A fairing is a structure whose primary function is to produce a smooth outline and reduce drag.
These structures are generally light-weight shapes and covers for gaps and spaces between parts of an aircraft to reduce form drag and interference drag, and to improve appearance.
On aircraft, fairings are commonly found on:
- engine cowlings, to reduce parasitic drag by reducing the surface area, having a smooth surface and thus leading to laminar flow, and having a nose cone shape, which prevents early flow separation. The inlet and the nozzle in combination lead to an isotropic speed reduction around the cooling fins and due to the speed-squared law to a reduction in cooling drag.
- tail cones, to reduce the form drag of the fuselage, by recovering the pressure behind it. For the design speed they add no friction drag.
- wheels on fixed gear aircraft — often called "wheel pants". On the bad side they increase the frontal area and the surface, but on the good side they have a smooth surface, a pointy noise (a spherical nose cone is sub-optimal) for laminar flow, and a tail cone (see above).
- wing root, to reduce interference drag. On top and below the wing it consists of small rounded edge to reduce the surface and such friction drag. At the leading and trailing edge it consists of much larger taper and smoothes out the pressure differences: High pressure at the leading and trailing edge, low pressure on top of the wing and around the fuselage.
- wing tips, which may have a complex shape to reduce vortex generation and so also drag, especially at low speed
- fin and rudder tips, to reduce turbulence at the tip
- elevator and horizontal stabilizer tips
- strut-to-wing and strut-to-fuselage junctions
- fixed landing gear junctions
Flap track fairings
Most jet airliners
have a cruising speed between Mach 0.8 and 0.85. For aircraft operating in the transonic
regime (about Mach
0.8–1.2), wave drag
can be minimized by having a cross-sectional
area which changes smoothly along the length of the aircraft. This is known as the area rule
. On subsonic aircraft such as jet airliners, this can be achieved by the addition of smooth pods on the trailing edges of the wings. These pods are known as anti-shock bodies
, Küchemann Carrots, or flap track fairings, as they enclose the mechanisms for deploying the wing flaps