FAA Flight Instructor Airplane (FIA)Aircraft Systems and InstrumentsMedium
A pilot begins a rapid descent from cruise altitude by significantly reducing engine power. To help prevent engine damage during this descent, what should the pilot do regarding the cowl flaps?
- AOpen the cowl flaps fully to maximize cooling airflow
- BLeave the cowl flaps in the cruise position regardless of power change
- CClose the cowl flaps to help retain engine heat and prevent shock cooling
- DCycle the cowl flaps rapidly open and closed throughout the descent
Show answer & explanationAnswer & explanation
Correct answer: C. Close the cowl flaps to help retain engine heat and prevent shock cooling
A rapid power reduction combined with descending into denser, cooler air can cause cylinder head temperatures to drop too quickly, leading to shock cooling and potential cracking of cylinders. Closing the cowl flaps reduces cooling airflow, helping the engine cool more gradually and evenly.
Why the other options are wrong
- A. Opening the flaps increases cooling airflow, worsening the shock-cooling risk.
- B. Leaving flaps unchanged fails to address the increased cooling from reduced power and higher airspeed in descent.
- D. Rapid cycling provides no benefit and can distract from other descent tasks.
Cowl Flaps
Adjustable panels that control airflow through the engine compartment to regulate cylinder head temperature; typically open for climb/high power and closed for cruise/descent.
- Open increases cooling airflow (used in climb, ground ops)
- Closed reduces cooling airflow and drag (used in cruise, descent)
- Closing during descent helps prevent shock cooling from rapid temperature drop
Memory trick: Descend and close — keep the engine cozy, not shocked.