Which FAR part contains information about the airworthiness of propellers?

The correct choice pertains to Federal Aviation Regulations (FAR) Part 35, which specifically addresses the airworthiness standards for propellers. This regulation outlines the design, performance, and operating criteria that must be met to ensure that aircraft propellers are safe and reliable for flight.

FAR Part 35 includes detailed requirements for vibration testing, materials, structural integrity, and maintenance to maintain airworthiness. These standards are critical for ensuring that propellers operate effectively and do not pose safety risks during flight operations.

The other options either pertain to different aspects of aviation safety or aircraft components. Part 23 deals with airworthiness standards for normal category airplanes, Part 33 covers the airworthiness standards for aircraft engines, and Part 36 focuses on noise standards for various categories of aircraft. Thus, Part 35 is the specific regulation that directly addresses the standards necessary for propeller airworthiness.