PROPELLER OPERATION

BASIC FACTS
The propeller blade is an airfoil which propels the airplane through the air by converting the rotating power of the engine into thrust. Blades are twisted to optimize the performance of the propeller based on variable operating conditions. Wooden props were used almost exclusively on personal and business aircraft prior to World War II. During the 1940s, solid steel propellers were made for military use. Modern propellers are fabricated from high-strength, heat-treated, aluminum alloy forgings. New composite materials are being used in applications where weight and mass are critical.

Propellers are typically designed with two to six blades. Generally, props with more than three blades are used primarily for twin-engine aircraft. These blades tend to be shorter for increased ground clearance and more fuselage clearance. Multi-blade props also produce higher, less objectionable sound frequency; reduced vibration; greater flywheel effect and improved aircraft performance.

McCauley propellers are identified by a model designation and a serial number. On one-piece, fixed-pitch props, the serial number is stamped on the camber side of the hub face. Variable pitch propellers have separate numbers for the hub (stamped on the side) and for each detachable blade (stamped on the butt end of the blade inside the hub).

Types of Propellers Manufactured by McCauley

Propellers are classified according to pitch configuration. Blade pitch is the angle of the blades with relation to the plane of rotation and is a significant variable affecting the performance of the propeller.

Fixed Pitch: a one-piece prop with a single fixed blade angle. The pitch (blade angle) must be high enough to offer good cruising performance yet low enough to achieve acceptable takeoff and climb characteristics.

Constant Speed: a prop used with a governor, that automatically provides constant RPM by controlling the forces acting on the propeller to change the blade angle within a preset range.

Full-Feathering: a prop which allows blades to be rotated to a high positive angle to stop rotation (windmilling) after an engine is shut down, thereby reducing drag and asymmetric control forces on twin-engine applications.

Reversing: a prop with blades that can be rotated to a position less than the normal positive low blade angle setting until a negative blade angle is obtained, producing a rearward thrust to slow down, stop or move the aircraft backward. Typically provided for turbine installations.

Beta Control: a prop which allows the manual repositioning of the propeller blade angle beyond the normal low pitch stop. Used most often in taxiing, where thrust is manually controlled by adjusting blade angle with the power lever. These types of McCauley propellers are installed exclusively on turbine engines.

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