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blade and the lift produced by the blades.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 77
blade cuff (propeller blade component). A metal, wood, or plastic cuff installed around the shank of a
propeller blade to carry the airfoil shape of the blade all the way to the propeller hub.
The airfoil shape of the cuff pulls cooling air into the engine.
blade damper (helicopter rotor blade component). A shock absorbing mechanism installed between a
helicopter rotor blade and the hub to dampen lead- and lag-vibrations of the blade.
blade droop (helicopter rotor). The angle formed between the spanwise axis of the rotor blades, when the
blades are not rotating, and the plane of rotation of the blades perpendicular to the rotor shaft.
The only force acting on the blade to cause droop is gravity.
blade face (propeller blade). The flat surface of a propeller blade. The face of a propeller blade compares
with the flat bottom portion of a wing airfoil section. See illustration for blade back.
blade flapping (helicopter rotor blades). Movement of a helicopter rotor blade in which the blades rise
and descend as they rotate.
Blade flapping compensates for asymmetrical lift. The advancing blade flaps up, decreasing its
angle of attack and the amount of lift it produces. At the same time, the retreating blade flaps downward,
increasing its angle of attack and the amount of lift it produces.
blade grips (helicopter rotor blade component). The portion of a helicopter rotor hub into which the
blades fit. Blade grips are sometimes called blade forks. The rotor blade is attached to the blade grip with a
lead-lag hinge pin.
blade loading (helicopter rotor blades). The amount of weight each square foot of a helicopter rotor blade
supports. Blade loading is found by dividing the total weight of the helicopter by the area of the rotor
blades.
Blade loading is not to be confused with disk loading, which is the total weight of the helicopter
divided by the area of the disk swept by the rotor blades.
blade root (propeller blade). The portion of a propeller blade that fits into the hub. The blade root is also
called the blade butt.
blade section (propeller blade). A cross section of a propeller blade perpendicular to the span of the blade.
blade shank (propeller blade). The thick, rounded portion of a propeller blade near the hub.
blade span (helicopter rotor blade). The length of a helicopter rotor blade from its tip to its root.
blade stall (helicopter rotor flight condition). A condition of flight of a helicopter when the retreating
blade is operating at an angle of attack higher than will allow the air to flow over its upper surface without
turbulence.
Blade stall occurs when the helicopter is in high-speed forward flight or when it is settling with
power.
blade station (propeller blade). The distance, measured in inches, between the center line of the propeller
shaft and a location along the blade of a propeller.
Blade station measurements are used to identify locations along the blade of a propeller.
blade sweeping (helicopter rotor). The adjustment of chordwise balance of a helicopter rotor by moving
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 78
the tip of one of the blades backward or forward in its plane of rotation by changing the length of the drag
brace.
blade tabs (helicopter rotor component). Fixed tabs mounted on the trailing edge of a helicopter rotor
blade. Blade tabs are adjusted to cause the rotor blades to track properly.
blade tip (propeller blade). The part of a propeller blade the greatest distance from the hub.
blade track (helicopter rotor). The condition of a helicopter rotor in which each blade follows in exactly
the same path as the blade ahead of it.
blade tracking (helicopter rotor). The maintenance procedure in which the blades of a helicopter rotor are
adjusted so the tip of each blade follows the same path as the tip of the blade ahead of it.
Blade tracking minimizes vibration by causing the blades to travel in the same plane.
blade twist (helicopter rotor). The progressive change in the angle of incidence of a helicopter rotor blade
from root to tip. Blade twist is normally built into the blade when it is manufactured, but some degree of
twist can also be caused by aerodynamic forces.
blade twist (propeller blade). The decrease in the pitch angle of a propeller blade as the distance from the
hub increases.
The amount of thrust produced by a propeller blade is determined by the pitch angle of the blade
and the speed at which the blade is moving through the air. The speed of the blade increases as the distance
from the hub increases, so, to maintain a constant thrust along the blade, the blade angle must be decreased
　
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