What effect does a zero blade angle have on a propeller?

A zero blade angle on a propeller means that the blades are aligned straight with the airflow, effectively capturing no air to create lift or thrust. In this position, the angle of the blades does not deflect the oncoming air in a way that would allow the propeller to generate thrust. Instead, the propeller acts more like a disk, cutting through the air without pushing it backward to produce forward motion.

In contrast, positive thrust would occur at a certain angle where the blades can push air back effectively. Generating reverse thrust requires a different blade angle, typically negative, that allows the blades to pull air forward and push the aircraft backward. Minimizing drag generally involves positioning the blades in such a way that they optimize aerodynamic efficiency, which is not achieved at a zero blade angle. Hence, with a zero blade angle, the propeller neither provides forward thrust nor creates drag effectively, which leads to the conclusion that it produces no thrust.