FAA Powerplant Written Practice Test

If a continuous loop fire detection system gives a false alarm, how can you determine if the problem lies in the control unit or the sensing loop?

1. By disconnecting the loop from the control box and observing if the false alarm stops

2. By testing the voltage across the sensors

3. By replacing the control unit

4. By visually inspecting the connection points

The correct answer is: By disconnecting the loop from the control box and observing if the false alarm stops

If a continuous loop fire detection system is giving a false alarm, disconnecting the loop from the control box and observing whether the false alarm stops provides insight into the source of the problem. When the loop is disconnected, the system should no longer receive signals from the sensing elements. If the false alarm ceases, this indicates that the issue is not in the control unit, but likely exists within the sensing loop itself. Conversely, if the false alarm persists even after disconnection, it suggests that the control unit may be malfunctioning or incorrectly interpreting the signals, thereby providing useful information for troubleshooting. This method effectively isolates the components and helps technicians narrow down where the fault might be originating. Testing the voltage across the sensors may provide useful information about the operational status of the sensors but does not directly confirm where the fault lies. Replacing the control unit may solve the immediate issue but does not address the root cause and could lead to unnecessary part replacement if the sensing loop is the actual culprit. Meanwhile, visually inspecting the connection points may help identify physical issues, but it does not allow for definitive conclusions about the presence of an ongoing false alarm in relation to the loop or control unit.