Editing Flight control surfaces (section)

==Main control surfaces==
The main control surfaces of a [[fixed-wing aircraft]] are attached to the airframe on hinges or tracks so they may move and thus deflect the air stream passing over them.  This redirection of the air stream generates an unbalanced force to rotate the plane about the associated axis.
[[File:Boeing 727 flight control surfaces.svg|thumb|700px|center|Flight control surfaces of Boeing 727]]

===Ailerons===
{{main|Aileron}}
[[File:Alieron A-44 (PSF).png|thumb|right|Aileron surface]]
[[Ailerons]]  are mounted on the trailing edge of each wing near the wingtips and move in opposite directions. When the pilot moves the [[Aircraft flight control system|aileron control]] to the left, or turns the wheel counter-clockwise, the left aileron goes up and the right aileron goes down. A raised aileron reduces lift on that wing and a lowered one increases lift, so moving the aileron control in this way causes the left wing to drop and the right wing to rise. This causes the aircraft to roll to the left and begin to turn to the left. Centering the control returns the ailerons to the neutral position, maintaining the [[Banked turn#Aviation|bank angle]]. The aircraft will continue to turn until opposite aileron motion returns the bank angle to zero to fly straight.

===Elevator===
{{main|Elevator (aircraft)}}

The [[Elevator (aircraft)|elevator]] is a moveable part of the [[horizontal stabilizer]], hinged to the back of the fixed part of the horizontal tail. The elevators move up and down together. When the pilot pulls the stick backward, the elevators go up. Pushing the stick forward causes the elevators to go down.  Raised elevators push down on the tail and cause the nose to pitch up. This makes the wings fly at a higher [[angle of attack]], which generates more lift and more [[drag (physics)|drag]].  Centering the stick returns the elevators to neutral and stops the change of pitch.  Some aircraft, such as an [[MD-80]], use a [[servo tab]] within the elevator surface to aerodynamically move the main surface into position.  The direction of travel of the control tab will thus be in a direction opposite to the main control surface.  It is for this reason that an [[MD-80]] tail looks like it has a 'split' elevator system.

In the [[canard (aeronautics)|canard arrangement]], the elevators are hinged to the rear of a foreplane and move in the opposite sense, for example when the pilot pulls the stick back the elevators go down to increase the lift at the front and lift the nose up.

===Rudder===
{{main|Rudder#Aircraft rudders}}

The [[rudder]] is typically mounted on the trailing edge of the [[vertical stabilizer]], part of the [[empennage]]. When the pilot pushes the left pedal, the rudder deflects left.  Pushing the right pedal causes the rudder to deflect right.  Deflecting the rudder right pushes the tail left and causes the nose to yaw to the right. Centering the rudder pedals returns the rudder to neutral and stops the yaw.

===Secondary effects of controls===

====Ailerons====
{{Main|Adverse yaw}}
The ailerons primarily cause roll. Whenever lift is increased, [[induced drag]] is also increased so when the aileron control is moved to roll the aircraft to the left, the right aileron is lowered which increases lift on the right wing and therefore increases induced drag on the right wing. Using ailerons causes [[adverse yaw]], meaning the nose of the aircraft yaws in a direction opposite to the aileron application. When moving the aileron control to bank the wings to the left, adverse yaw moves the nose of the aircraft to the ''right''. Adverse yaw is most pronounced in low-speed aircraft with long wings, such as gliders. It is counteracted by the pilot using the rudder pedals. [[Differential ailerons]] are ailerons which have been rigged such that the downgoing aileron deflects less than the upward-moving one, causing less adverse yaw.

====Rudder====
The rudder is a fundamental control surface which is typically controlled by pedals rather than at the stick. It is the primary means of controlling yaw—the rotation of an airplane about its vertical axis. The rudder may also be called upon to counter-act the adverse yaw produced by the roll-control surfaces.

If rudder is continuously applied in level flight the aircraft will yaw initially in the direction of the applied rudder – the primary effect of rudder. After a few seconds the aircraft will tend to bank in the direction of yaw. This arises initially from the increased speed of the wing opposite to the direction of yaw and the reduced speed of the other wing. The faster wing generates more lift and so rises, while the other wing tends to go down because of generating less lift. Continued application of rudder sustains rolling tendency because the aircraft flying at an angle to the airflow - skidding towards the forward wing. When applying right rudder in an aircraft with [[Dihedral (aircraft)|dihedral]] the left hand wing will have increased angle of attack and the right hand wing will have decreased angle of attack which will result in a roll to the right. An aircraft with [[Dihedral (aircraft)#Anhedral|anhedral]] will show the opposite effect.
This effect of the rudder is commonly used in model aircraft where if sufficient dihedral or polyhedral is included in the wing design, primary roll control such as ailerons may be omitted altogether.

===Turning the aircraft===
{{Main|Banked turn#Banked turn in aeronautics}}
Unlike turning a boat, changing the direction of an aircraft normally must be done with the ailerons rather than the rudder. The rudder turns (yaws) the aircraft but has little effect on its direction of travel. With aircraft, the change in direction is caused by the horizontal component of lift, acting on the wings. The pilot tilts the lift force, which is perpendicular to the wings, in the direction of the intended turn by rolling the aircraft into the turn. As the bank angle is increased, the lifting force can be split into two components: one acting vertically and one acting horizontally.

If the total lift is kept constant, the vertical component of lift will decrease. As the weight of the aircraft is unchanged, this would result in the aircraft descending if not countered. To maintain level flight requires increased positive (up) elevator to increase the angle of attack, increase the total lift generated and keep the vertical component of lift equal with the weight of the aircraft. This cannot continue indefinitely. The total [[Load factor (aeronautics)|load factor]] required to maintain level flight is [[Banked turn#Aviation|directly related to the bank angle]]. This means that for a given airspeed, level flight can only be maintained up to a certain given angle of bank. Beyond this angle of bank, the aircraft will suffer an accelerated [[stall (flight)|stall]] if the pilot attempts to generate enough lift to maintain level flight.

===Alternate main control surfaces===

Some aircraft configurations have non-standard primary controls. For example, instead of elevators at the back of the stabilizers, the [[stabilator|entire tailplane may change angle]]. Some aircraft have a [[V-tail|tail in the shape of a V]], and the moving parts at the back of those combine the functions of elevators and rudder. [[Delta wing]] aircraft may have "[[elevon]]s" at the back of the wing, which combine the functions of elevators and ailerons.