A
fairing is a structure whose primary function is to produce a smooth outline and reduce
dragIn fluid dynamics, drag refers to forces that oppose the relative motion of an object through a fluid . Drag forces act in a direction opposite to the oncoming flow velocity...
.
These structures are generally light-weight shapes and covers for gaps and spaces between parts of an
aircraftAn aircraft is a vehicle which is able to fly by being supported by the air, or in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil An aircraft is a vehicle which is able to fly by being supported...
to reduce form drag and interference drag, and to improve appearance.
On aircraft, fairings are commonly found on:
- engine cowling
A cowling is the covering of a vehicle's engine, most often found on automobiles and aircraft.A cowling may be used:* for drag reduction* for engine cooling by directing airflow* as an air intake for jet engines* for decorative purposes...
s, to reduce parasitic dragParasitic drag is drag caused by moving a solid object through a fluid medium . Parasitic drag is made up of many components, the most prominent being form 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 separationAll solid objects travelling through a fluid acquire a boundary layer of fluid around them where viscous forces occur in the layer of fluid close to the solid surface. Boundary layers can be either laminar or turbulent...
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Discussion
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A
fairing is a structure whose primary function is to produce a smooth outline and reduce
dragIn fluid dynamics, drag refers to forces that oppose the relative motion of an object through a fluid . Drag forces act in a direction opposite to the oncoming flow velocity...
.
These structures are generally light-weight shapes and covers for gaps and spaces between parts of an
aircraftAn aircraft is a vehicle which is able to fly by being supported by the air, or in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil An aircraft is a vehicle which is able to fly by being supported...
to reduce form drag and interference drag, and to improve appearance.
Types
On aircraft, fairings are commonly found on:
- engine cowling
A cowling is the covering of a vehicle's engine, most often found on automobiles and aircraft.A cowling may be used:* for drag reduction* for engine cooling by directing airflow* as an air intake for jet engines* for decorative purposes...
s, to reduce parasitic dragParasitic drag is drag caused by moving a solid object through a fluid medium . Parasitic drag is made up of many components, the most prominent being form 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 separationAll solid objects travelling through a fluid acquire a boundary layer of fluid around them where viscous forces occur in the layer of fluid close to the solid surface. Boundary layers can be either laminar or turbulent...
. The inletAn inlet is a narrow body of water between islands or leading inland from a larger body of water, often leading to an enclosed body of water, such as a sound, bay, lagoon or marsh. In sea coasts an inlet usually refers to the actual connection between a bay and the ocean and is often called an...
and the nozzleA nozzle is a mechanical device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice....
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", "speed fairings" or in the UK
The United Kingdom of Great Britain and Northern Ireland is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of Ireland, and many small islands...
, "wheel spatsA spat is a type of shoe accessory covering the instep and ankle. Spats were primarily worn in the late 19th and early 20th centuries.- Spats as items of uniform :...
". These fairings are a trade-off in advantages, as they increase the frontal and surface area, but also provide a smooth surface, a faired nose and tail for laminar flow, in an attempt to reduce the turbulence created by the round wheel and its associated gear legs and brakes.
- wing root
The wing root is that part of the wing, on a fixed-wing aircraft, that is closest to the fuselage. On simple designs where the wing joins the fuselage in a high wing, mid-wing or low wing monoplane configuration this is usually easy to identify...
, 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 smooths 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
A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft,or other conveyance that moves through a fluid . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...
, to reduce turbulence at the tip
- elevator and horizontal stabilizer tips
Elevators are control surfaces, usually at the rear of an aircraft, which control the aircraft's orientation by changing the pitch of the aircraft, and so also the angle of attack of the wing. In simplified terms, they make the aircraft nose-up or nose-down...
- strut-to-wing and strut-to-fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
junctions
- fixed landing gear
Landing Gear is Devin the Dude's fifth studio album. It was released on October 7 2008. It will be his first studio album since signing with the label Razor & Tie. It features a high-profile guest appearance from Snoop Dogg. As of October 30, 2008, the album has sold 18,906 copies.-Track...
junctions
Flap track fairings
Most
jet airlinerA jet airliner is an airliner that is powered by jet engines. This term is sometimes contracted to jetliner.In contrast to today's relatively fuel-efficient, turbofan-powered air travel, first generation jet airliner travel was noisy and fuel inefficient...
s have a cruising speed between Mach 0.8 and 0.85. For aircraft operating in the
transonicTransonic is an aeronautics term referring to the condition in which a range of velocities of airflow exist surrounding and flowing past an air vehicle or an airfoil. Air flow velocities are concurrently below, at, and above the speed of sound at the pressure and temperature of the airflow of the...
regime (about
MachMach number is the speed of an object moving through air, or any fluid substance, divided by the speed of sound as it is in that substance...
0.8–1.2),
wave dragWave drag is an aerodynamics term that refers to a sudden and very powerful form of drag that appears on aircraft and blade tips moving at high-subsonic and supersonic speeds.- Overview :...
can be minimized by having a
cross-sectionalIn geometry, a cross-section is the intersection of a body in 2-dimensional space with a line, or of a body in 3-dimensional space with a plane, etc. More plainly, when cutting an object into slices one gets many parallel cross-sections....
area which changes smoothly along the length of the aircraft. This is known as the
area ruleThe Whitcomb area rule, also called the transonic area rule, is a design technique used to reduce an aircraft's drag at transonic and supersonic speeds, particularly between Mach 0.8 and 1.2...
. 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 bodiesAnti-shock bodies are pods placed at the trailing edge of the wings of some transonic aircraft wings in order to reduce wave drag as the aircraft enters the transonic regime . Most jet airliners have a cruising speed between Mach 0.8 and 0.85...
, Küchemann Carrots, or flap track fairings, as they enclose the mechanisms for deploying the wing
flapsFlaps are hinged surfaces on the trailing edge of the wings of a fixed-wing aircraft. As flaps are extended, the stalling speed of the aircraft is reduced, which means that the aircraft can fly safely at slower speeds...
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