Which fan(s) will the crew be directed to select to OVRD when the smoke configuration needs to be set?

Which fan(s) will the crew be directed to select to OVRD when the smoke configuration needs to be set?

• A. BLOWER only
• B. EXTRACT only
• C. None
• D. Both the BLOWER and EXTRACT fans

Answer: (D)

In a smoke situation, you want to move air out of the affected areas and replace it with clean air as quickly and predictably as possible. Overriding the ventilation fans gives you deterministic control over airflow, bypassing automatic limits that might reduce purge speed when smoke is present. The BLOWER handles recirculated cabin air, while the EXTRACT fan expels air overboard. By selecting both to OVRD, you ensure the system actively moves air through the cabin and cockpit and out of the aircraft, maximizing smoke removal rather than relying on automatic sequencing. This coordinated override is essential to purge smoke quickly and minimize contamination in the crew area. Choosing only one fan would not provide the full purge action—recirculating without expelling or expelling without sufficient supply doesn’t clear the smoke efficiently. Not overriding the system at all could allow automatic controls to limit airflow during a smoke event. Hence, both fans in override is the best approach.

In a smoke situation, you want to move air out of the affected areas and replace it with clean air as quickly and predictably as possible. Overriding the ventilation fans gives you deterministic control over airflow, bypassing automatic limits that might reduce purge speed when smoke is present.

The BLOWER handles recirculated cabin air, while the EXTRACT fan expels air overboard. By selecting both to OVRD, you ensure the system actively moves air through the cabin and cockpit and out of the aircraft, maximizing smoke removal rather than relying on automatic sequencing. This coordinated override is essential to purge smoke quickly and minimize contamination in the crew area.

Choosing only one fan would not provide the full purge action—recirculating without expelling or expelling without sufficient supply doesn’t clear the smoke efficiently. Not overriding the system at all could allow automatic controls to limit airflow during a smoke event. Hence, both fans in override is the best approach.