -typ e tempe ra tu r e de te c to rs . * Fun c tion as advan ced ve rsions o f the the rmal swi t ch sys tem . * Ope ra te as ove rhea t sys tems : hea t -sensi ti ve uni ts comple te ele c t ri cal ci r cui ts a t a se t tempe ra tu re . * Do no t have ra te-o f - t emp e ra tu r e-ris e sensi tivi t y

Answer 19

Continuous loop detector system

Question 20

two types of continuous loop detector system

Answer 20

Kidde continuous loop sysem and fenwal

Question 21

is built around a slender inconel tube that is packed with thermally sensitive eutectic salt and a nickel wire center conductor [Figure 9 -4]. These sensing elements are connected in series to a control unit, and they may be of equal or varying lengths, with identical or different temperature settings depending on the installation.

Answer 21

Fenwal continuous loop system

Question 22

Incorporates two wires embedded within an inconel tube that is filled with a thermistor core material [Figure 9-5] . Running the length o f the core are two electrical conductors: one is grounded to the tube , while the other connects to the fire detection control unit . As the core temperature rises, its electrical resistance to ground decreases.

Answer 22

Kiddie continuous loop system

Question 23

The system also distinguishes between an electrical short and a fire by analyzing the rate of resistance change.

Answer 23

Kidde continuous loop system

Question 24

give me the location of the fire zones

Answer 24

Engine fire extinguishing bottles Aircraft harness Apu fire detector Apu fire extinguishing bottles Engine fire detectors. main wheel well fire detectors Federated controllers Avionics bay smoke detectors

Question 25

The powerplant installa tion has several designa ted fire zones:

Answer 25

(1) the engine power section; (2) the engine accessory section; (3) except for reciproca ting engines , any comple te powerplan t compar tment in which no isolation is provided between the engine power section and the engine accessory section; (4) any APU compar tmen t; (5) any fuel-burning heater and other combus tion equipmen t installa tion; (6) the compressor and accessory sections o f turbine engines; and (7) combus tor, turbine , and tailpipe sections o f turbine engine installa tions that contain lines or componen ts carrying flammable fluids or gases.

Question 26

Common types of fire detector

Answer 26

Thermal Switch System – Thermocouple System – Optical (Flame) Detector – Pneumatic Thermal Detector – Continuous-Loop Systems –

Question 27

Common use for thermocouple

Answer 27

older aircraft, rate-of-temp-rise

Question 28

Common use for Smoke detectors

Answer 28

cargo & baggage compartments

Question 29

Common use for continuous loop system

Answer 29

large commercial aircraft engines

Question 30

Common use for Optical detectors

Answer 30

light turboprops & helicopters