22.24 Propellers

22.24.2 Define blade face, blade angle, pitch (or helix) angle, helical twist, angle of attack.

Blade face

Blade angle;

In propeller terminology, the blade angle refers to the angle between the chord line of a propeller blade and the plane of rotation. The chord line is an imaginary line that connects the leading edge to the trailing edge of the blade. The blade angle can be adjusted to optimize the performance of the propeller for different flight conditions. Some common types of blade angles include: 1. Fixed pitch: A fixed pitch propeller has a constant blade angle that cannot be adjusted in flight. This type of propeller is simple and reliable, but may not be as efficient as other types of propellers. 2. Ground adjustable: A ground adjustable propeller has a blade angle that can be adjusted on the ground to optimize performance for different flight conditions. This type of propeller is often used in experimental or homebuilt aircraft. 3. Constant speed: A constant speed propeller has a mechanism that automatically adjusts the blade angle to maintain a constant engine speed. This type of propeller is often used in general aviation and commercial aircraft. 4. Variable pitch: A variable pitch propeller allows the pilot to manually adjust the blade angle in flight to optimize performance for different flight conditions. This type of propeller is often used in high-performance or racing aircraft. Overall, the blade angle is an important factor in determining the performance and efficiency of a propeller. Different blade angles can produce different amounts of thrust, speed, and efficiency, depending on the design and intended use of the propeller.