How many fire detectors are installed on each engine?

• A. 2
• B. 3
• C. 4
• D. 5

Answer: (B)

Fire detection coverage around an engine needs multiple detectors to catch a developing fire quickly and to stay reliable even if one detector has a fault. Placing three detectors in distinct zones around the engine covers the most likely fire locations: the crankcase area where oil fires can start, the fuel/lubrication side where leaks or vapor buildup can occur, and the exhaust or hot-turbo area where high temperatures can ignite flammable vapors. With three detectors, a fire must trigger more than one detector or be detected in one of several critical spots, which speeds warning and allows faster shutdown and response. Having only two detectors risks a blind spot where a fire could grow before being detected; adding more than three typically yields diminishing returns for the added cost and complexity. So, three detectors per engine balance effective coverage and reliability.