11.8 Flashcards
Whats the three things required for a fire to start ?
Fuel
Heat
Oxygen
What should fire zones be equipped with ?
Detection and extinguishing equipment.
Whats the fire zones ?
APU and engines
Baggage
Toilet
Electronic components
Wheel wells
Bleed air ducts
What should detectors not automatically do ?
Should not Operate extinguisher
Whats the 3 common fire detection systems ?
Thermal switches
Thermo couple
Loop sensing elements - most used
Explain the thermal switch system used in an aircraft to detect fire ?
Heat sensitive switches which complete a circuit at a certain temp which elominates warning lights.
( presence of a relay allows you to test the warning system )
Explain a continuous loop system used to detect a fire ?
Two types =
Fenwal system - when an overheat condition occurs at any point along the element length, the resistance of the salt drops sharply causing a current to flow between the outer sheath and the centre conductor. Current flow is sensed by control unit which produces a signal to activate the alarms. Once fire s extinguished, fenwal system returns to standby
Kiddle system - has two wires embedded in a inconel tube filled with thermistor core material. One conductor has ground connection to the tube and the other one connects to the fire detection control unit. As the temp of core increases, electrical resistance to the ground decreases. When fire is extinguished, resistance increases again and grounds warning system.
Whats the three fire detectors ?
Thermal switch
Thermocouple
Continuous loop
Note - fenwal system has one electrode whereas a Kidde system has 2
Explain dual - loop system ?
Two complete basic fire detection system with connected outputs meaning both must signal to result in a fire warning.
( increase reliability in false fire warnings )
Explain a pneumatic continuous loop system ?
-Contained gas ( helium ) expanding due to the application of heat.
-designed so that damage to sensor tube cannot result in a false alarm.
Whats the two sensing functions for a pneumatic continuous loop system ?
=Overall average temp - activated from expansion of helium gas inside detector
=Localised discrete temp increase \that was cause by flame or hot gas - hydrogen filled core material which releases hydrogen whenever part of the tube is heated for at least 5 seconds.
What are continuous lop systems passed trough to minimise abrasion ?
Rubber grommets
( must be installed on the sensing element )
Explain smoke detection system ?
Air is continually sampled into smoke detection system, any smoke found in sample causes a change in current flow. This change in current will trigger alarm
Whats the two types of smoke detector systems ?
Photoelectric
Ionisation type
What does the cargo smoke detector system consist of ?
Light emitting diodes
How many passengers should an aircraft carry for a requirement for it to instal a lavatory smoke detector system ?
20 or more
( if smoke is detected the lavatory master call light flashes and gives warning to flight attendant station. )
Whats the 4 areas on a aircraft which a fire extinguishing system is installed ?
- engines
- APU
- baggage and cargo compartment
- lavatories
( must me manually controlled )