The trailing edge of an aerodynamic surface such as a
wing
A wing is a type of fin that produces both Lift (force), lift and drag while moving through air. Wings are defined by two shape characteristics, an airfoil section and a planform (aeronautics), planform. Wing efficiency is expressed as lift-to-d ...
is its rear edge, where the airflow separated by the
leading edge meets.
[Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 521. Aviation Supplies & Academics, 1997. ] Essential
flight control surfaces are attached here to control the direction of the departing air flow, and exert a controlling force on the aircraft. Such control surfaces include
ailerons on the wings for roll control,
elevators
An elevator (American English) or lift (English in the Commonwealth of Nations, Commonwealth English) is a machine that vertically transports people or freight between levels. They are typically powered by electric motors that drive tracti ...
on the
tailplane
A tailplane, also known as a horizontal stabilizer, is a small lift (force), lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters ...
controlling
pitch, and the
rudder
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium (usually air or water). On an airplane, the rudder is used primarily to counter adverse yaw ...
on the
fin controlling
yaw. Elevators and ailerons may be combined as
elevons on
tailless aircraft
In aeronautics, a tailless aircraft is a fixed-wing aircraft with no other horizontal aerodynamic surface besides its main wing. It may still have a fuselage, vertical tail fin (vertical stabilizer), and/or vertical rudder.
Theoretical advanta ...
.
The shape of the trailing edge is of prime importance in the aerodynamic function of any aerodynamic surface. A sharp trailing edge is always employed in an airfoil.
George Batchelor has written about:
:“ ... the remarkable controlling influence exerted by the sharp trailing edge of an aerofoil on the
circulation.”
[Batchelor, G. K. (1967), ''An Introduction to Fluid Dynamics'', p.438, Cambridge University Press.]
Extensions
Other sharp-edged surfaces that are attached to the trailing edges of wings or control surfaces include:
*On control surfaces:
:*
trim tabs
:*
servo tabs
:*
anti-servo tabs
*Other surfaces:
:*
flaps
Other equipment that may be attached to the trailing edges of wings include:
:*
anti-shock bodies
:*
static wicks
Trailing edge shape
The trailing edge is where the upper and lower surfaces of a wing meet. The angle between the upper and lower surfaces at the trailing edge is called the ''trailing edge angle''. If the trailing edge angle is zero it is described as a
cusped trailing edge.
In two-dimensional flow around a uniform wing of infinite span, the slope of the
lift curve is determined primarily by the ''trailing edge angle''. The slope is greatest if the angle is zero; and decreases as the angle increases. For a wing of finite span, the
aspect ratio
The aspect ratio of a geometry, geometric shape is the ratio of its sizes in different dimensions. For example, the aspect ratio of a rectangle is the ratio of its longer side to its shorter side—the ratio of width to height, when the rectangl ...
of the wing also significantly influences the slope of the curve. As aspect ratio decreases, the slope also decreases.
[Abbott, I.H., and Von Doenhoff, A.E. (1949) ''Theory of Wing Sections'', section 1.3]
References
{{Aircraft components
Aircraft aerodynamics
Aircraft wing design