HUNTING—Movement of a blade with respect to the other blades in the plane of rotation, sometimes called leading or lagging.
INERTIA—The property of matter by which it will remain at rest or in a state of uniform motion in the same direction unless acted upon by some external force.
IN GROUND EFFECT (IGE) HOVER—Hovering close to the surface (usually less than one rotor diameter distance above the surface) under the influence of ground effect.
INDUCED DRAG—That part of the total drag that is created by the production of lift.
INDUCED FLOW—The component of air flowing vertically through the rotor system resulting from the production of lift.
ISOGONIC LINES—Lines on charts that connect points of equal magnetic variation.
KNOT—A unit of speed equal to one nautical mile per hour.
L/DMAX—The maximum ratio between total lift (L) and total drag (D). This point provides the best glide speed. Any deviation from the best glide speed increases drag and reduces the distance you can glide.
LATERIAL VIBRATION—A vibration in which the movement is in a lateral direction, such as imbalance of the main rotor.