Why is a propeller blade twisted along its length?

A propeller blade is twisted along its length primarily to maintain a constant angle of attack from root to tip of the blade. This design feature is crucial in ensuring efficient airfoil performance across the entire span of the blade because different sections of the blade experience varying flow speeds.

At the root, where the blade is attached to the engine, the rotational speed is lower than at the tip. As a result, a higher angle of attack is needed at the root to produce sufficient lift, while at the tip, where airflow is faster, a lower angle is more appropriate. By incorporating twist into the blade design, manufacturers can ensure that each section of the propeller operates at its optimal angle of attack for maximum efficiency and thrust generation, thus enhancing overall performance.

The other options focus on different characteristics that do not directly explain the purpose of the twisting feature in propeller blades. For instance, while compensating for the centrifugal twisting moment is a consideration in propeller design, it is not the primary reason for the blade's twist. Similarly, while thrust is involved at various points along the blade, the objective is specifically about optimizing the angle of attack rather than merely increasing or maintaining thrust levels.