What does direct drive mean in the engine description?

• A. The propeller is connected directly to the crankshaft without reduction gears.
• B. The engine uses a reduction gearbox.
• C. The propeller is variable pitch.
• D. The engine is turbocharged.

Answer: (A)

Direct drive means the propeller is connected straight to the engine’s crankshaft with no reduction gears in between. In this setup, the propeller spins at roughly the same speed as the engine, because there’s no gearbox to slow the propeller down or speed it up relative to the engine. This contrasts with configurations that use a reduction gearbox, which keeps the propeller at a more efficient RPM by turning it slower than the engine. The other terms—variable pitch and turbocharging—describe blade angle and intake air density, respectively, and don’t define how power is transmitted from the engine to the propeller.