11 Engine Fire Protection

Question 1

1. What types of fire detector systems are used for engine fire detection?

Answer 1

Overheat, rate of rise, and flame detectors.

Question 2

2. How does a thermal switch fire protection system operate?

Answer 2

When heated past a predetermined temp, the switch closes causing the warning devices in the cockpit to activate.

Question 3

3. How many thermal switches are needed in a thermal switch fire protection system?

Answer 3

At least one.

Question 4

4. What kind of fire detection system allows more complete coverage than a spot type system?

Answer 4

A continuous loop.

Question 5

5. What happens if an engine equipped with a thermocouple fire warning system overheats slowly?

Answer 5

Nothing because a fast temp rise or rapid heating is required for this type of fire system to operate.

Question 6

6. What electrical power is required for a thermocouple fire protection system to operate?

Answer 6

Both the thermocouple produced power and the aircraft electrical system are required for this type of fire protection system to operate.

Question 7

7. What is the likely cause of a false fire warning?

Answer 7

The engine fire sensing loop is bent or kinked excessively.

Question 8

8. What are fire extinguishing systems designed to do?

Answer 8

To dilute the oxygen levels around the engine to a point that doesn’t allow combustion, or to reduce temps below the ignition point.

Question 9

9. Describe how a Kidde and Femwal continuous loop fire protection system functions.

Answer 9

A Kidde system has a sensing element consisting of a sealed Inconel tube containing 2 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.

Question 10

10. What elements must be present for a fire to occur?

Answer 10

An ignition source such as heat or spark, fuel, and oxygen.

Question 11

11. What group of fire extinguishing agents are no longer manufactured because of environmental concerns?

Answer 11

Halons were no longer manufactured after 1995.

Question 12

12. How are fire extinguishing agents distributed?

Answer 12

Through perforated tubing or discharge nozzles.

Question 13

13. What is the purpose of the discharge cartridge and how is it activated?

Answer 13

Electrically ignited and fires a projectile into the frangible disk, thereby releasing fire extinguishing agent.

Question 14

14. How is a fire extinguisher system with a high rate of discharge classified?

Answer 14

As an HRD fire extinguisher system.

Question 15

15. What do the red and yellow discs in a fire extinguishing system indicate?

Answer 15

Yellow = normal
Red = thermal

Question 16

16. How is the fire extinguishing agent in a HRD system distributed and how long does it take to discharge?

Answer 16

A series of high pressure tubes and takes 1-2 seconds to discharge.

Question 17

17. What is the purpose of a pressure gauge in a fire extinguishing system?

Answer 17

Indicates pressure within the container. To check if pressure is within limits, a pressure temp chart is used.