Flight Control Surfaces

The flight control surfaces are movable airfoils designed to change the attitude of the acft during flt. These surs may be divided into three groups usually referred to as the primary group, secondary group and auxiliary group.

The primary gp includes the ailerons, elevators and rudder. The ailerons are attached to the trailing edge of the wings and control the rolling motion of the acft. The elevators, attached to the horizontal stabilizer, control the climb or descent (pitching motion). The rudder, attached to the vert stblz, determines the horiz dir of flt (yawing motion).

The ailerons and elevators are generally operated from the cockpit by a control stick or by wheel and yoke assembly. The rudder is operated by foot pedals.

Рис. 4. Principal maneuvers of the aircraft:

1 - pitching motion -движение тангажа; 2 - lateral axis -поперечная ось; 3 - yawing motion -движение рыскания; 4 - vertical axis- вертикальная ось; 5 - longitudinal axis- продольная ось; 6 - rolling motion -движение крена

Included in the secd gp are the trim tabs and spring tabs. Trim tabs are small airfoils recessed into the trailing edges of the prim con surs. The purpose of trim tabs is to enable the pilot to trim out any unbalanced condition which may exist during flight, without exerting any pressure on the prim controls. Each trim tab is hinged to its parent prim con sur, but operated by an independent control. The purpose of spring tabs is to aid the plt in moving the prim con surs.

Included in the auxiliary gp of flt con surs are the wing flaps, spoilers, speed brakes and slats.

Wing flaps are used to give the acft extra lift and are hinged to the trailing or leading edge of the wing.

Spoilers are for the purpose of decreasing wing lift. They are long narrow surs, hinged at their leading edges to the upper sur of the wings.

Speed brakes are hinged surs used for slowing down the speed of an acft and attached to the wings. On some acft they are hinged to the lower sur of the fus.

Slats are movable control surs attached to the leading edges of the wings. When the slat is extended forward, a slot is created between the slat and the leading edge. At low airspeeds this increases lift and improves handling chars.