What percentage of engine torque is absorbed by the propeller?

• A. 80%
• B. 20%
• C. 90%
• D. 50%

Answer: (A)

When a piston or turbine engine drives a propeller, the torque the engine supplies is used to overcome the propeller’s aerodynamic load plus some mechanical losses. In normal propeller operation the propeller takes the vast majority of that torque, with the rest being consumed by the drivetrain and other accessories. A common rule of thumb is that about 80% of the engine torque is absorbed by the propeller. That means most of the engine’s twisting force goes into turning the propeller to produce thrust, while roughly 20% goes to losses in the gearbox, bearings, cooling, and other parasitic loads. The other percentages would imply a much different balance of load and losses and are not typical for this scenario.