General Authority of Civil Aviation (GACA) Aeronautical Information Publication (AIP) Practice Exam

What is a possible cause for the trim air "FAULT" light to illuminate?

1. The trim air switch is manually turned off

2. The cabin pressure is too high

3. The recirculation fans are malfunctioning

4. The external temperature sensor is faulty

The correct answer is: The trim air switch is manually turned off

The trim air "FAULT" light illuminating can indeed be caused by the trim air switch being manually turned off. This switch controls the flow of warm air used for cabin temperature control, and when it is disengaged, it indicates to the aircraft's systems that there is a failure in the trim air system, thus triggering the fault light. This is an important safety feature that alerts the crew to a potential lapse in cabin comfort controls. In contrast, while high cabin pressure, malfunctioning recirculation fans, or faulty external temperature sensors can affect the environment in the cabin, they do not directly correlate with the trim air system's operational status in the same manner. High cabin pressure usually results from incorrect pressurization management rather than a fault in the trim air system. Malfunctioning recirculation fans may lead to inadequate airflow but would not activate the trim air "FAULT" light. Lastly, issues with the external temperature sensor would affect readings and possibly other systems but wouldn't directly cause the trim air light to illuminate unless indirectly influencing the trim air system's performance.