![Light aircraft aileron and trim tab](https://upload.wikimedia.org/wikipedia/commons/2/21/Light_aircraft_aileron_and_trim_tab.JPG)
An aileron (French for "little wing" or "fin") is a hinged
flight control surface
Aircraft flight control surfaces are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude.
Development of an effective set of flight control surfaces was a critical advance in the development of aircraft. Ea ...
usually forming part of the
trailing edge
The trailing edge of an aerodynamic surface such as a wing 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. ...
of each
wing
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expres ...
of a
fixed-wing aircraft
A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane, which is capable of flight using wings that generate lift caused by the aircraft's forward airspeed and the shape of the wings. Fixed-wing aircraft are distinc ...
. Ailerons are used in pairs to control the aircraft in
roll
Roll or Rolls may refer to:
Movement about the longitudinal axis
* Roll angle (or roll rotation), one of the 3 angular degrees of freedom of any stiff body (for example a vehicle), describing motion about the longitudinal axis
** Roll (aviation), ...
(or movement around the aircraft's
longitudinal axis), which normally results in a change in flight path due to the tilting of the
lift vector
A fluid flowing around an object exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the force parallel to the flow directi ...
. Movement around this axis is called 'rolling' or 'banking'.
Considerable controversy exists over credit for the invention of the aileron. The
Wright brothers and
Glenn Curtiss
Glenn Hammond Curtiss (May 21, 1878 – July 23, 1930) was an American aviation and motorcycling pioneer, and a founder of the U.S. aircraft industry. He began his career as a bicycle racer and builder before moving on to motorcycles. As early ...
fought a years-long
legal battle
-
A lawsuit is a proceeding by a party or parties against another in the civil court of law. The archaic term "suit in law" is found in only a small number of laws still in effect today. The term "lawsuit" is used in reference to a civil acti ...
over the Wright patent of 1906, which described a method of wing-warping to achieve lateral control. The brothers prevailed in several court decisions which found that Curtiss's use of ailerons violated the Wright patent. Ultimately, the
First World War
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
compelled the U.S. Government to legislate a legal resolution. A much earlier aileron concept was patented in 1868 by British scientist
Matthew Piers Watt Boulton
Matthew Piers Watt Boulton (22 September 1820 – 30 June 1894), also published under the pseudonym M. P. W. Bolton, was a British classicist, elected member of the UK's Metaphysical Society, an amateur scientist and an inventor, bes ...
, based on his 1864 paper ''On Aërial Locomotion''.
History
![Aerial Locomotion coverpage, 1864](https://upload.wikimedia.org/wikipedia/commons/3/30/Aerial_Locomotion_coverpage%2C_1864.jpg)
The name "aileron", from French, meaning "little wing", also refers to
the extremities of a bird's wings used to control their flight.
It first appeared in print in the 7th edition of Cassell's French-English Dictionary of 1877, with its lead meaning of "small wing". In the context of powered airplanes it appears in print about 1908. Prior to that, ailerons were often referred to as
rudders
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally air or water). On an aircraft the rudder is used primarily to counter adverse ya ...
, their older technical sibling, with no distinction between their orientations and functions, or more descriptively as ''horizontal rudders'' (in French, ''gouvernails horizontaux''). Among the earliest printed aeronautical use of 'aileron' was that in the French aviation journal ''
L'Aérophile
''L’Aérophile'' ("The Aerophile") was a French aviation magazine published from 1893 to 1947. It has been described as "the leading aeronautical journal of the world" around 1910.
History and contents
''L’Aérophile'' was founded and r ...
'' of 1908.
Ailerons had more or less completely supplanted other forms of lateral control, such as
wing warping
Wing warping was an early system for lateral (roll) control of a fixed-wing aircraft. The technique, used and patented by the Wright brothers, consisted of a system of pulleys and cables to twist the trailing edges of the wings in opposite direc ...
, by about 1915, well after the function of the rudder and
elevator
An elevator or lift is a wire rope, cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or deck (building), decks of a building, watercraft, ...
flight controls had been largely standardised. Although there were previously many conflicting claims over who first invented the aileron and its function, i.e., lateral or roll control,
the flight control device was invented and described by the British scientist and metaphysicist
Matthew Piers Watt Boulton
Matthew Piers Watt Boulton (22 September 1820 – 30 June 1894), also published under the pseudonym M. P. W. Bolton, was a British classicist, elected member of the UK's Metaphysical Society, an amateur scientist and an inventor, bes ...
in his 1864 paper ''On Aërial Locomotion''. He was the first to patent an aileron control system in 1868.
Boulton's description of his lateral flight control system was "the first record we have of appreciation of the necessity for active lateral control as distinguished from
assive lateral stability... With this invention of Boulton's we have the birth of the present-day three torque method of airborne control" as was praised by
Charles Manly
Charles Manly (May 13, 1795May 1, 1871) was a lawyer who served as the 31st governor of the U.S. state of North Carolina from 1849 to 1851. He was the last member of the Whig Party to hold the office. After one two-year term, Manly was defea ...
.
This was also endorsed by C.H. Gibbs-Smith.
Boulton's British patent, No. 392 of 1868, issued about 35 years before ailerons were "reinvented" in France, became forgotten and lost from sight until after the flight control device was in general use.
Gibbs-Smith stated on several occasions that if the Boulton patent had been revealed at the time of the
Wright brothers' legal filings, they might not have been able to claim priority of invention for the lateral control of flying machines. The fact that the Wright brothers were able to gain a patent in 1906 did not invalidate Boulton's lost and forgotten invention.
Ailerons were not used on manned aircraft until they were employed on
Robert Esnault-Pelterie Robert Albert Charles Esnault-Pelterie (8 November 1881 – 6 December 1957) was a French aircraft designer and spaceflight theorist. He is referred to as being one of the founders of modern rocketry and astronautics, along with the Russian Kons ...
's glider in 1904,
although in 1871 a French military engineer,
Charles Renard, built and flew an unmanned glider incorporating ailerons on each side (which he termed 'winglets'), activated by a Boulton-style pendulum controlled single-axis autopilot device.
[Bullmer 2009, p. 20.]
The pioneering U.S. aeronautical engineer
Octave Chanute
Octave Chanute (February 18, 1832 – November 23, 1910) was a French-American civil engineer and aviation pioneer. He provided many budding enthusiasts, including the Wright brothers, with help and advice, and helped to publicize their flying ...
published descriptions and drawings of the
Wright brothers'
1902 glider
The Wright brothers designed, built and flew a series of three manned gliders in 1900–1902 as they worked towards achieving powered flight. They also made preliminary tests with a kite in 1899. In 1911 Orville conducted tests with a much mor ...
in the leading aviation periodical of the day, ''
L'Aérophile
''L’Aérophile'' ("The Aerophile") was a French aviation magazine published from 1893 to 1947. It has been described as "the leading aeronautical journal of the world" around 1910.
History and contents
''L’Aérophile'' was founded and r ...
'', in 1903. This prompted Esnault-Pelterie, a French military engineer, to build a Wright-style glider in 1904 that used ailerons in lieu of
wing warping
Wing warping was an early system for lateral (roll) control of a fixed-wing aircraft. The technique, used and patented by the Wright brothers, consisted of a system of pulleys and cables to twist the trailing edges of the wings in opposite direc ...
.
The French journal ''L'Aérophile'' then published photos of the ailerons on Esnault-Pelterie's glider which were included in his June 1905 article, and its ailerons were widely copied afterward.
The Wright brothers used wing warping instead of ailerons for roll control on their glider in 1902, and about 1904 their
Flyer II was the only aircraft of its time able to do a coordinated banked turn. During the early years of powered flight the Wrights had better roll control on their designs than airplanes that used movable surfaces. From 1908, as aileron designs were refined it became clear that ailerons were much more effective and practical than wing warping. Ailerons also had the advantage of not weakening the airplane's wing structure as did the wing warping technique,
which was one reason for Esnault-Pelterie's decision to switch to ailerons.
By 1911 most biplanes used ailerons rather than wing warping—by 1915 ailerons had become almost universal on monoplanes as well. The U.S. Government, frustrated by the lack of its country's aeronautical advances in the years leading up to
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
, enforced a patent pool effectively putting an end to the
Wright brothers patent war
The Wright brothers patent war centers on the patent they received for their method of airplane flight control. The Wright brothers were two Americans who are widely credited with inventing and building the world's first flyable airplane and mak ...
.
The Wright company quietly changed its aircraft flight controls from wing warping to the use of ailerons at that time as well.
Other early aileron designers
Others who were previously thought to have been the first to introduce ailerons included:
* American
John J. Montgomery
John Joseph Montgomery (February 15, 1858 – October 31, 1911) was an American inventor, physicist, engineer, and professor at Santa Clara University in Santa Clara, California, who is best known for his invention of controlled heavier-than-air ...
included spring-loaded trailing edge flaps on his second glider (1885): these were operable by the pilot as ailerons. In 1886 his third glider design used rotation of the entire wing rather than just a trailing edge portion for roll control. By his own accounts all of these changes in addition to his use of an elevator for pitch control provided "entire control of the machine in the wind, preventing it from upsetting."
* New Zealander
Richard Pearse
Richard William Pearse (3 December 187729 July 1953) was a New Zealand farmer and inventor who performed pioneering aviation experiments. Witnesses interviewed many years afterward describe observing Pearse flying and landing a powered heavie ...
reputedly made a powered flight in a monoplane that included small ailerons as early as 1902, but his claims are controversial—and sometimes inconsistent—and, even by his own reports, his aircraft were not well controlled.
![Bulgarien Farman M](https://upload.wikimedia.org/wikipedia/commons/4/4d/Bulgarien_Farman_M.F.7.jpg)
* In 1906
Alberto Santos-Dumont
Alberto Santos-Dumont ( Palmira, 20 July 1873 — Guarujá, 23 July 1932) was a Brazilian aeronaut, sportsman, inventor, and one of the few people to have contributed significantly to the early development of both lighter-than-air and heavie ...
's
14-bis was one of the earliest (if not ''the'' earliest) engine-powered, aileron-equipped aircraft to fly, as it was modified to have added octagonal-planform interplane ailerons in its outermost wing bays
on November 12 of that year for its concluding flight sessions at the
Chateau de Bagatelle's grounds; but those roll control surfaces were not true "trailing-edge" ailerons hinged directly to the wing panels' framework—for the 14-bis, these were instead pivoted around a horizontal axis centred on the ''forward'' outboard interplane struts, and protruded forward past the wings' leading edges - said to be very much like those on
Robert Esnault-Pelterie Robert Albert Charles Esnault-Pelterie (8 November 1881 – 6 December 1957) was a French aircraft designer and spaceflight theorist. He is referred to as being one of the founders of modern rocketry and astronautics, along with the Russian Kons ...
's 1904 biplane glider design.
* On May 18, 1908, engineer and aircraft designer
Frederick Baldwin, a member of the
Aerial Experiment Association
The Aerial Experiment Association (AEA) was a Canadian-American aeronautical research group formed on 30 September 1907, under the leadership of Dr. Alexander Graham Bell.
The AEA produced several different aircraft in quick succession, with eac ...
headed by
Alexander Graham Bell, flew their first aileron-controlled aircraft, the
AEA White Wing
The White Wing (or Aerodrome #2) was an early US aircraft designed by Frederick W. Baldwin and built by the Aerial Experiment Association in 1908. Unusual for aircraft of its day, it featured a wheeled undercarriage. The wings were equipped with ...
,
which was later copied by the U.S. aeronautical pioneer
Glenn Curtiss
Glenn Hammond Curtiss (May 21, 1878 – July 23, 1930) was an American aviation and motorcycling pioneer, and a founder of the U.S. aircraft industry. He began his career as a bicycle racer and builder before moving on to motorcycles. As early ...
the same year, with the
AEA ''June Bug''.
*
Henry Farman
Henri Farman (26 May 1874– 17 July 1958) was a British-French aviator and aircraft designer and manufacturer with his brother Maurice Farman. Before dedicating himself to aviation he gained fame as a sportsman, specifically in cycling and moto ...
's ailerons on his 1909
Farman III were the first to resemble ailerons on modern aircraft as they were hinged directly to the wing planform structure, and thus were viewed as having a reasonable claim as the ancestor of the modern-day aileron.
* Wingtip ailerons were also used on the contemporary
Bleriot VIII—the first known flightworthy aircraft to use the joystick and rudder bar pioneering form of
modern flight controls in a single airframe, and the 1911-vintage
Curtiss Model D
The 1911 Curtiss Model D (or frequently "Curtiss Pusher") was an early United States pusher aircraft with the engine and propeller behind the pilot's seat. It was among the first aircraft in the world to be built in any quantity, during an era ...
pusher biplane had spanwise rectangular interplane ailerons of a similar nature to those on the final form of the
Santos-Dumont 14-bis
The ''14-bis'' (french: Quatorze-bis), (), also known as ("bird of prey" in French), was a pioneer era, canard-style biplane designed and built by Brazilian aviation pioneer Alberto Santos-Dumont. In 1906, near Paris, the ''14-bis'' made a m ...
,
but mounted on, and pivoted from the outer ''rear'' interplane struts instead.
* Another very late contestant included the American,
William Whitney Christmas
William Whitney Christmas, M.D. (September 1, 1865 – April 14, 1960) was a physician, pioneer aviator, and supposed con man. He was one of many claimants for an early design of the aileron. He was a vice-president of the General Development C ...
, who claimed to have invented the aileron in the 1914 patent for what would become the
Christmas Bullet
The Christmas Bullet, later known as the Cantilever Aero Bullet (sometimes referred to as the Christmas Strutless Biplane), was an American single-seat cantilever wing biplane. It is considered by many to be among the worst aircraft ever construc ...
which was built in 1918.
Both "Bullet" prototypes crashed during their first "flights" when their wings broke off in flight due to
flutter as a result of being deliberately unbraced.
Patents and lawsuits
The Wright Brothers' Ohio patent attorney
Henry Toulmin filed an expansive patent application and on May 22, 1906, the brothers were granted U.S. Patent 821393.
The patent's importance lay in its claim of a new and useful method of ''controlling'' an airplane. The patent application included the claim for the lateral control of aircraft flight that was not limited to wing warping, but through any manipulation of the "....angular relations of the lateral margins of the airplanes
ings
''Ings'' is an old word of Old English origin referring to water meadows and marshes.
The term appears in place names in Yorkshire (such as Hall Ings, Bradford, Fairburn Ings RSPB reserve, Clifton Ings in York, Derwent Ings, Sutton Ings, A ...
... varied in opposite directions". Thus the patent explicitly stated that other methods besides wing-warping could be used for adjusting the outer portions of an airplane's wings to different angles on its right and left sides to achieve lateral roll control.
John J. Montgomery
John Joseph Montgomery (February 15, 1858 – October 31, 1911) was an American inventor, physicist, engineer, and professor at Santa Clara University in Santa Clara, California, who is best known for his invention of controlled heavier-than-air ...
was granted U.S. Patent 831173 at nearly the same time for his methods of wing warping. Both the Wright Brothers patent and Montgomery's patent were reviewed and approved by the same patent examiner at the United States Patent Office, William Townsend. At the time Townsend indicated that both methods of wing warping were invented independently and were sufficiently different to each justify their own patent award.
Multiple U.S. court decisions favoured the expansive Wright patent, which the Wright Brothers sought to enforce with licensing fees starting from $1,000 per airplane,
and said to range up to $1,000 per day.
According to Louis S. Casey, a former curator of the
Smithsonian Air & Space Museum in Washington, D.C., and other researchers, due to the patent they had received the Wrights stood firmly on the position that all flying using lateral roll control, anywhere in the world, would only be conducted under license by them.
The Wrights subsequently became embroiled with numerous lawsuits they launched against aircraft builders who used lateral flight controls, and the brothers were consequently blamed for playing "...a major role in the lack of growth and aviation industry competition in the United States comparative to other nations like Germany leading up to and during World War I".
Years of protracted legal conflict ensued with many other aircraft builders until the U.S. entered World War I, when the government imposed a legislated agreement among the parties which resulted in royalty payments of 1% to the Wrights.
Ongoing controversy
There are still conflicting claims today over who first invented the aileron. Other 19th century engineers and scientists, including
Charles Renard,
Alphonse Pénaud
Alphonse Pénaud (31 May 1850 – 22 October 1880), was a 19th-century French pioneer of aviation design and engineering. He was the originator of the use of twisted rubber to power model aircraft, and his 1871 model airplane, which he called ...
, and
Louis Mouillard Louis may refer to:
* Louis (coin)
* Louis (given name), origin and several individuals with this name
* Louis (surname)
* Louis (singer), Serbian singer
* HMS ''Louis'', two ships of the Royal Navy
See also
Derived or associated terms
* Lewis (d ...
, had described similar flight control surfaces. Another technique for lateral flight control,
wing warping
Wing warping was an early system for lateral (roll) control of a fixed-wing aircraft. The technique, used and patented by the Wright brothers, consisted of a system of pulleys and cables to twist the trailing edges of the wings in opposite direc ...
, was also described or experimented with by several people including
Jean-Marie Le Bris
Jean Marie Le Bris (March 25, 1817, Concarneau – February 17, 1872, Douarnenez) was a French aviator, born in Concarneau, Brittany who built two glider aircraft and performed at least one flight on board of his first machine in late 1856. His ...
,
John Montgomery,
Clement Ader
Clement or Clément may refer to:
People
* Clement (name), a given name and surname
* Saint Clement (disambiguation)#People
Places
* Clément, French Guiana, a town
* Clement, Missouri, U.S.
* Clement Township, Michigan, U.S.
Other uses
* Ad ...
,
Edson Gallaudet, D.D. Wells, and Hugo Mattullath.
Aviation historian
C.H. Gibbs-Smith wrote that the aileron was "....one of the most remarkable inventions... of aeronautical history, which was immediately lost sight of".
In 1906 the
Wright brothers obtained a patent not for the invention of an airplane (which had existed for a number of decades in the form of gliders) but for the invention of a system of aerodynamic control that manipulated a flying machine's surfaces, including lateral flight control,
although
rudders
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally air or water). On an aircraft the rudder is used primarily to counter adverse ya ...
,
elevators
An elevator or lift is a cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or decks of a building, vessel, or other structure. They are ...
and ailerons had previously been invented.
Flight dynamics
![Flight](https://upload.wikimedia.org/wikipedia/commons/6/60/Flight._Yak-52_%288169897047%29.jpg)
Pairs of ailerons are typically interconnected so that when one is moved downward, the other is moved upward: the down-going aileron increases the
lift
Lift or LIFT may refer to:
Physical devices
* Elevator, or lift, a device used for raising and lowering people or goods
** Paternoster lift, a type of lift using a continuous chain of cars which do not stop
** Patient lift, or Hoyer lift, mobil ...
on its wing while the up-going aileron reduces the lift on its wing, producing a rolling (also called 'banking')
moment about the aircraft's longitudinal axis (which extends from the nose to the tail of an airplane).
Ailerons are usually situated near the
wing tip
A wing tip (or wingtip) is the part of the wing that is most distant from the fuselage of a fixed-wing aircraft.
Because the wing tip shape influences the size and drag of the wingtip vortices, tip design has produced a diversity of sha ...
, but may sometimes also be situated nearer the
wing root
The wing root is the part of the wing on a fixed-wing aircraft or winged-spaceship that is closest to the fuselage
The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, o ...
. Modern airliners may also have a second pair of ailerons on their wings, with the two positions distinguished by the terms 'outboard aileron' and 'inboard aileron'.
An unwanted side effect of aileron operation is
adverse yaw Adverse yaw is the natural and undesirable tendency for an aircraft to yaw in the opposite direction of a roll. It is caused by the difference in lift and drag of each wing. The effect can be greatly minimized with ailerons deliberately designed to ...
—a
yawing moment in the opposite direction to the roll. Using the ailerons to roll an aircraft to the right produces a yawing motion to the left. As the aircraft rolls, adverse yaw is caused partly by the change in
drag between the left and right wing. The rising wing generates increased lift, which causes increased
induced drag
In aerodynamics, lift-induced drag, induced drag, vortex drag, or sometimes drag due to lift, is an aerodynamic drag force that occurs whenever a moving object redirects the airflow coming at it. This drag force occurs in airplanes due to wings or ...
. The descending wing generates reduced lift, which causes reduced induced drag. Profile drag caused by the deflected ailerons may add further to the difference, along with changes in the lift vectors as one rotates back while the other rotates forward.
![1937 Waco VKS-7 CAvM Ottawa,ON MDF 8398](https://upload.wikimedia.org/wikipedia/commons/7/7c/1937_Waco_VKS-7_CAvM_Ottawa%2CON_MDF_8398.jpg)
In a
coordinated turn, adverse yaw is effectively compensated by the use of the
rudder
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally aircraft, air or watercraft, water). On an aircraft the rudder is used primarily to ...
, which results in a sideforce on the vertical tail that opposes the adverse yaw by creating a favorable yawing moment. Another method of compensation is '
differential ailerons', which have been rigged so that the down-going aileron deflects less than the up-going one. In this case the opposing yaw moment is generated by a difference in
profile drag
Parasitic drag, also known as profile drag, is a type of aerodynamic drag that acts on any object when the object is moving through a fluid. Parasitic drag is a combination of form drag and skin friction drag. It affects all objects regardless of ...
between the left and right wingtips. ''Frise ailerons'' accentuate this profile drag imbalance by protruding beneath the wing of an upward-deflected aileron, most often by being hinged slightly behind the leading edge and near the bottom of the surface, with the lower section of the aileron surface's leading edge protruding slightly below the wing's undersurface when the aileron is deflected upwards, substantially increasing profile drag on that side. Ailerons may also be designed to use a combination of these methods.
With ailerons in the neutral position, the wing on the outside of the turn develops more lift than the opposite wing due to the variation in airspeed across the wing span, which tends to cause the aircraft to continue to roll. Once the desired
angle of bank
A banked turn (or banking turn) is a turn or change of direction in which the vehicle banks or inclines, usually towards the inside of the turn. For a road or railroad this is usually due to the roadbed having a transverse down-slope towards the ...
(degree of rotation about the longitudinal axis) has been obtained, the pilot uses opposite aileron to prevent the angle of bank from increasing due to this variation in lift across the wing span. This minor opposite use of the control must be maintained throughout the turn. The pilot also uses a slight amount of
rudder
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally aircraft, air or watercraft, water). On an aircraft the rudder is used primarily to ...
in the same direction as the turn to counteract adverse yaw and to produce a "coordinated" turn wherein the
fuselage
The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraft t ...
is parallel to the flight path. A simple gauge on the instrument panel called the
slip indicator
In aviation, the turn and slip indicator (T/S, a.k.a. turn and bank indicator) and the turn coordinator (TC) variant are essentially two aircraft flight instruments in one device. One indicates the rate of turn, or the rate of change in the aircr ...
, also known as "the ball", indicates when this coordination is achieved.
Aileron components
Horns and aerodynamic counterbalances
![Fokker Dr](https://upload.wikimedia.org/wikipedia/commons/1/17/Fokker_Dr._I_%28117710246%29.jpg)
Particularly on larger or faster aircraft, control forces may be extremely heavy. Borrowing a discovery from boats that extending a control surface's area forward of the hinge lightens the forces needed first appeared on ailerons during World War I when ailerons were extended beyond the wingtip and provided with a horn ahead of the hinge. Known as overhung ailerons, possibly the best known examples are the
Fokker Dr.I
The Fokker Dr.I (''Dreidecker'', "triplane" in German), often known simply as the Fokker Triplane, was a World War I fighter aircraft built by Fokker-Flugzeugwerke. The Dr.I saw widespread service in the spring of 1918. It became famous as the ...
and
Fokker D.VII
The Fokker D.VII was a German World War I fighter aircraft designed by Reinhold Platz of the Fokker-Flugzeugwerke. Germany produced around 3,300 D.VII aircraft in the second half of 1918. In service with the ''Luftstreitkräfte'', the D.VII qui ...
. Later examples brought the counterbalance in line with the wing to improve control and reduce drag. This is seen less often now, due to the Frise type aileron which provides the same benefit.
Trim tabs
Trim tabs are small movable sections resembling scaled down ailerons located at or near the trailing edge of the aileron. On most propeller powered aircraft, the rotation of the propeller(s) induces a counteracting roll movement due to
Newton's third law of motion
Newton's laws of motion are three basic laws of classical mechanics that describe the relationship between the motion of an object and the forces acting on it. These laws can be paraphrased as follows:
# A body remains at rest, or in motio ...
, in that every action has an equal and opposite reaction. To relieve the pilot of having to provide continuous pressure on the stick in one direction (which causes fatigue) trim tabs are provided to adjust or ''trim out'' the pressure needed against any unwanted movement. The tab itself is deflected in relation to the aileron, causing the aileron to move in the opposite direction. Trim tabs come in two forms, adjustable and fixed. A fixed trim tab is manually bent to the required amount of deflection, while the adjustable trim tab can be controlled from within the cockpit so that different power settings or flight attitudes can be compensated for. Some large aircraft from the 1950s (including the
Canadair Argus
The Canadair CP-107 Argus (company designation CL-28) is a maritime patrol aircraft designed and manufactured by Canadair for the Royal Canadian Air Force (RCAF). In its early years, the Argus was reputedly the finest anti-submarine patrol bomb ...
) used free floating control surfaces that the pilot controlled only through the deflection of trim tabs, in which case additional tabs were also provided to fine-tune the control to provide straight and level flight.
Spades
![Extra 300L aircraft D-EXFF 2009 03](https://upload.wikimedia.org/wikipedia/commons/3/3a/Extra_300L_aircraft_D-EXFF_2009_03.jpg)
Spades are flat metal plates, usually attached to the aileron lower surface, ahead of the aileron hinge, by a lever arm. They reduce the force needed by the pilot to deflect the aileron and are often seen on
aerobatic
Aerobatics is the practice of flying maneuvers involving aircraft attitudes that are not used in conventional passenger-carrying flights. The term is a portmanteau of "aerial" and "acrobatics". Aerobatics are performed in aeroplanes and glid ...
aircraft. As the aileron is deflected upward, the spade produces a downward aerodynamic force, which tends to rotate the whole assembly so as to further deflect the aileron upward. The size of the spade (and its lever arm) determines how much force the pilot needs to apply to deflect the aileron. A spade works in the same manner as a horn but is more efficient due to the longer
moment arm
In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of ...
.
Mass balance weights
![Mass Balancing ME Bf110](https://upload.wikimedia.org/wikipedia/commons/0/0f/Mass_Balancing_ME_Bf110.jpg)
To increase the speed at which control surface flutter (
aeroelastic flutter
Aeroelasticity is the branch of physics and engineering studying the interactions between the inertial, elastic, and aerodynamic forces occurring while an elastic body is exposed to a fluid flow. The study of aeroelasticity may be broadly classif ...
) might become a risk, the
center of gravity
In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force ma ...
of the control surface is moved towards the hinge-line for that surface. To achieve this, lead weights may be added to the front of the aileron. In some aircraft the aileron construction may be too heavy to allow this system to work without an excessive increase in the weight of the aileron. In this case, the weight may be added to a lever arm to move the weight well out in front to the aileron body. These balance weights are tear drop shaped (to reduce drag), which make them appear quite different from spades, although both project forward and below the aileron. In addition to reducing the risk of flutter, mass balances also reduce the stick forces required to move the control surface in maneuvers.
Aileron fences
Some aileron designs, particularly when fitted on swept wings, include fences like
wing fence
Wing fences, also known as boundary layer fences and potential fences are fixed aerodynamic devices attached to aircraft wings. Often seen on swept-wing aircraft, wing fences are flat plates fixed to the upper surfaces parallel to the wing ch ...
s flush with their inboard plane, in order to suppress some of the spanwise component of the airflow running on the top of the wing, which tends to disrupt the laminar flow above the aileron, when deflected downwards.
Types of ailerons
Single acting ailerons
Used during
aviation's pre-war "pioneer era" and into the early years of the First World War, these ailerons were each controlled by a single cable, which pulled the aileron up. When the aircraft was at rest, the ailerons hung vertically down. This type of aileron was used on the
Farman III biplane 1909 and the
Short 166. A "reverse" version of this, utilizing wing-warping, existed on the
later version of the Santos-Dumont ''Demoiselle'', which only warped the wingtips "downward". One of the disadvantages of this setup was a greater tendency to yaw than even with basic interconnected ailerons.
During the 1930s a number of light aircraft used single acting controls but used springs to return the ailerons to their neutral positions when the stick was released.
Wingtip ailerons
![Sports Aviation - Issy-les-Moulineaux (10 septembre) - Le Blériot VIII … (7843390842)](https://upload.wikimedia.org/wikipedia/commons/4/40/Sports_Aviation_-_Issy-les-Moulineaux_%2810_septembre%29_-_Le_Bl%C3%A9riot_VIII_%E2%80%A6_%287843390842%29.jpg)
Used on the first-ever airframe to have the combination of "joystick/rudder-bar" controls that directly led to the modern
flight control system
A conventional fixed-wing aircraft flight control system consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. Aircraft ...
, the
Blériot VIII
The Blériot VIII was a French pioneer era aeroplane built by Louis Blériot, significant for its adoption of both a configuration and a control system that were to set a standard for decades to come.
Design and development
The previous year, ...
in 1908, some designs of early aircraft used "wingtip" ailerons, where the entire wingtip was rotated to achieve roll control as a separate, pivoting roll-control surface—the
AEA June Bug
The ''June Bug'' (or ''Aerodrome #3'') was an American "pioneer era" aircraft designed and flown by Glenn H. Curtiss and built by the Aerial Experiment Association (A.E.A) in 1908. The ''June Bug'' is famous for winning the first aeronautical ...
used a form of these, with both the experimental German
Fokker V.1 of 1916 and the earlier versions of the Junkers J 7 all-duralumin metal demonstrator monoplane using them—the J 7 led directly to the
Junkers D.I all-duralumin metal German fighter design of 1918, which had conventionally hinged ailerons. The main problem with this type of aileron is the dangerous tendency to
stall if used aggressively, especially if the aircraft is already in danger of stalling, hence the use primarily on prototypes, and their replacement on production aircraft with more conventional ailerons.
Frise ailerons
Engineer
Leslie George Frise (1897–1979) of the
Bristol Aeroplane Company developed an aileron shape that is pivoted at about its 25 to 30% chord line and near its bottom surfac
in order to decrease stick forces as aircraft became faster during the 1930s. When the aileron is deflected up (to make its wing go down), the leading edge of the aileron starts to protrude below the underside of the wing into the airflow beneath the wing. The moment of the leading edge in the airflow helps to move up the trailing edge, which decreases the stick force. The down moving aileron also adds energy to the boundary layer. The edge of the aileron directs air flow from the underside of the wing to the upper surface of the aileron, thus creating a lifting force added to the lift of the wing. This reduces the needed deflection of the aileron. Both the Canadian
Fleet Model 1, Fleet Model 2 biplane of 1930 and the 1938 popular US
Piper J-3 Cub
The Piper J-3 Cub is an American light aircraft that was built between 1938 and 1947 by Piper Aircraft. The aircraft has a simple, lightweight design which gives it good low-speed handling properties and short-field performance. The Cub is Pi ...
monoplane possessed Frise ailerons as designed and helped introduce them to a wide audience.
A claimed benefit of the Frise aileron is the ability to counteract adverse yaw. To do so, the leading edge of the aileron has to be sharp or bluntly rounded, which adds significant drag to the upturned aileron and helps counterbalance the yaw force created by the other aileron turned down. This can add some unpleasant, nonlinear effect and/or potentially dangerous aerodynamic vibration (flutter). Adverse yaw moment is basically countered by aircraft yaw stability and also by the use of differential aileron movement.
Differential ailerons
By careful design of the mechanical linkages, the up aileron can be made to deflect more than the down aileron (e.g., US patent 1,565,097). This helps reduce the likelihood of a wing tip
stall when aileron deflections are made at high angles of attack. In addition, the consequent differential in drag reduces
adverse yaw Adverse yaw is the natural and undesirable tendency for an aircraft to yaw in the opposite direction of a roll. It is caused by the difference in lift and drag of each wing. The effect can be greatly minimized with ailerons deliberately designed to ...
(as also discussed
above). The idea is that the loss of lift associated with the up aileron carries no penalty while the increase in lift associated with the down aileron is minimized. The rolling
couple
Couple or couples may refer to :
Basic meaning
*Couple (app), a mobile app which provides a mobile messaging service for two people
*Couple (mechanics), a system of forces with a resultant moment but no resultant force
*Couple (relationship), tw ...
on the aircraft is always the difference in lift between the two wings. A designer at
de Havilland
The de Havilland Aircraft Company Limited () was a British aviation manufacturer established in late 1920 by Geoffrey de Havilland at Stag Lane Aerodrome Edgware on the outskirts of north London. Operations were later moved to Hatfield in H ...
invented a simple and practical linkage and their
de Havilland Tiger Moth
The de Havilland DH.82 Tiger Moth is a 1930s British biplane designed by Geoffrey de Havilland and built by the de Havilland Aircraft Company. It was operated by the Royal Air Force (RAF) and other operators as a primary trainer aircraft. ...
classic British
biplane
A biplane is a fixed-wing aircraft with two main wings stacked one above the other. The first powered, controlled aeroplane to fly, the Wright Flyer, used a biplane wing arrangement, as did many aircraft in the early years of aviation. While ...
became one of the best-known aircraft, and one of the earliest, to use differential ailerons.
Roll control without ailerons
Wing warping
On the earliest
Pioneer Era aircraft, such as the
Wright Flyer
The ''Wright Flyer'' (also known as the ''Kitty Hawk'', ''Flyer'' I or the 1903 ''Flyer'') made the first sustained flight by a manned heavier-than-air powered and controlled aircraft—an airplane—on December 17, 1903. Invented and flown b ...
and the later, 1909-origin
Blériot XI
The Blériot XI is a French aircraft of the pioneer era of aviation. The first example was used by Louis Blériot to make the first flight across the English Channel in a heavier-than-air aircraft, on 25 July 1909. This is one of the most fa ...
and
Etrich Taube
The Etrich ''Taube'', also known by the names of the various later manufacturers who built versions of the type, such as the Rumpler ''Taube'', was a pre-World War I monoplane aircraft. It was the first military aeroplane to be mass-produced in ...
, lateral control was effected by twisting the outboard portion of the wing so as to increase or decrease lift by changing the angle of attack. This had the disadvantages of stressing the structure, being heavy on the controls, and of risking stalling the side with the increased angle of attack during a maneuver. By 1916, most designers had abandoned wing warping in favor of ailerons. Researchers at
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
and elsewhere have been taking a second look at wing warping again, although under new names. The NASA version is the
X-53 Active Aeroelastic Wing
The X-53 Active Aeroelastic Wing (AAW) development program is a completed American research project that was undertaken jointly by the Air Force Research Laboratory (AFRL), Boeing Phantom Works and NASA's Dryden Flight Research Center, where t ...
while the
United States Air Force
The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal ...
tested the
Adaptive Compliant Wing
An adaptive compliant wing is a wing which is flexible enough for aspects of its shape to be changed in flight. Flexible wings have a number of benefits. Conventional flight control mechanisms operate using hinges, resulting in disruptions to the ...
.
Differential spoilers
Spoilers are devices that when extended into the airflow over a wing, disrupt the airflow and reduce the amount of lift generated. Many modern aircraft designs, especially
jet aircraft
A jet aircraft (or simply jet) is an aircraft (nearly always a fixed-wing aircraft) propelled by jet engines.
Whereas the engines in propeller-powered aircraft generally achieve their maximum efficiency at much lower speeds and altitudes, je ...
, use spoilers in lieu of, or to supplement ailerons, such as the
F4 Phantom II
The McDonnell Douglas F-4 Phantom II is an American tandem two-seat, twin-engine, all-weather, long-range supersonic jet interceptor and fighter-bomber originally developed by McDonnell Aircraft for the United States Navy.Swanborough and ...
and
Northrop P-61 Black Widow
The Northrop P-61 Black Widow is a twin-engine United States Army Air Forces fighter aircraft of World War II. It was the first operational U.S. warplane designed as a night fighter, and the first aircraft designed specifically as a night figh ...
, which had almost full width flaps (there were very small conventional ailerons at the wingtips as well).
Roll induced by rudder
All aircraft with dihedral have some form of yaw-roll coupling to promote stability. Common trainers like the Cessna 152/172 series can be roll controlled with rudder alone. The rudder of the Boeing 737 has more roll authority over the aircraft than the ailerons at high angles of attack. This led to two notable accidents when the rudder jammed in the fully deflected position causing rollovers (see
Boeing 737 rudder issues
During the 1990s, a series of issues affecting the rudder of Boeing 737 passenger aircraft resulted in multiple incidents. In two separate accidents, pilots lost control of their aircraft due to a sudden and unexpected rudder movement, and the re ...
).
Some aircraft such as the
Fokker Spin
The Fokker ''Spin'' was the first airplane built by Dutch aviation pioneer Anthony Fokker. The many bracing wires used to strengthen the aircraft made it resemble a giant spider, hence its name ''Spin'', Dutch for "spider".
Fokker built the ''Sp ...
and model gliders lack any type of lateral control. Those aircraft use a higher amount of dihedral than conventional aircraft. Deflecting the rudder gives yaw and a lot of differential wing lift, giving a yaw induced roll moment. This type of control system is most commonly seen in the
Flying Flea
The Flying Flea (french: Pou du Ciel, lit=Louse of the Sky) is a large family of light homebuilt aircraft first flown in 1933.
The odd name comes from the French nickname for the Ford Model T automobile: ''Pou de la Route'', or "Louse of the Ro ...
family of small aircraft and on simpler 2-function (pitch and yaw control) glider models or 3-function (pitch, yaw and throttle control) model powered aircraft, such as radio-controlled versions of
"Old Timer" free-flight engine-powered model aircraft.
Other methods
*
Weight-shift control
Weight-shift control as a means of aircraft flight control is widely used in hang gliders, powered hang gliders, and ultralight trikes. Control is usually by the pilot using their weight against a triangular control bar that is rigidly attached ...
is widely used in hang gliders, powered hang gliders, and ultralight aircraft.
*
Flight with disabled controls has been successful in a small number of aviation incidents.
*
Reaction control valves as used in the
Harrier family of military aircraft.
*Top rudder: this device was fitted to the
British Army Aeroplane No 1
The British Army Aeroplane No 1 or sometimes Cody 1 was a biplane built by Samuel Franklin Cody in 1907 at the Army Balloon Factory at Farnborough. It made the first recognised powered and sustained flight in the United Kingdom on 16 October 19 ...
. It comprised an all-flying fin mounted above the upper wing and pivoted about a vertical axis. In operation it applied a side force approximately above the centre of pressure, causing the craft to roll. The design also had all-flying ailerons between the wing planes, but these were removed at the time it made the first official flight of a British aircraft and roll control during the flight was achieved solely by use of the top rudder.
Combinations with other control surfaces
![F-16 4 Yokota Tokyo](https://upload.wikimedia.org/wikipedia/commons/0/04/F-16_4_Yokota_Tokyo.jpg)
* A control surface that combines an aileron and
flap
Flap may refer to:
Arts, entertainment, and media
* ''Flap'' (film), a 1970 American film
* Flap, a boss character in the arcade game ''Gaiapolis''
* Flap, a minor character in the film '' Little Nemo: Adventures in Slumberland''
Biology and he ...
is called a ''
flaperon
A flaperon (a portmanteau of flap and aileron) on an aircraft's wing is a type of control surface that combines the functions of both flaps and ailerons. Some smaller kitplanes have flaperons for reasons of simplicity of manufacture, while ...
''. A single surface on each wing serves both purposes: Used as an aileron, the flaperons left and right are actuated differentially; when used as a flap, both flaperons are actuated downwards. When a flaperon is actuated downward (i.e., used as a flap), there is enough freedom of movement left to be able to still use the aileron function.
* Some aircraft have used differentially controlled
spoilers or ''
spoileron
In aeronautics, spoilerons (also known as spoiler ailerons or roll spoilers) are spoilers that can be used asymmetrically as flight control surfaces to provide roll control.
Operation
Spoilerons roll an aircraft by reducing the lift of the ...
s'' to provide roll instead of conventional ailerons. The advantage is that the entire trailing edge of the wing may be devoted to flaps, providing better low speed control. The
Northrop P-61 Black Widow
The Northrop P-61 Black Widow is a twin-engine United States Army Air Forces fighter aircraft of World War II. It was the first operational U.S. warplane designed as a night fighter, and the first aircraft designed specifically as a night figh ...
used spoilers in this manner, in conjunction with full span zap flaps and some modern airliners use spoilers to assist the ailerons.
* On
delta-wing
A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ).
Although long studied, it did not find significant applications until the Jet Age, when it proved suitab ...
ed aircraft, the ailerons are combined with the
elevators
An elevator or lift is a cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or decks of a building, vessel, or other structure. They are ...
to form an ''
elevon
Elevons or tailerons are aircraft control surfaces that combine the functions of the elevator (used for pitch control) and the aileron (used for roll control), hence the name. They are frequently used on tailless aircraft such as flying wings. A ...
''.
* Several modern fighter aircraft may have no ailerons on their wings but provide roll control with an all moving horizontal tailplane. When horizontal tailplane
stabilators can move differentially to perform the
roll
Roll or Rolls may refer to:
Movement about the longitudinal axis
* Roll angle (or roll rotation), one of the 3 angular degrees of freedom of any stiff body (for example a vehicle), describing motion about the longitudinal axis
** Roll (aviation), ...
control function of ailerons, as they do on some modern
fighter aircraft
Fighter aircraft are fixed-wing military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air superiority of the battlespace. Domination of the airspace above a battlefield ...
, they are termed 'tailerons' or 'rolling tails'. Tailerons additionally permit wider flaps on the aircraft's wings.
* Aileron struts combined movable surfaces with an airfoil shaped wing strut. Acting in the propeller slipstream increased their effectiveness, although their mechanical advantage is lowered due to the inboard location.
See also
*
Aircraft flight control system
A conventional fixed-wing aircraft flight control system consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. Aircraft ...
*
Elevator (aeronautics)
Elevators are flight control surfaces, usually at the rear of an aircraft, which control the aircraft's pitch, and therefore the angle of attack and the lift of the wing. The elevators are usually hinged to the tailplane or horizontal stab ...
*
Flap
Flap may refer to:
Arts, entertainment, and media
* ''Flap'' (film), a 1970 American film
* Flap, a boss character in the arcade game ''Gaiapolis''
* Flap, a minor character in the film '' Little Nemo: Adventures in Slumberland''
Biology and he ...
*
Flaperon
A flaperon (a portmanteau of flap and aileron) on an aircraft's wing is a type of control surface that combines the functions of both flaps and ailerons. Some smaller kitplanes have flaperons for reasons of simplicity of manufacture, while ...
, a control surface combining both a flap and an aileron
*
Spoiler
Spoiler is a security vulnerability on modern computer central processing units that use speculative execution. It exploits side-effects of speculative execution to improve the efficiency of Rowhammer and other related memory and cache attacks. Ac ...
, a flight control surface occasionally confused with ailerons
*
Rudder
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally aircraft, air or watercraft, water). On an aircraft the rudder is used primarily to ...
*
Trailing edge
The trailing edge of an aerodynamic surface such as a wing 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. ...
*
The Wright brothers patent war
The Wright brothers patent war centers on the patent they received for their method of airplane flight control. The Wright brothers were two Americans who are widely credited with inventing and building the world's first flyable airplane and mak ...
References
Footnotes
Citations
Bibliography
* Bullmer, Joe.
''The WRight Story: The True Story of the Wright Brothers' Contribution to Early Aviation'' CreateSpace Independent Publishing Platform, , , 2009.
* Casey, Louis S
''Curtiss, The Hammondsport Era, 1907–1915'' New York: Crown Publishers, 1981, pp. 12–15, , .
* Parkin, John H
''Bell and Baldwin: Their Development of Aerodromes and Hydrodromes at Baddeck, Nova Scotia'' Toronto: University of Toronto Press, 1964.
External links
with Java demo and more pictures
{{Aircraft components
Aircraft controls
Aircraft wing components