Downwash from the propeller to the horizontal tail is called which effect?

• A. Power effect
• B. Propeller effect
• C. Dihedral effect
• D. Keel effect

Answer: (B)

The phenomenon is the propeller effect. The spinning propeller creates a wake that flows onto the horizontal tail, changing the tail’s angle of attack and thus its lift. This alters the pitching moment and trim of the airplane as power changes. In essence, the tail is being influenced by the propeller’s induced flow, so the effect is specifically tied to the propeller’s influence on the airflow—hence the name.

This isn’t about the wing’s dihedral or the fuselage behaving like a keel, and it’s distinct from any general “power” stability effects that aren’t tied to the propeller’s induced flow onto the tail.