A leading edge is the front part of an airplane's wings that first makes contact with the airflow. In contrast to trailing edges, which host flaps, leading edges accommodate slats and other high-lift devices. These high-lift systems - typically a combination of leading-edge slats and multielement trailing-edge flaps - are vital for increasing lift at low speeds. Variable camber leading edges have been flight-tested, demonstrating adaptability in advanced aircraft designs.
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Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is the leading edge in aircraft?
The leading edge is the foremost edge of an aircraft's wing or airfoil, which first encounters the air as the aircraft moves forward. The frontmost edge of a wing or other airfoil of an aircraft sometimes contains slots or slats. The leading edge is the thick edge of the blade that meets the air.
The orientation of the leading edge varies. An unswept leading edge means it is perpendicular to the longitudinal axis of the aircraft. A wing with sweepback is struck by the same airflow at an angle smaller than 90 degrees. When a disturbance causes an aircraft with sweepback to slip, the low wing presents its leading edge at an angle more perpendicular to the relative airflow. Wing sweep is conventionally measured at the 25% chord line, and the chord generally varies along the wing.
The leading edge plays a part in the aerodynamics of flight. The boundary layer separates from the surface at the leading edge, and the radius of curvature on the upper wing surface is tight, causing flow separation. A hinged leading edge rotates first downward and then forward into a position where its forward edge seals against the lower surface of the fixed-wing leading edge.
What are leading edge devices in aviation?
Leading edge devices are movable or fixed surfaces attached to the wing's leading edge that increase camber, delay stalls, and let the wing produce the same lift at lower airspeed. By keeping airflow attached at higher angles of attack, they help airplanes fly safely and efficiently across a wide range of speeds, shorten takeoff and landing distance, and refine overall safety during low-speed operations like takeoff, initial climb, approach, and landing.
These devices can be split into four types: fixed slots, movable slats, leading edge flaps, and leading edge cuffs. Fixed slots are permanent openings built into the leading edge and they let high-pressure air from beneath the wing flow through the gap, energize the airflow over the top, and promote good low-speed handling qualities, but they carry a price in drag. Movable slats are extendable high-lift devices that slide forward on tracks, open a slot between the wing and the slat, increase both surface area and camber, and enable higher angles of attack. They are suited for airliners and high-performance aircraft. Leading edge flaps are hinged surfaces that deflect downward during takeoff and landing, increase camber for extra lift, and produce more lift at slower speeds, yet they are not as effective at delaying stall as slots or slats. Krueger flaps, the simplest leading edge device in use on high-performance airliners, extend panels forward from the lower surface of the wing and increase wing camber. They are used on the inboard wing of the Boeing 707.
Leading edge cuffs are fixed aerodynamic devices that modify airplane wings by permanently reshaping part of the leading edge down and forward. A leading edge cuff improves airflow at higher angles of attack, delays stall, and improves stall and spin characteristics. The cuff discontinuity generates a vortex that acts as a fence and prevents separated flow from progressing outboard. An inboard vortex and wing-tip vortex remove the boundary layer of the outer wing. Cuffs are factory-designed or aftermarket add-on modifications on general aviation aircraft, and they cause an aerodynamic penalty for cruise speed and reduce cruise efficiency.
What is the difference between leading edge and trailing edge in aviation?
The difference between leading edge and trailing edge is that the leading edge is the forward-most part of an aerodynamic surface like a wing; it is the first point that meets the airflow. The trailing edge is its rear counterpart where the airflow separated by the leading edge meets again. Distance from the leading to trailing edges is called the chord.
While the leading edge slices the oncoming air, the trailing edge hosts the flight control surfaces that direct the departing airflow. Lowering the trailing edge provides greater lift by increasing wing camber, and trailing edge flaps shorten takeoff and landing distance. During a tailslide, from an aerodynamic point of view, the trailing edge becomes the leading edge.
Both edges can be swept, and forward swept trailing edges are much more stable than backward swept trailing edges. Some jet fighters and most aerobatic airplanes adopted forward swept trailing edges in order to increase stability at high angle of attack.
