Flashcards in Powerplant Chapter 11 Deck (17)
What type of fire detector systems are used for engine fire detection?
Overheat, rate of rise, and flame detectors.
How does a thermal switch fire protection system operate?
When heated past a predetermined temperature, the switch closes causing the warning devices in the cockpit to activate.
How many thermal switches are needed in a thermal switch fire protection system?
At least one.
What kind of fire detection system allows more complete coverage than a spot-type system?
A continuous loop system.
What happens if an engine equipped with a thermocouple fire warning system overheats slowly?
Nothing, because a fast temperature rise or rapid heating is required for this type of fire system to operate.
What electrical power is required for a thermocouple fire protection system to operate?
Both the thermocouple-produced power and the aircraft electrical system are required for this type of fire protection system to operate.
What is the likely cause of a false fire warning?
The engine fire sensing loop is bent or kinked excessively.
What are fire extinguishing systems designed to do?
They are designed to dilute the oxygen levels around the engine to a points that does not allow combustion, or to reduce temperature below the ignition point.
Describe how a Kidder and Fenwal Continuous loop fire protection system functions.
A Kiddle system has a sensing element consisting of a sealed Inconel tube containing two conductors that are embedded in a thermistor material. One wire is electrically grounded to the outer tube at each end and acts as an internal ground, and the other is a positive lead. When a fire or overheat occurs, the resistance of system uses a sensing element consisting of a small diameter flexible Inconel tube containing a single wire electrode surrounded by ceramic beads. These ceramic beads prevent the electrode and tube from touching each other. Current is applied to the electrode while the outer tube is grounded to the aircraft structure. When a fire or overheat occurs, the core resistance of the ceramic beads drops, allowing current to flow between the center electrode and ground, energizing the alarm system.
What elements must be present for a fire to occur?
An ignition source such as heat or a spark, fuel and oxygen.
What group of fire extinguishing agents are no longer manufactured because of environmental concerns?
Halons (or Freon or chlorofluorocarbons [CFCs]) were no longer manufactured after 1995. However existing stocks of CFC may still be used and are subject to strict handling and disposal regulations.
How are fire extinguishing agents distributed?
Through perforated tubing and/or discharge nozzles.
What is the purpose of the discharge cartridge and how is it activated?
The discharge cartridge, or squib, which is electrically ignited, fires a projectile into the frangible disk, thereby releasing fire extinguishing agents.
How is a fire extinguisher system with a high rate of discharge classified?
As an HRD fire extinguisher system.
What do the red and yellow discs in a fire extinguishing system indicate?
A yellow disc indicates a normal discharge. A red disc indicates a thermal discharge.
How is the fire extinguishing agent in an HRD system distributed, and how long does it take to discharge?
The agent is distributed through a series of high pressure tubes and takes one to two seconds to discharge.