lander (space vehicle). A space vehicle designed to land on a celestial body, such as the moon or one of
the planets.

landing area (air traffic control). Any locality either on land, water, or structures, including
airports/heliports and intermediate landing fields, which is used, or intended to be used, for the landing and
takeoff of aircraft. Landing areas may or may not have facilities for the shelter and servicing of aircraft, or
for receiving or discharging passengers or cargo.

landing direction indicator. A device which visually indicates the direction in which landings and
takeoffs should be made. Wind cones, wind socks, and tetrahedrons are commonly used landing direction
indicators.

landing distance available (ICAO). The length of runway which is declared available and suitable for the
ground run of an aeroplane landing.

landing flaps (airplane secondary control surfaces). An airplane control surface used to increase the
camber, or curvature, of the wing airfoil. This increases both the lift and the drag produced by the wing.

By increasing the lift, the airplane can be landed at a slower airspeed, and by increasing the drag, the airplane can descend at a steeper angle without building up excessive airspeed. Some landing flaps increase the area of the wing as well as the camber. See plain flap, split flap, slotted flap, Fowler flap, and triple-slotted flap.
landing gear (aircraft component). The part of an aircraft structure that supports the aircraft when it is not flying. For operation from runways and dry ground, the landing gear uses wheels. Operation from snow and ice is done with skis, and operation from water is done with a landing gear using floats.
Wheeled landing gear is by far the most common, and there are two basic types: tricycle and tail wheel-type. The tail wheel-type landing gear is often called a conventional landing gear. In a tricycle landing gear, two main wheels are located behind the center of gravity, and a third wheel, nearly as large as the main wheels, is located near the nose of the aircraft. In a tail wheel-type landing gear, the two main wheels are ahead of the center of gravity, and a much smaller wheel is located at the tail of the aircraft.
Landing gear can be either fixed so it is always extended in the airstream or retractable. Retractable landing gear can be folded into the wing or fuselage when the aircraft is off the ground, reducing the drag caused by air flowing over the structure.