How many fire detectors are mounted in each engine compartment to indicate an external engine fire?

• A. 2
• B. 3
• C. 4
• D. 5

Answer: (B)

Three fire detectors are mounted in each engine compartment. Having multiple detectors provides redundancy so a single faulty sensor won’t cause a false or missed warning. The system is designed to indicate an external engine fire when two of the three detectors sense fire, giving a reliable indication while avoiding nuisance alarms. The other counts either don’t provide enough redundancy or aren’t how this setup is specified, so three is the correct configuration for indicating an external engine fire.