FIRE PROTECTION Flashcards
(50 cards)
What do fire systems consist of?
- sensors
- control unit
- warning panels
What is a spot sensor?
Bi-metallic sensor, triggers alarm when closes.
Used for pneumatic duct leak detection
What are fire and overheat sensors?
Continuous loops
Monitor large areas
What is a pneumatic pressure loop? (Systron or donner loop)
A sealed tube which contains gas. When gas expands at higher temp, operates pressure switch (responder)
Each loop contains a semiconductor material. What is the purpose of this?
Decreases electrical resistance with increasing temp. Alarm sounds if resistance between central wire and tube decreases below value
What does a control unit identify?
Identifies the normal and alarm conditions of a sensor with a measurement of resistance.
If a fire is detected, what will the central warning system activate?
Red fire master warning lights, aural warning and a message on the ECAM/EICAS display.
How do you cancel a warning in the cockpit?
Pressing the master warning light
Failure with a bi-metallic switch in the open and closed position causes what?
Open - prevents overheat and fire detection
Closed - false alarm
What advantage do other sensors have over bi-metallic sensors?
Prevention of false fire warning and triggers fault message
What are all essential fire warning systems?
Dual loop systems
2 sensors and detection circuits in the control unit
On a dual loop system, when will the alarm be triggered?
When both sensors detect fire at the same time
Prevents false indication
If the control unit detects a faulty sensor, how do dual loop systems detect fire?
Automatic switching allows the sensor to trigger the warning off just one sensor.
(Message about faulty one on the central warning display)
When should operational checks of the fire system be carried out?
Before engine and APU starts.
How can you find out which sensor is faulty in a system?
Via the central maintenance computer.
What is a semi conductor loop?
Stainless steel tube with semiconductor ceramic material with a wire in the centre
What is the function of the ceramic material in a semiconductor loop?
Acts like endless resistors which have NTC characteristics
On the semiconductor loop which contains 2 internal wires, what is each wire for?
Upper - connected to control unit
Lower - connected internally to ground
(Kiddle loop)
If more than one loop is required and loops are connected, what does this mean?
Resistors are connected In parallel
What is the resistance between for longer and shorter loops?
1 mega ohm for long loops and 10 mega ohm for shorter.
How is dual loop failure made almost impossible?
The closed loop condition is tested during operational tests.
How is a short circuit created?
Rubbing between the structure and loop, causing contact with the internal wire.
What resistance will fire/overheat warnings occur?
500 ohms
In an essential system, how is false alarming from short circuiting protected?
Prevention via the dual loop system.
