Common Terms

Blade: one arm of a propeller from hub to tip.

Hub: center section of the propeller which carries the blades and is attached to the engine shaft.

Spinner: a metal cover enclosing the propeller hub, which improves the appearance of the propeller and may also streamline airflow for engine cooling purposes.

Blade tip: the part of the blade furthest from the hub.

Blade root: the section of the blade nearest the hub.

Blade shank: the portion of a blade inside the hub used to retain the blade.

Blade camber surface: the cambered or most-cambered side of a blade (visible from front of the aircraft).

Blade face or thrust surface: the flat side of a blade (normally visible from the cockpit of the aircraft).

Blade leading edge: the forward full ³cutting² edge of the blade that leads in the direction of rotation.

Blade trailing edge: the continuous edge of the blade that trails the leading edge in the direction of rotation.

Governor: a device, generally mounted on and driven by the engine, which senses and controls engine speed (RPM) by hydraulically adjusting the blade angle of the propeller.

Prop diameter: the diameter of the circle circumscribed by the blade tips.

Blade station: one of the designated distances along the blade as measured from the center of the hub.

Blade thickness: the maximum thickness between the cambered surface and the face or thrust surface at a given blade station.

Blade width: the measurement between the leading edge and the trailing edge at a given station.

Chord line: a theoretical straight line (perpendicular to blade length) drawn between the leading and trailing edges of the blade.

Blade angle: the angle between the chord line of a propeller blade section and a plane perpendicular to the axis of propeller rotation.

Blade angle settings: low and high angle settings of a controllable-pitch prop ­ for feather, reverse, latch and start locks ­ which are determined by built-in mechanical hard stops.