| A | B |
|---|
| Absolute Altitude | The actual distance an object is above the ground |
| Advancing Blade | The blade moving in the same direction as the helicopter |
| Airfloil | Any surface designed to obtain a useful reaction of lift, or negative lift, as it moves through the air |
| Agonic Line | Aline along which there is no magnetic variation |
| Air Density | The density of the air in terms of mass per unit volume |
| Airworthiness directive | when an unsafe condition exists with an aircraft, the FAA issues an air worthiness directive to notify concerned parties of the condition and to describe the appropriate corrective action |
| Altimeter | An instrument that indicates flight altitude by sensing pressure changes |
| Angle of Attack | The angle between the airfoil's chord line and the relative wind |
| Articulated Rotor | A rotor system in which each of the blades is connected to the rotor hub in such a way that it is free to change its pitch angle, and move up and down and fore and aft in its plane of rotation |
| Autorotation | The condition of flight during which the main rotor is driven only by aerodynamic forces with no power from the engine |
| Axis-of-rotation | imaginary line about which the rotor rotates. Represented by a l line drawn through the center of, and perpendicular to, the tip-path plane. |
| Basic Empty Weight | The weight of the standard rotorcraft, operational equipment, unusable fuel, and full operation fluids, including full engine oil. |
| Blade Coning | An upward sweep of rotor blades as a result of lift and centrifugal force |
| Blade Damper | A device attached to the drag hinge to restrain the fore and aft movement of the rotor blade |
| Blade Feathering | The rotation of the blade around the spanwise (pitch change) axis |
| Blade Flap | The ability of the rotor blade to move in a vertical direction. |
| Blade Grip | The part of the hub assembly to which the rotor blades are attached, sometimes referred to as blade forks. |
| Blade Lead or Lag | The fore and aft movement of the blade in the plane of rotation. |
| Blade Loading | The load imposed on rotor blades, determinded by dividing the total weight of the helicopter by the combined area of all the rotor blades |
| Blade Root | The part of the blade that attaches to the blade grip |
| Blade Span | The length of a blade from its tip to its root |
| Blade Stall | The condition of the rotor blade when it is operating at an angle of attack greater than the maximum angle of lift |
| Blade Tip | The further most part of the blade from the hub of the rotor |
| Blade Track | The relationship of the blade tips in the plane of rotation. |
| Blade Tracking | The mechanical procedure used to bring the blades of the rotor into a satisfactory relationship with each other under dynamic conditions so that all blades rotate on a common plane |
| Blade Twist | The variation in the angle of incidence of a blade between the root and the tip |
| Blowback | The tendency of the rotor disc to tilt aft in the forward flight as a result of flapping |
| Calibrated Airspeed (CAS) | Indicated airspeed of an aircraft, corrected for installation and instrumentation errors. |
| Center of Pressure | The point where the resultant of all the aerodynamic forces acting on an airfoil intersects the chord |
| Chip Detector | A warning device that alerts you to any abnormal wear in a transmission or engine |
| Chord | An imaginary straight line between the leading and trailing edges of an airfoil section |
| Chordwise Axis | A term used in reference to semirigid rotors describing the flapping or teetering axis of the rotor |
