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

What is the function of recirculation fans in an aircraft?

1. To assist the packs in maintaining a constant ventilation rate through the cabin

2. To increase the altitude of the aircraft

3. To reduce engine noise during flight

4. To elevate cabin pressure during ascent

The correct answer is: To assist the packs in maintaining a constant ventilation rate through the cabin

Recirculation fans play a crucial role in an aircraft's environmental control system, specifically in maintaining comfortable cabin conditions. Their primary function is to circulate air within the cabin, ensuring that the ventilation rate remains constant. By drawing in air from the cabin, the recirculation fans help to mix this air with freshly conditioned airflow provided by the air conditioning packs. This mixing is essential for maintaining uniform temperature and air quality throughout the aircraft’s cabin. The other options pertain to functions not associated with recirculation fans. For instance, increasing the altitude of the aircraft is managed by the engines and control surfaces, not by cabin air systems. Similarly, reducing engine noise during flight is primarily addressed through aircraft design and soundproofing materials rather than through the activity of recirculation fans. Elevating cabin pressure during ascent is a function of the pressurization system, which manages the cabin environment as the aircraft climbs. The operation of the recirculation fans is thus integral to ensuring a comfortable and safe environment for passengers and crew, aligning perfectly with the function described in the correct choice.