LANDING GEAR

Figure 1-10.—Typical landing gear system. consequently reduced, and considerable drag is added to the wing. Another type of spoiler in common use is a long, slender, curved and perforated baffle that is raised edgewise through the upper surface of the wing forward of the aileron. It also disrupts the flow of air over the airfoil and destroys lift. These spoilers are actuated through the same linkage that actuates the ailerons. This arrangement makes movement of the spoiler dependent upon movement of the aileron. The linkage to the aileron is devised so that the spoiler is extended only when the aileron is raised. In other words, when the aileron moves downward, no deflection of the spoiler takes place. SPEED BRAKES.—Speed brakes are hinged, movable control surfaces used for reducing the speed of aircraft. Some manufacturers refer to them as dive brakes or dive flaps. They are hinged to the sides or bottom of the fuselage or to the wings. Regardless of their location, speed brakes serve the same purpose on all aircraft. Their primary purpose is to keep aircraft from building up excessive speed during dives. They are also used in slowing down the speed of the aircraft prior to landing. Speed brakes are operated hydraulically or electrically. SLATS. -Slats are movable control surfaces attached to the leading edge of the wing. When the slat is retracted, it forms the leading edge of the wing. At low airspeed, the slat improves the lateral control-handling characteristics and allows the aircraft to be controlled at airspeeds below the normal landing speed. When the slat is opened (extended forward), a slot is created between the slat and the leading edge of the wing. The slot allows high-energy air to be introduced into the air layer moving over the top of the wing. This is known as boundary layer control. Boundary layer control is primarily used during operations from carriers; that is, for catapult takeoffs and arrested landings. Boundary layer control can also be accomplished by a method of directing high-pressure engine bleed air through a series of narrow orifices located just forward of the wing flap leading edge. AILERON DROOP.—The ailerons are also sometimes used to supplement the flaps. This is called an aileron droop feature. When the flaps are lowered, both ailerons can be partially deflected downward into the airstream. The partial deflection aIlows them to act as flaps as well as to serve the function of ailerons. LANDING GEAR The landing gear of the earliest aircraft consisted merely of protective skids attached to the lower surfaces of the wings and fuselage. As aircraft developed, skids became impractical and were replaced by a pair of wheels placed side by side ahead of the center of gravity with a tail skid supporting the aft section of the aircraft. The tail skid was later replaced by a swiveling tail wheel. This arrangement was standard on all land-based aircraft for so many years that it became known as the conventional landing gear. As the speed of aircraft increased, the elimination of drag became increasingly important. This led to the development of retractable landing gear. Just before World War II, aircraft were designed with the main landing gear located behind the center of gravity and an auxiliary gear under the nose of the fuselage. This became known as the tricycle landing gear. See figure 1-10. It was a big improvement over the 1-11