Answers - Engine Fire Protection Systems

1. c
A typical fire detection system used in reciprocating engine aircraft incorporates a thermocouple system that uses a series of rate-of-temperature-rise detectors. With this type of system a warning will not sound when an engine warms up slowly or when a short circuit develops. However, if temperatures in the engine compartment should rise rapidly, such as when a fire exists, the detectors will sound a warning horn in the cockpit.

2. b
The function of a fire detection system is to activate a warning device in the event of a powerplant fire. It is important to remember that a fire detection system only warns the pilot of a fire,

3. c
Since the question specifies a temperature of 75°C you must interpolate between the minimum and maximum limits for both 70°F and 80°F. To interpolate find the difference between the two readings, divide the difference by two and add the quotient to the lower pressure. The minimum container pressure at 70°F is 31 9 psig and 356 psig at 80°F. Therefore, the minimum pressure at 75°F is 338 psig (356 - 319 = 37 ÷ 2 = 18.5 + 319 = 337.5). The maximum pressure at 70°F is 405 psig and 443 psig at 80°F. Therefore, the maximum pressure at 75°F is 424 psig (443 - 405 = 38 ÷ 2 = 19 + 405 = 424).

4. a
In a turbine engine powered aircraft, the fire extinguishing portion of a fire protection system typically includes a cylinder of extinguishing agent for each engine and nacelle area. The container of agent is normally equipped with two discharge valves that are operated by electrically discharged cartridges. The electrical current needed to discharge the cartridges is released by the fire handles in the cockpit.

5. a
When liquid CO, leaves the fire extinguisher nozzle under pressure, it converts into a gas that extinguishes flame by displacing the oxygen around the flame and smothering it.

6. a
The nitrogen charge within a typical high rate of discharge container is retained, or held in by a discharge plug and a safety discharge connection. The discharge plug is sealed with a breakable disk combined with an explosive charge that is electrically detonated to discharge the contents of the bottle. The safety discharge connection, or fusible disk, is capped at the inboard side of the engine strut with a red indication disk. If the temperature rises beyond a predetermined safe value, the disk will rupture, dumping the agent overboard.

7. b
A continuous-loop fire detection system consists of a loop of one or two conductors installed around an engine compartment that, when overheated, sends electrical current to a warning indicator in the cockpit.

8. c
Spot detector fire detection systems consist of a bimetallic thermoswitch installed between two loops of wire. When the thermoswitch is heated to a predetermined temperature, the switch closes and completes the circuit between the two wire loops. With the circuit completed, electrical current flows to the fire warning horn in the cockpit.

9. c
In a typical engine fire extinguishing system, the extinguishing agent is distributed through spray nozzles and perforated tubing. The perforated tubing distribution system is more common with reciprocating engines, while spray nozzles are typically used with turbine engines.

10. c
Bromotrifluoromethane (Halon 1301) is one of the most effective fire extinguishing agents. In addition, it is non-toxic and non-corrosive. Both answers (A) and (B) are wrong because Halon 1202 and Halon 121 1 are more toxic than Halon 1301. Furthermore, Halon 1202 can be corrosive.

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