Meteorological conditions expressed in terms of visibility,  distance from clouds, and ceiling less than the minimums  specified for visual meteorological conditions. Flight without  visual reference to the horizon. Interference drag.  Type of drag produced by placing two  objects adjacent to one another. Combines the effects of form  drag and skin friction. International Civil Aviation Organization (ICAO).  The  United Nations agency for developing the principles and  techniques of international air navigation, and fostering  planning and development of international civil air  transport. International standard atmosphere (IAS).  A model of  standard variation of pressure and temperature.  Inversion.  An increase in temperature with altitude. Isobars.  Lines which connect points of equal barometric  pressure. Jet stream.  A high-velocity narrow stream of winds, usually  found near the upper limit of the troposphere, which flows  generally from west to east. Keel.  See wing keel and carriage keel. Judgment.  The mental process of recognizing and analyzing  all pertinent information in a particular situation, a rational  evaluation of alternative actions in response to it, and a timely  decision on which action to take. KIAS.  Knots indicated airspeed.  Kinesthesia.  The sensing of movements by feel. King post.  The post on top of the wing which is attached to  the keel that holds used for the ground wires which hold up  the wings on the ground and during negative loads during  flight.  Knowledge exam.  See FAA Knowledge Exam. Lateral axis.  An imaginary line passing through the center  of gravity of a WSC and extending across the WSC from one  side of the aircraft to the other side. Leading edge.  The part of an airfoil that meets the airflow  first. This as a structural tube on the WSC airfoil. Lift.  One of the four main forces acting on an aircraft. On a  WSC, an upward force created by the effect of airflow as it  passes over and under the wing. Lift coefficient.  A coefficient representing the lift of a given  airfoil. Lift coefficient is obtained by dividing the lift by the  free-stream dynamic pressure and the representative area  under consideration. Lift/drag ratio.  The efficiency of an airfoil section. It is the  ratio of the coefficient of lift to the coefficient of drag for  any given angle of attack. Lift-off.  The act of becoming airborne as a result of the wings  lifting the airplane off the ground, or the pilot rotating the  nose up, increasing the angle of attack to start a climb. Light-Sport Aircraft (LSA).  An aircraft that meets the  requirements defined in 14 CFR section 1.1, regardless of  airworthiness certification. Limit load factor.  Amount of stress, or load factor, that an  aircraft can withstand before structural damage or failure  occurs. Load factor.  The ratio of a specified load to the total weight  of the aircraft. The specified load is expressed in terms of  any of the following: aerodynamic forces, inertial forces, or  ground or water reactions. Also referred to as G-loading. Logbook.  A record of activities: flight, instruction, inspection  and maintenance. Reference 14 CFR part 43, 14 CFR section  61.51, and 14 CFR section 91.417. Longitude.  Measurement east or west of the Prime Meridian  in degrees, minutes, and seconds. The Prime Meridian is 0°  longitude and runs through Greenwich, England. Lines of  longitude are also referred to as meridians. Longitudinal axis.  An imaginary line through an aircraft  from nose to tail, passing through its center of gravity about  which the aircraft rolls in flight. The longitudinal axis is also  called the roll axis of the aircraft. Longitudinal stability (pitching).  Stability about the lateral  axis. A desirable characteristic of an airplane whereby it tends  to return to its trimmed angle of attack after displacement. LSA.  See Light-Sport Aircraft. MAC.  See mean aerodynamic chord.  G-10