A rotorhead is a helicopter component that houses the main rotors of the aircraft. The rotorhead consists of a swash plate, pitch change rod, rotor hub or spindle, vibration dampner, and rotor blades. These parts make up the large, spinning mass that sits on top of a helicopter.
The swash plate is a large, metal disc that connects the pilot’s controls to the rotorhead. Cyclic and collective mechanisms controlled by the pilot connect to the rotorhead via the swash plate. The swash plate actually rotates with the rotorhead, but the cyclic and collective mechanisms do not.
Pitch change rods connect the swash plate to the spindle or rotor hub. The function of pitch change rods is to alter the angles of the blades during rotation according to changes in the pilot’s controls. When looking at the rotorhead, pitch change rods will be aligned vertically while most other components are horizontal.
The blade is bolted to the rotor hub or spindle; the pitch change rod is also attached to this component. The hub not only rotates with the rotorhead but also rotates on its axis, hence the term “spindle.” The spindles translate input from the pilot’s controls to the blades via collective and cyclic mechanisms, swash plate, and pitch change rods.
The vibration damper is normally a mechanical, hydraulic, and pneumatic component that absorbs both mechanical and harmonic vibrations. Though very small, without vibration dampers, the rotorhead would probably fail due to metal fatigue. Vibrational dampers vary a great deal in size and design among helicopters.
Rotor blades are rotating wings. Since helicopters don’t have wings, the rotating blades are the wings. The profile of a rotor blade resembles a wing on an airplane. The rotor blades can be considered the most important part of the rotorhead, because they have the wing-shape design that enables an aircraft to fly. One interesting fact on any aircraft is that no propeller blade tip can exceed the speed of sound.
The entire rotorhead assembly is attached to a main gearbox or transmission via gears. Every part of the piece, minus the collective and cyclic mechanism, spins as one single unit. The rotorhead is a very busy unit and must be finely adjusted to achieve flight. It may appear that the blades of a helicopter are spinning like a house fan, but the truth is the blades must constantly change pitch and angle to maintain flight.