GT Glossary

GT GLOSSARY

Accumulator	A device to ald in unfeathering a propeller.
Aerodynamic twisting moment	An operational force on a propeller which tends to increase the propeller blade angle.
Angle of attack	The angle between the chord line of a propeller blade section and the relative wind.
Anti-icing system	A system which prevents the formation of ice on propeller blades.
Automatic-propeller	A propeller which changes blade angles in response to operational forces and is not controlled from the cockpit. Trade name: Aeromatic.
Back	The curved side of a propeller airfoil section that can be seen while standing in front of the airplane.
Blade	One arm of a propeller from the hub to the tip.
Blade angle	The angle between the blade section chord line and the plane of rotation of the propeller.
Blade index number	The maximum blade angle on a Hamilton-Standard counterweight propeller.
Blade paddle	A tool used to turn the blades in the hub.
Blade root	The portion of a blade which is nearest the hub.
Blade station	A distance from the center of the propeller hub measured in inches.
Boots	Ice elimination components which are attached to the leading edge of propeller blades.
Boss	The center portion of a fixed-pitch propeller.
Brush block	The component of a de-icing and/or reversing system which is mounted on the engine nose case and holds the brushes which transfer electrical power to the slip ring.
Centrifugal force	The force on a propeller which tends to throw the blades out from the propeller center.
Centrifugal twisting moment	The force on a propeller which tends to dcrease the propeller blade angle.
Chord line	The imaginary line which extends from the leading edge to the trailing edge of a blade airfoil section.
Comparison unit	The unit in a synchronization or synchrophasing system which compares the signals of the master engine and the slave engine and sends a signal to correct the slave engine RPM or blade phase angle.
Cone	The component used in a splined-shaft in-stallation which centers the propeller on the crankshaft.
Constant-speed system	A sysyem which uses a governor to adjust the propeller blade angle to maintain a selected RPM.
Controllale-pitch propeller	A propeller whose pitch can be changed in flight by the pilot’s control lever or switch.
Critical range	The RPM range at which destructive harmonic vibrations exist.
De-icing system	An ice elimination system which allows ice to form and then breaks it loose in cycles.
Dome assembly	The pitch-changing mechanism of a Hydromatic propeller.
Effective pitch	The distance forward that an aircraft actually moves in one revolution of th epropeller.
Face	The flat or thrust side of a propeller blade.
Feather	The rotation of the propeller blades to an angle of about 90 degrees which will eliminate the drag of a windmilling propeller.
Fixed-pitch propeller	A propeller, used on light aircraft, whose blade angles cannot be changed.
Flanged shaft	A crankshaft whose propeller mounting surface forms a flat plate 90 degrees to the shaft centreline.
Frequency generator	The engine RPM signal generator for some synchronization systems.
Geometric pitch	The theoretical distance that an aircraft will move forward in one revolution of the propeller.
Governor	The propeller control device in a constant-speed system.
Go no-go gauge	A gauge used to measure wear between the splines of a splined crankshaft.
Ground-adjustable propellers	A propeller which can be adjusted on the ground to change the blade angles.
Hub	The central portion of a propeller which is fitted to the engine crankshaft and carries the blades.
Hydromatic	A trade name for one type of Hmilton-Standar hydraulically operated propellers.
Integral oil control assembly	A self-contained propeller control unit used on some transport aircraft.
Leading edge	The forward edge of a propeller blade.
Overhaul facility	An FAA approved facility for major overhauls and repairs.
Pitch	The same as geometric pitch. Often used interchangeably with blade angle.
Pitch distribution	The twist in a propeller blade along its length.
Pitch lock	A mechanism used on some transports to prevent excessive overspeeding of the propeller if the governor fails.
Plane of rotation	The plane in which the propeller rotates, 90 degrees to the crankshaft centreline.
Propellers	A device for converting engine horse-power into usable thrust.
Propeller repair station	See overhaul facility.
Propeller track	The arc described by a propeller blade as the propeller rotates.
Pulse generator	The unit which generates an RPM and blade position signal in a synchrophasing system.
Radial clearance	The distance from the edge of the propeller disc to an object near the edge of the disc, perpendicular to the crankshaft centreline.
Reversing	Rotation of the propeller blades to a negative angle to produce a braking or reversing thrust.
Safetying	The installation of a safety device such as safety wire or a cotter pin.
Selector valve	Propeller control unit in a two-position propeller system.
Shank	The thickened portion of the blade near the center of the propeller.
Shoe	See boot.
Shoulder	The flanged area on the butt of a propeller blade which is used to retain the propeller blades in the hub.
Slinger ring	The fluid distribution unit on the rear of a propeller hub using an anti-icing system.
Slip	The difference between geometric pitch and effective pitch.
Snap ring	A component of a splined or tapered shaft installation which is used to ald in removal of the propeller.
Spider	The central component on many controllable-pitch propellers which mounts on the crankshaft and has arms on which the blades are installed.
Splined shaft	A cylindrical-shaped crankshaft extension which has splines on its surface to prevent propeller rotation on the shaft.
Static RPM	The maximum RPM that can be obtained at full throttle on the ground in a no-wind condition.
Synchronization system	A system which keeps all engines at the same RPM.
Synchrophasing system	A refined synchronization system which allows the pilot to adjust the blade relative position as they rotate.
Tachometer-generator	The RPM-sensing unit of some synchronization systems.
Tapered shaft	A crankshaft design whose propeller-mounting surface tapers to a smaller diameter and acts like a cone seating surface.
Thrust bending force	An operational force which tends to bend the propeller blades forward.
Tip	The portion of the blade farthest from the hub.
Torque bending force	An operational force which tends to bend the propeller blades in the direction opposite to the direction of rotation.
Two-position propeller	A propeller which can be changed between two blade angles in flight.