How ailerons create a rolling moment

Aileron - Aileron

Aircraft control surface to induce roll
An airplane that "rolls" or "banks" with its ailerons

A Ailerons (French for "small wing" or "fin") is a pivoting flight control surface that is usually part of the trailing edge of each wing on a fixed-wing aircraft. Ailerons are used in pairs to steer the aircraft in roll (or moving around the aircraft's longitudinal axis), which usually results in a change in flight path due to the slope of the lift vector. Movement about this axis is called "rolling" or "banking".

There is considerable controversy over the recognition of the invention of the aileron. The Wright brothers and Glenn Curtiss fought a long-standing legal battle over the Wright patent of 1906, which described a method of wing warping to achieve lateral control. The brothers prevailed in several court rulings found that Curtiss' use of ailerons violated Wright's patent. Ultimately, World War I forced the US government to come up with a legal solution. A much earlier aileron concept was developed in 1868 by British scientist Matthew Piers Watt Boulton based on his work On Aërial Locomotion by 1864 patented .


Boulton's 1864 paper "On Aërial Locomotion" describes several designs, including ailerons.

The name "aileron" from French, which means "small wing", also refers to the ends of a bird's wings that are used to control flight. It first appeared in print in the 7th edition of Cassell's French-English dictionary from 1877 with the main meaning "little wing". In connection with powered aircraft, it appears in print around 1908. Previously, ailerons were often referred to as rudders, their older technical siblings, with no distinction between orientation and function or more descriptive than horizontal rudder (in French Gouvernails) denotes horizontalaux ). One of the earliest printed aerospace applications of "Aileron" was that in French aviation magazine L'Aérophile by 1908.

Ailerons had more or less completely superseded other forms of lateral control, such as wing warping, by around 1915, long after the function of the rudder and elevator flight controls had been largely standardized. Although there were previously many conflicting claims about who first invented the aileron and its function, i.e. aileron or roll controls, the flight control device was used by British scientist and metaphysicist Matthew Piers Watt Boulton in his work On Aërial Locomotion by Invented and described in 1864. 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 in which we recognized the need for active lateral control as opposed to [passive lateral stability] ... With this Boulton invention, we have the birth of the present three-torque method Air control "as praised by Charles Manly. This was also approved by CH Gibbs-Smith. Boulton's British patent No. 392 of 1868, granted some 35 years before the ailerons "reinvented" in France, was forgotten and went out of sight until the flight controller was widely used. Gibbs-Smith stated on several occasions that if the Boulton patent had been revealed at the time of legal filing by the Wright brothers, it may not have been able to claim the priority of the invention for lateral control of flying machines. The fact that the Wright brothers were able to obtain a patent in 1906 did not invalidate Boulton's lost and forgotten invention.

Ailerons were only used in manned aircraft when they were used on Robert Esnault-Pelterie's glider in 1904. In 1871, a French military engineer, Charles Renard, built and flew an unmanned glider with ailerons on each side (which he referred to as winglets') activated by a pendulum-controlled single-axis Boulton-style autopilot device.

Pioneering US aeronautical engineer Octave Chanute published 1903 descriptions and drawings of the Wright Brothers' glider in the leading aviation magazine of the day, L'Aérophile . This prompted the French military engineer Esnault-Pelterie to build a Wright-. Style glider in 1904 that used ailerons instead of wing deformation. The French magazine L'Aérophile subsequently published photos of the ailerons on Esnault-Pelterie's glider included in his June 1905 article, and the ailerons were subsequently largely copied.

The Wright brothers used wing distortion instead of ailerons to control roll of their glider in 1902, and by 1904 their Flyer II was the only aircraft of its time that could perform a coordinated bank turn. In the early years of powered flight, the Wrights had better roll control on their designs than planes with moving surfaces. From 1908, when aileron designs were refined, it became clear that ailerons were much more effective and practical than wing distortions. Ailerons also had the advantage that the aircraft's wing structure was not weakened, as was the wing warping technique, which was one reason Esnault-Pelterie decided to switch to ailerons.

By 1911, most biplane used ailerons instead of wing deformation - by 1915, ailerons had become almost universal on monoplane as well. The US government, frustrated by the lack of advances in their country's aviation in the years leading up to World War I, pushed through a patent pool that effectively ended the Wright brothers' patent war. The Wright company quietly changed its flight controls from wing distortion to ailerons at this time.

Other early aileron designers

Others previously believed to have been the first to introduce ailerons were:

  • The American John J. Montgomery installed spring-loaded trailing edge flaps in his second glider (1885), which the pilot could use as ailerons. In 1886, his third glider design used rotation of the entire wing, rather than just a trailing edge section, for roll control. According to the company, all of these changes, in addition to its use of an elevator for pitch control, provided "complete control of the machine in the wind to prevent machine malfunction".
  • New Zealander Richard Pearse allegedly made a powered flight in a monoplane with small ailerons as early as 1902, but his claims are controversial - and sometimes inconsistent - and even according to his own reports, his planes were not well controlled.
A 1912 Farman HF.20 biplane with single-acting ailerons hinged from the rear spar. The ailerons hang down when at rest and are pushed into position with air force when flying. They are pulled down with a cable for control.
  • 1906 Alberto Santos-Dumont's 14-bis was one of the earliest aileron-equipped aircraft to fly, as it was modified for its final flight sessions to have eight layout between the ailerons levels added in its outermost wing bays in November of that year Chateau de Bagatelle; However, these roll control surfaces were not real "trailing edge" ailerons that were hinged directly to the frame of the wing plates. In the case of the 14-bis, these were instead swiveled around a horizontal axis that points to the front Outboard interlevel struts were centered, and protruded forward past the wishbones, wing leading edges.
  • On May 18, 1908, engineer and aircraft designer Frederick Baldwin, a member of the Aerial Experiment Association headed by Alexander Graham Bell, flew his first aileron-controlled aircraft, the AEA White Wing, later copied by American aviation pioneer Glenn Curtiss in the same year with the AEA June bug .
  • Henry Farman's ailerons on his 1909 Farman III were the first to resemble ailerons in modern aircraft, as they were hinged directly to the structure of the wing planform and therefore had reasonable claims as the ancestor of the modern aileron.
  • Wingtip ailerons were also used on the contemporary Bleriot VIII - the first known flightworthy aircraft with the joystick and control levers pioneering modern flight controls in a single cell, and the 1911-vintage Curtiss D pusher biplane had spans similar to rectangular between the planes of ailerons Nature as in the final form of the Santos-Dumont 14-bis, but mounted and instead of the outer ones rear Inter-level struts pivoted.
  • Another very late participant was the American William Whitney Christmas, who claimed to have invented the aileron in the 1914 patent for the Christmas bauble built in 1918. Both "Bullet" prototypes crashed on their first "flights" when their wings broke off in flight due to fluttering because they were deliberately not stretched.

Patents and lawsuits

The Wright Brothers Ohio patent attorney, Henry Toulmin, filed a comprehensive patent application and on May 22, 1906, the brothers were granted U.S. Patent 821393. The importance of the patent lay in the requirement for a new and useful method for control of an airplane. The patent application contained the right to lateral control of aircraft flight, which was not limited to wing deformation, but rather through any manipulation of the "... angular relationships of the lateral edges of the aircraft [wings] ... varied in opposite directions". It was therefore expressly stated in the patent that, besides warping the wings, other methods could also be used to adjust the outer parts of the wings of an aircraft at different angles on the right and left sides in order to achieve lateral roll control. Almost at the same time, John J. Montgomery received US Pat. No. 831,173 for his method of warping wings. Both the Wright Brothers patent and the Montgomery patent were examined and approved by the same patent examiner at the US Patent Office, William Townsend. At the time, Townsend stated that both methods of wing warping were invented independently and were sufficiently different from one another to warrant their own patenting.

Several US court rulings endorsed the far-reaching Wright patent, which the Wright Brothers wanted to enforce with license fees starting at USD 1,000 per aircraft and which is said to be up to USD 1,000 per day. According to Louis S. Casey, a former curator of the Smithsonian Air & Space Museum in Washington, DC, and other researchers, because of the patent they received, the Wrights were firmly in the position of anyone with side roll control anywhere in the world fly The world would only be run by them under license.

The Wrights subsequently became embroiled in numerous lawsuits against aircraft manufacturers employing side flight controls, and the brothers were consequently accused of "... playing an important role in the lack of growth and competition in the aviation industry in the United States relative to others play nations like Germany before and during the First World War ". Years of protracted litigation ensued with many other aircraft manufacturers until the U.S. entered World War I when the government imposed a legal agreement between the parties that resulted in 1% royalty payments to the Wrights.

Ongoing controversy

There are still conflicting claims today about who first invented the aileron. Other 19th century engineers and scientists, including Charles Renard, Alphonse Pénaud, and Louis Mouillard, had described similar flight control surfaces. Another technique for lateral flight control, wing warping, has also been described or experimented by several people, including Jean-Marie Le Bris, John Montgomery, Clement Ader, Edson Gallaudet, DD Wells, and Hugo Mattullath. Aviation historian CH Gibbs-Smith wrote that the aileron was "... one of the most remarkable inventions in aviation history that was instantly lost sight of".

In 1906, the Wright brothers received a patent not for the invention of an airplane (which had existed for several decades in the form of gliders), but for the invention of an aerodynamic control system that manipulated the surfaces of a flying machine, including side flight, although previously rudder, Elevators and ailerons had been invented.

Flight dynamics

A Yak-52 that uses ailerons to roll counterclockwise during an aerobatic maneuver

Pairs of ailerons are usually linked together in such a way that moving one down moves the other up: the falling aileron increases lift on its wing, while the rising aileron decreases lift on its wing and creates a roll (also called) "bench" - Moment about the longitudinal axis of the aircraft (which extends from the nose to the tail of an aircraft). Ailerons are usually near the wing tip, but sometimes near the wing root. Modern commercial aircraft can also have a second pair of ailerons on their wings, the two positions being distinguished by the terms "outboard aileron" and "inboard aileron".

An undesirable side effect of aileron operation is detrimental yaw - a yaw moment in the opposite direction of the roll. Using the ailerons to roll an airplane to the right creates a yaw motion to the left. As the aircraft rolls, adverse yaw is caused in part by the change in drag between the left and right wings. The rising wing creates increased lift, which causes increased induced drag. The descending wing creates decreased lift, causing decreased induced drag. The profile drag caused by the deflected ailerons can further increase the difference, along with changes in lift vectors as one turns back while the other turns forward.

A 1937 Waco VKS-7 cabin class biplane with four pairs of ailerons connected by an external vertical connector to simplify the aileron control system. So the ailerons on each side move together either up or down.

In a coordinated turn, the adverse yaw is effectively offset by the use of the rudder, resulting in a side force on the vertical stern that counteracts the adverse yaw by creating a beneficial yaw moment. Another method of compensation is "differential ailerons", which are mounted so that the downward aileron deflects less than the upward aileron. In this case, the opposite yaw moment is created by a difference in profile drag between the left and right wing tips. Frize ailerons reinforce this profile drag imbalance by protruding under the wing of an upwardly deflected aileron, most often by hinging them slightly behind the leading edge and near the bottom of the surface, with the lower part of the leading edge of the aileron surface protruding slightly below the underside of the wing if the aileron is deflected upwards, the profile drag on that side increases significantly. Ailerons can also be designed to use a combination of these methods.

When the ailerons are in the neutral position, the wing on the outside of the turn will develop more lift than the opposite wing due to the difference in airspeed across the wingspan, causing the aircraft to continue to roll. Once the desired bank angle (degree of rotation around the longitudinal axis) has been achieved, the pilot uses an opposite aileron to prevent the bank angle from increasing due to this change in lift over the wingspan. This slight opposite use of the controls must be maintained throughout the lap. The pilot also uses a small amount of rudders in the same direction as the turn to counter adverse yaw and create a "coordinated" turn with the fuselage parallel to the flight path. A simple indicator on the instrument panel called the slip indicator, also known as the "ball", indicates when this coordination has been achieved.

Aileron components

Horns and aerodynamic counterweights

Aileron horn visible from the wing tip on the upper wing of a Fokker Dr. I.

The control forces can be extremely heavy, especially with larger or faster aircraft. Borrowing a discovery from boats that extend the area of ​​a control surface in front of the hinge reduces the required forces, which first appeared on ailerons during World War I, when ailerons were extended beyond the wing tip and horned in front of the hinge. Known as overhanging ailerons, the Fokker Dr.I and Fokker D.VII are perhaps the best-known examples. Later examples have balanced the counterweight with the wing to improve control and reduce drag. This is now seen less frequently due to the Frize-type aileron which has the same benefit.

Trim tabs

Trim tabs are small movable sections that resemble scaled-down ailerons that are on or near the trailing edge of the aileron. In most propeller-driven aircraft, the rotation of the propeller (s) induces an opposing roll motion due to Newton's third law of motion, since every action has an equal and opposite reaction. To relieve the pilot in one direction to create constant pressure on the stick, trim tabs (which causes fatigue) are provided, adjusted or closed trim , the pressure needed against unwanted movement. The tab itself deflects with respect 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 the cockpit so that different power settings or flight settings can be compensated for. Some large aircraft from the 1950s (including the Canadair Argus) used free-floating control surfaces that the pilot controlled only by moving the trim tabs. In this case, additional tabs were provided to optimize the controls for straight and level flight.


Additional 300-liter aircraft from below with bright, square spades roughly in the middle of the wing.

Spades are flat metal plates that are usually attached to the underside of the aileron in front of the aileron hinge with a lever arm. They reduce the force the pilot needs to deflect the aileron and are commonly seen in aerobatic aircraft. When the aileron deflects upward, the spade creates a downward aerodynamic force that tends to rotate the entire assembly to deflect the aileron further upward. The size of the spade (and its lever arm) determines how much force the pilot needs to exert to deflect the aileron. A spade works like a horn but is more efficient because of the longer moment arm.

Mass balance weights

Mass balancing of the ailerons with Frize hinge on a Messerschmitt Bf 110 "Focuser"

To increase the speed at which the control surface flapping (aeroelastic flapping) can pose a risk, the center of gravity of the control surface is shifted towards the hinge line for that surface. To achieve this, lead weights can be attached to the front of the aileron. On some aircraft, the aileron design may be too heavy to allow this system to operate without unduly increasing the aileron weight. In this case, the weight can be added to a lever arm to move the weight well in front of the aileron body. These counterweights are teardrop-shaped (to reduce drag), which makes them distinctly different from the spades, although both protrude forward and under the aileron. In addition to reducing the risk of flutter, mass balances also reduce the stick forces required to move the control surface during maneuvers.

Aileron fences

Some aileron designs, especially when attached to swept wings, include fences, such as wing fences, that are flush with their inboard surface to suppress some of the span component of the airflow that travels on the top of the wing and the laminar flow above tends to interfere with that Aileron when deflected down.

Types of ailerons

Single acting ailerons

These ailerons were used during the pre-war "pioneering era" of aviation and the early years of World War I, and each was controlled by a single cable that pulled the aileron up. When the aircraft was at rest, the ailerons hung straight down. This type of aileron was used on the 1909 Farman III biplane and the Short 166. An "inverted" version of this, using wing distortion, existed on the later version of the Santos-Dumont Demoiselle which only warped the wing tips "downwards". One of the disadvantages of this design was a greater tendency to yaw than with simple connected ailerons. In the 1930s, some light aircraft used single-acting controls, but used springs to return the ailerons to their neutral positions when the control stick was released.

Wing tip aileron

The Blériot VIII with wing tip ailerons was deflected in 1908 for an easy right bank.

In the very first airframe with the combination of "joystick / rudder bar" controls that led directly to the modern flight control system, the Blériot VIII, in 1908, some designs of earlier aircraft used "wing tip" ailerons in which the entire wing tip was rotated to achieve a roll control as a separate, swiveling roll control surface. The AEA June Bug used some form of this, both with the 1916 experimental German Fokker V.1 and the earlier versions of the Junkers J 7 all-duralumin metal demonstrator monoplane that used them - the J 7 led directly to the German Junkers DI fully duralumin metal fighter design from 1918, which had conventionally articulated ailerons. The main problem with this type of aileron is the dangerous tendency to stall when used aggressively, especially if the aircraft is already threatened with stalling, hence its use mainly in prototypes and their replacement in production aircraft with more conventional ailerons.

Frize ailerons

The engineer Leslie George Frize (1897-1979) of the Bristol Airplane Company developed an aileron shape that is pivoted about 25 to 30% of the chord line and near its underside [1] to reduce the stick forces when the aircraft was getting faster the 1930s. When the aileron is deflected upward (so its wing goes down), the leading edge of the aileron begins to protrude from under the underside of the wing into the airflow below the wing. The moment of the leading edge in the airflow helps move the trailing edge up, reducing the stick force. The downward moving aileron also adds energy to the boundary layer. The edge of the aileron directs airflow from the bottom of the wing to the top of the aileron, creating a lifting force that is added to the lift of the wing. This reduces the required deflection of the aileron. Both the 1930 Canadian fleet biplane, Model 2, and the popular 1938 US Piper J-3 Cub monoplane had the designed Frize ailerons and helped introduce them to a wide audience.

One claimed benefit of the Frize aileron is its ability to counteract adverse yaw. To do this, the leading edge of the aileron must be sharp or bluntly rounded, which gives the flipped aileron significant drag and helps offset the yaw force created by the other aileron that was turned down. This can lead to unpleasant, non-linear effects and / or potentially dangerous aerodynamic vibrations (flutter). An unfavorable yaw moment is essentially counteracted by the yaw stability of the aircraft and also by the use of a differential aileron movement.

Differential ailerons

By carefully designing the mechanical connections, the aileron can deflect more upward than the aileron downward (e.g. U.S. Patent 1,565,097). This will help reduce the likelihood of wing tip stall when making aileron deflections at high angles of attack. In addition, the resulting difference in drag reduces deleterious yaw (as also discussed above). The idea is that the loss of lift associated with the aileron does not incur any penalty while the increase in lift associated with the aileron is minimized. The rolling couple in the aircraft is always the difference in lift between the two wings. A designer at de Havilland invented a simple and practical connection, and his classic British de Havilland Tiger de Mot biplane became one of the most famous and earliest aircraft to use differential ailerons.

Roll control without ailerons

Wing distortion

On the earliest Pioneer-era aircraft, such as the Wright Flyer and the later Blériot XI and Etrich Taube from 1909, lateral control was effected by twisting the outboard portion of the wing to increase or decrease lift by changing the angle of attack . This had the disadvantage that the structure was loaded, the controls were heavily loaded and there was the risk that the side with the increased angle of attack would come to a standstill during a maneuver. By 1916, most designers had given up wing deformation in favor of ailerons. Researchers at NASA and elsewhere have looked at wing distortion again, but under new names. The NASA version is the X-53 Active Aeroelastic Wing, while the United States Air Force has tested the Adaptive Compliant Wing.

Differential spoiler

Spoilers are devices that, when drawn into the airflow via a wing, disrupt the airflow and reduce the lift generated. Many modern aircraft designs, especially jet planes, use spoilers in place of or in addition to ailerons, such as the F4 Phantom II and Northrop P-61 Black Widow, which had almost full-width flaps (there were very small conventional ailerons on the wing tips, too).

Roll induced by oar

All aircraft with Dieder have a type of yaw-roll clutch to promote stability. Common trainers like the Cessna 152/172 series can only be roll steered with the rudder. The rudder of the Boeing 737 has more authority to roll over the aircraft than the ailerons at high angles of attack. This resulted in two notable accidents when the rudder jammed in the fully deflected position and caused rollover (see Problems with the Boeing 737 rudder).

Some aircraft like the Fokker Spin and Modellglider have no lateral control whatsoever. These planes consume more dihedral than conventional planes. The deflection of the rudder leads to yaw and a lot of differential wing lift, which creates a yaw-induced roll moment. This type of control system is most commonly used in the Flying Flea family of small aircraft and in simpler 2-function model gliders (pitch and yaw control) or 3-function models (pitch, yaw and throttle control) with model propulsion such as radio-controlled versions of "old timer" free-flight engines with engine propulsion.

Other methods

  • Weight shift control is widely used in hang gliders, powered hang gliders, and microlight aircraft.
  • The flight with disabled controls was successful in a small number of aircraft accidents.
  • Reaction control valves such as those used in the Harrier jump jet family of military aircraft.
  • Upper Rudder: This device was installed on the No. 1 aircraft of the British Army. It consisted of an omnidirectional fin mounted over the upper wing and pivoted around a vertical axis. During operation, it exerted a lateral force approximately above the center of pressure, which caused the vehicle to roll. The design also had all-flying ailerons between the wing planes, however these were removed at the time when the first official flight of a British aircraft was made and in-flight roll control was achieved solely through the use of the top rudder.

Combinations with other control surfaces

A USAF F-16 with its rear tailerons that move independently for both pitch and roll control. Note the different angles of attack that are visible.
  • A control surface that combines aileron and flap is called a Called flaperon . A single surface on each wing serves both purposes: as ailerons, the left and right flaperons are operated differently; When used as a flap, both flaperons are pressed downwards. When a flaperon is pressed down (ie used as a flap), there is enough freedom of movement to continue using the aileron function.
  • Some aircraft have spoilers or differentially controlled Used spoilerons to replace traditional ailerons Rolling movements provide. The advantage is that the entire trailing edge of the wing can be devoted to flaps, which allows better control at low speed. The Northrop P-61 Black Widow used spoilers in conjunction with full-span zap flaps in this manner, and some modern aircraft use spoilers to assist the ailerons.
  • On aircraft with delta wings, the ailerons become one with the elevators Elevon combined.
  • Some modern combat aircraft may not have ailerons on their wings, but they do offer roll control with a fully moving horizontal tail unit. When horizontal tail aircraft stabilizers can move differently to perform the roll control function of ailerons, as in some modern combat aircraft, they are referred to as "tailerons" or "rolling tails". Tailerons also allow wider flaps on the wings of the aircraft.
  • Aileron struts combined movable surfaces with an airfoil-shaped wing strut. Working in the slipstream of the propeller increased their effectiveness, although their mechanical advantage is reduced due to the position of the inboard.

See also





  • Bullmer, Joe. The WRight Story: The True Story of the Wright Brothers' Contribution to Early Aviation , CreateSpace Independent Publishing Platform, ISBN 1439236208, ISBN 978-1439236208, 2009.
  • Casey, Louis S. Curtiss, The Hammondsport Era, 1907–1915 , New York: Crown Publishers, 1981, pp. 12-15, ISBN 0-517543-26-5, ISBN 978-0-517543-26-9.
  • Parkin, John H. Bell and Baldwin: Their Development of Airfields and Hydrodromes in Baddeck, Nova Scotia , Toronto: University of Toronto Press, 1964.

External links

Search Wiktionary, the free dictionary Ailerons .