Which of the following is a common cause of intermittent fire detector alarms?

• A. Intermittent short in the detector system wiring
• B. Loose cargo in the aircraft
• C. Engine misfire in the engine
• D. Ground loops in the electrical system

Answer: (A)

Intermittent fire detector alarms are usually caused by a fault in the detector wiring rather than in the sensing element itself. A short that comes and goes in the detector circuit can create fluctuating signals that trigger the alarm sporadically, especially as the aircraft experiences vibration, temperature changes, or connector wear. In practice, wiring faults such as intermittent shorts or loose connections in the detector loop are a common, repeatable source of those erratic alarms because they directly disturb the electrical conditions the detector relies on to determine normal versus abnormal status.

Loose cargo isn’t a typical factor for the detector’s electrical sensing circuit, engine misfire doesn’t affect the fire-detecting circuitry, and while ground loops can cause electrical noise in some systems, they’re not the most common cause of intermittent fire detector alarms in standard installations.