Aileron

Aileron ( english: Aileron ) provide almost all 3-axis controlled aircraft for flight control about the longitudinal axis.

Ailerons are generally flaps on the wing trailing edge, which are moved simultaneously and in opposite directions. Aileron, which is moved downwards, the lift on its side is increased, thereby cancels the airfoil. The other aileron moves up, thus decreasing the lift, and the wing is lowered. Such a rolling movement is produced about the longitudinal axis.

Development and history

For the first time a functioning and well-known aileron was designed and tested, as it is still used today in aviation by the Frenchman Robert Esnault - Pelterie. Earlier in the 19th century dealt already theoretically Clément Ader, Charles Renard, Edson Gallaudet, Alphonse Pénaud and John Joseph Montgomery with the possibility and the construction of an aileron

The adverse yaw

An adverse secondary effect of the aileron insert ( also called aileron yaw moment ) arises from the fact that the decisive end of each upward aileron accelerates the wings ( the air resistance is reduced ), but the moved down the wing brakes (resistance increases ): the travel of the down aileron, which raises a wing causes in addition to the increased lift on this side of the aircraft at the same time an excessive air resistance, which in turn causes a significant braking effect on this ( outside curve ) side. Consequently, the plane in addition to the intended giert rolling movement, but to the opposite side (negative). For this reason, the operation of the aileron to a negative yaw leads (ie: moving the aircraft nose against the deliberate control direction ), so clean curves on the plane coordinated with aileron and rudder ( in the direction of the curve to compensate for adverse yaw torque ) must be flown. Larger aircraft usually have a so-called yaw damper (English yaw damper ), which automatically adjusts the rudder deflection for various flight conditions; a conscious help steer the rudder by the pilot is unnecessary in this case. In addition, we distinguish these aircraft between low - and high-speed ailerons, cf wing.

The adverse yaw can be mitigated by the construction of the aircraft or eliminated when the engine airplanes. A mechanically simple to implement way of weakening is the differential control, in which the moving down aileron deflects less far than the other. You can eliminate the adverse yaw during engine aircraft, increased in the top of the trailing edge of the aileron a vertically standing metal strip resistance of the rudder at the upward deflection considerably. A positive application of the adverse yaw is the sideslip.

The aileron trim is done by so-called trim tab.

Furthermore, it should be noted that less buoyancy caused a wing in an inclined position ( vertically upward acting force ), because its air force ( " lift " at right angles to the wing ) vectorially divided down in the lift and a pushing force for the suspended part of the wing. Therefore, the elevator must be actuated when ailerons used easily, resulting in increased angle of attack and resistance and slows down the aircraft. For gliders, this means that they so need to build speed before turning flight by sink that in the curve not the stall speed is reached.

Wing twist

In the early days of aviation, the roll control was often achieved without ailerons, but by wing warping. The ends of the wings were twisted cable pulls something, which also revealed a difference in lift between the two wings and thus rolling the aircraft.

The Wright brothers, whose aircraft were controlled by wing warping, were of the opinion that their broad approach patent also covered Glenn Hammond Curtiss invented method of roll control through ailerons and processed so against Curtiss.

Ailerons were first used by Robert Esnault - Pelterie on a non-powered biplane glider in 1904. The wing warping used in addition to the Wright Flyer and other early airplanes, such as the Bleriot XI ( 1908), the Etrich dove and their replicas (1909 ), the morane -Saulnier N ( 1915) and the numerous variants of the Fokker monoplane (1915), as well as some gliders like the Harth- Messerschmitt S7 ( 1918).

Aileron reversal

When the aileron is operated, increases on that wing, wherein the aileron deflects downward by the increased geometric curvature of the profile skeleton line of the angle of attack. In addition, the downward decisive end in the higher pressure region ailerons also causes an increase in resistance.

In extreme slow flight, this can lead to one-sided flow separation at this wing, which he, rather than move up, down "falls". At the same time as a rotational movement about the vertical axis is caused by the increased resistance, this may cause the aircraft to spin. This effect is, technically known somewhat inaccurately, " aileron reversal".

Most modern aircraft have suitable constructional measures barely an aileron reversal.

Replacement of the aileron by opposing elevator

In many modern fighter aircraft the elevators assist the ailerons in that they are as ailerons move in opposite directions. When this tornado in opposite directions controllable elevator replaced the aileron entirely. This design is in the English technical term also Taileron ( combined aileron and tailplane ) called. The advantage of thus possible extremely large, almost the entire wing length continuous landing flaps (and thus high payload ) is bought by a slightly reduced roll rate. And thus very effective - - To this important characteristic of a combat aircraft to bring to the required high levels, the wings of the tornado relatively far outside were each equipped with a spoiler per wing. This reduced when extending unilaterally lift and thus generate the required high torque to the aircraft longitudinal axis, thereby supporting tailerons. This spoiler and all movable flaps and wings are driven by the tornado a sophisticated fly- by-wire flight control.