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

Figure 1-11.-Main landing gear.

conventional type. The tricycle gear is more stable during ground operations and makes landing easier, especially in crosswinds. It also maintains the fuselage in a level position that increases the pilots visibility. Nearly all Navy aircraft are equipped with tricycle landing gear.