blade antenna (radio antenna). A wide-band, quarter-wavelength antenna used on aircraft for communications or navigation in the UHF or VHF bands.
blade area (helicopter rotor). The total area of all of the rotor blades of a helicopter. Blade area is a constant for each helicopter.
blade back (propeller blade). The curved portion of a propeller blade. The back of a propeller blade is the same part of the airfoil as the upper surface of an aircraft wing.

blade beam (propeller tool). See blade wrench.
blade butt (propeller blade). The root end of a propeller blade. The blade butt fits into the hub of the propeller.
blade chord (propeller blade). A straight line through a propeller blade between its leading edge and its trailing edge.
blade coning angle (helicopter rotor blade). The angle formed between the spanwise axis of a helicopter rotor blade, when the rotor system is producing lift, and a plane at right angles to the rotor mast.
The coning angle is caused by the relationship between the centrifugal force acting on the rotor blade and the lift produced by the blades.
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.