Which of the following is NOT a specified propeller diameter for the Cessna 152?

The specified propeller diameters for the Cessna 152 are critical for maintaining the aircraft's performance and ensuring safe operation. In this context, the diameter of the propeller impacts aspects such as thrust, engine RPM, and overall efficiency.

The Cessna 152 typically uses propellers with diameters of 67.5 inches, 68 inches, and 69 inches, all of which are standard specifications for this aircraft model. These sizes are derived from the design requirements that optimize the performance characteristics of the aircraft.

In contrast, the 66 inches diameter is not used for the Cessna 152. This option does not align with the manufacturers’ specifications for this model, making it the incorrect choice. Understanding these dimensions is essential for pilots to select the appropriate propeller and ensure the aircraft's performance standards are met.