Fire Detection/Extinguishing Systems Flashcards
How many sensors are there, and where are they?
5, Two in each engine compartment and one in the APU compartment.
How do the sensors work?
When one of the sensors detects infrared radiation (fire) and no blue light (sunlight), it sends a signal to the associated control amplifier. The control amplifier then activates both master warning panel FIRE lights and the proper T-handle lights.
new vs old sensors?
Older cadmium sulfide optical detectors are susceptible to sunlight filtered through smoke or haze, or at sunrise or sunset, and may trigger the flame detectors and cause a false fire indication. Newer IR flame detectors are designed to eliminate susceptibility to false alarms.
When testing the system, what does the number 1 position do?
In the 1 position, the continuity of the three firewall mounted detectors (No. 1 engine, No. 2 engine, and the APU) is checked. Normal indications include two master warning panel FIRE lights and all three T handles illuminated.
When testing the system, what does the number 2 position do?
In the 2 position, the continuity of the two engine deck mounted detectors is checked. Normal test indications include two master warning panel FIRE lights and both engine T-handles illuminated.
Note about new IR sensors and lights
Aircraft configured with newer IR flame detectors will result in up to 5 second delay in T-handle lights extinguishing following FIRE DETR TEST knob movement.
General info on the fire bottles
The system includes two bottles that are filled with Halon and charged with nitrogen. compartment. Both containers have dual outlets with their own firing mechanism. Each container has a pressure gauge and a thermal discharge relief port. Thermal discharge is indicated by the loss of the red plastic disc on the left side of the aircraft.
How do the ENG T-Handles work?
Pulling aft on the T-handle arms the system and mechanically places the fuel selector in the OFF position. The fire-extinguisher logic module determines which CADS to fire and into which compartment to discharge the fire extinguishing agent based upon actuation of the T-handles and fire-extinguisher switch.
What happens if the #1 T-handle and the APU T-handle are actuated at the same time?
When both the No. 1 Engine and APU T-handles have been actuated, the fire-extinguishing agent will be discharged into the compartment for the T-handle that was last actuated.
What does the APU T-handle do?
When pulled, the APU T-handle removes electrical power from the APU airframe fuel shutoff valve, allowing it to close. Pulling the APU T handle also removes power from the prime boost pump, sends a stop signal to the ESU/DESU, arms the fire extinguisher system, and positions the extinguisher directional control valve to the APU compartment
What if you have no AC power?
the RESERVE position must be used to discharge the agent into the APU or No. 1 engine compartment. The No. 2 engine compartment has no fire extinguisher capability without ac power available.
Note about multiple T-handles actuated at the same time.
When ac power is available, activation of multiple T-handles may result in both bottles being fired at the same time, leaving no reserve capability.
Impact Switch Operation
A multiple-axis impact (10g) sensor is hard-mounted to the airframe. When crash impact forces are detected, the switch is activated via power from the Battery Utility bus, discharging one fire bottle into each engine compartment.
