Each main landing gear is composed of a shock strut assembly, dual wheels, a retracting cylinder, an uplock cylinder, and upper and lower drag braces. The wheels retract into a well, recessed into the underside of the sponsons. The dual wheels, equipped with tubeless tires and hydraulic brakes, are mounted on axles. They are part of the lower end of the shock strut piston. The main landing gear is extended hydraulically. In case of hydraulic failure, an emergency system of compressed air lowers the gear. Should the air system fail, the pilot actuates a valve to allow the gear to fall by its own weight.

Retractable landing gear is not a feature common to all helicopters or even a majority of them. The H-3 is discussed here because it is one of the Navys latest helicopter designs. The H-3 has emergency water-operational capability.

The H-3 tail landing gear is nonretracting and full swiveling. It serves as an aft touchdown point for ship/land-based operations only. An air-oil type of shock absorber cushions the landing shock.

The main rotor (rotary wing) and the rotor head are discussed under the rotor head section because their functions are closely related. Neither has a function without the other.

The main rotor or rotary wing on the H-3 has five identical wing blades. Other helicopters may have two, three, or four blades. A typical wing blade is shown in figure 1-17.

The rotary-wing blade is made of aluminum alloy, except the steel cuff by which the blade attaches to the rotor hub. The main supporting member of the blade is a hollow, aluminum alloy extruded spar, which forms the leading edge. The steel cuff is bolted to the root end of the spar.

Twenty-three individual pockets constructed of aluminum ribs, aluminum channels, and aluminum skin covering are bonded to the aft edge of the spar. The tip end of the blade contains a readily removable tip cap. Screws fasten the spar and tip pocket rib together. The root pocket of the blade is sealed at its inboard end by an aluminum alloy root cap that is cemented and riveted to the pocket.

A stainless steel spar abrasion strip is found at the leading edge of the spar. It starts at blade pocket No. 10 and extends along the entire leading edge, which includes the tip cap. The blade shown in figure 1-17 is fitted with a ice guard. The guard is composed of fine wire braid heating elements. It is interwoven in bands and embedded in a rubber strap, to which is bonded a stainless steel strap. The guard is bonded to the leading edge of the spar, and is molded to the contour of the blade.

The rotary-wing head is splined to and supported by the rotary-wing shaft of the main gearbox. The head supports the rotary-wing blades. It is rotated by torque from the main gearbox, and transmits movements of the flight controls to the blades.

The principal components of the head are the hub and swashplate. The hub consists of a hub plate and lower plate. It has hinges between each arm of the plates and sleeve-spindles, which are attached to the hinges. There is also a damper-positioner for each wing blade. The swashplate consists of a rotating swashplate and stationary swashplate. Other components of the rotary- wing head are anti flapping restrainers, droop restrainers, adjustable pitch control rods, and rotating and stationary scissors.

The swashplate and adjustable pitch control rods permit movement of the flight controls to be transmitted to the rotary-wing blades. The hinges allow limited movement of the blades in relation to the hub. These movements are known as lead, lag, and flap. Lead occurs during slowing of the drive mechanism when the blades have a tendency to remain in motion. Lag is the opposite of lead, and occurs during acceleration when the blade has been at rest and tends to remain at rest.

Flap is the tendency of the blade to rise with high-lift demands as it tries to screw itself upward into the air. The damper-positioners restrict lead and lag motion and position the blades for folding. Sleeve-spindles allow each blade to be rotated on its spanwise axis to change the blade pitch. The antiflapping restrainers and droop restrainers restrict flapping motion when the rotary-wing head is slowing or stopped.