Figure 1-57.  Elevons.  Figure 1-58.  A stabilizer and index marks on a transport category  aircraft. Figure 1-59.  Ruddervator.  Figure 1-60.  Flaperons. Each contains a movable ruddervator built into the trailing  edge. Movement of the ruddervators can alter the movement  of the aircraft around the horizontal and/or vertical axis.  Additionally, some aircraft are equipped with flaperons.  [Figure 1-60]  Flaperons are ailerons which can also act as  flaps. Flaps are secondary control surfaces on most wings,  discussed in the next section of this chapter. There are several secondary or auxiliary flight control  surfaces. Their names, locations, and functions of those for  most large aircraft are listed in  Figure 1-61 . Flaps are found on most aircraft. They are usually inboard on  the wings’ trailing edges adjacent to the fuselage. Leading  edge flaps are also common. They extend forward and down  from the inboard wing leading edge. The flaps are lowered  to increase the camber of the wings and provide greater lift  and control at slow speeds. They enable landing at slower  speeds and shorten the amount of runway required for takeoff  and landing. The amount that the flaps extend and the angle  they form with the wing can be selected from the cockpit.  Typically, flaps can extend up to 45–50°.  Figure 1-62  shows  various aircraft with flaps in the extended position. Flaps are usually constructed of materials and with techniques  used on the other airfoils and control surfaces of a particular  aircraft. Aluminum skin and structure flaps are the norm on  light aircraft. Heavy and high-performance aircraft flaps  may also be aluminum, but the use of composite structures  is also common.  stabilizer and the elevator.  [Figure 1-58]  Basically, a  stabilator is a horizontal stabilizer that can also be rotated  about the horizontal axis to affect the pitch of the aircraft. A ruddervator combines the action of the rudder and elevator.  [Figure 1-59]  This is possible on aircraft with V–tail  empennages where the traditional horizontal and vertical  stabilizers do not exist. Instead, two stabilizers angle upward  and outward from the aft fuselage in a “V” configuration.  There are various kinds of flaps. Plain flaps form the trailing  edge of the wing when the flap is in the retracted position.  [Figure 1-63A]  The airflow over the wing continues over the  upper and lower surfaces of the flap, making the trailing edge  1-28 Elevons Secondary or Auxiliary Control Surfaces  Flaps Flaperons Ruddervator