15.20 Flashcards
What type of detectors uses for engine fire or overheat detection
Continuous loops
What are the two types of continuous loop system
Semi conductor
Pneumatic pressure loop
What are the names for pneumatic loops
Systron and donner
How does a pneumatic. Pressure loop work
Contains gas sealed within the tube and when the pressure of gas increases at high temps a pressure switch is operated which triggers the alarm
How’s a semiconductor loop detector work
Each tube contains a semiconductor material and the material decreases in electrical resistance with rising temp and an alarms triggered when the resistance is below a certain threshold
What condition is normal for resistance on a control unit and what condition is normal for resistance in a alarm condition
High resistance for normal
Low resistance for alarm condition
How’s a central warning cancelled
By pressing master warning light
What’s the functions of all fire detection control units
Testing
Identify faults
Receive electrical signals from sensors and alarm normal or alarmed position
What type of system do all essential fire warning system have and how many sensors do they have
Dual loop
Two sensors
What’s the purpose of two sensors of the dual loop systems
To prevent a false warning
What happens if there’s a failure dual sensor/channel failure in a dual loop system
System Won’t operate and must be repaired before next flight
When must an operational check of fire detection test
Before each engine or APU start
What’s semiconductor material is filled within the centre of the semiconductor loop resistor and what does this act as
Ceramic sms adds as an endless number of resistors
What characteristic do semiconductor loops work off
Negative temp coefficient
What’s done to prevent the situation a fire which cannot be detected due to an open loop
End of loop is connected to the beginning to form a closed loop
