What Is a Helicopter?

An airplane by its nature wants to fly. A helicopter does not want to fly. It is maintained in the air by a variety of forces and controls working in opposition to each other, and if there is any disturbance in this delicate balance, the helicopter stops flying, immediately and disastrously. There is no such thing as a gliding helicopter. 

Harry Reasoner, 1971 interview

Main Rotor Head Assembly

Taping so the proseal can be applied between those two strips of tape.
Next, that seal is pushed close to the outer strip of tape.
Grease is applied to the XXX and then the grip is pushed on.
This pushes that seal up over the XXX and causes it to form a seal.

 

Applying the proseal

Excluder seal?

Applying grease to help grip go on and to help fight corrosion.

upside down

grip attached.
t-strap matches up with that hole at one end

Bolt goes through the hole to secure t-strap

You know it's on right because that notch lines up

notice the seal and beading

Fitting
Other end of the t-strap goes into this fitting

Pin goes into the fitting and secures the t-strap

Each part that makes up this component has a part number and a serial number.  A manifest is created to show all of the numbers, and a maintenance log is created for each part.  Original documentation for each part is saved and attached to the maintenance log in case verification is ever needed.  If this helicopter were to crash, the owner would need to know where all the parts were purchased.

https://science.howstuffworks.com/transport/flight/modern/helicopter5.htm

A helicopter's main rotor is the most important part of the vehicle. It provides the lift that allows the helicopter to fly, as well as the control that allows the helicopter to move laterally, make turns and change altitude. To handle all of these tasks, the rotor must first be incredibly strong. It must also be able to adjust the angle of the rotor blades with each revolution they make. The pilot communicates these adjustments through a device known as the swash plate assembly.

The swash plate assembly consists of two parts — the upper and lower swash plates. The upper swash plate connects to the mast, or rotor shaft, through special linkages. As the engine turns the rotor shaft, it also turns the upper swash plate and the rotor blade system. This system includes blade grips, which connect the blades to a hub. Control rods from the upper swash plate have a connection point on the blades, making it possible to transfer movements of the upper swash plate to the blades. And the hub mounts to the mast via the Jesus nut, so named because its failure is said to bring a pilot face-to-face with Jesus.

The lower swash plate is fixed and doesn't rotate. Ball bearings lie between the upper and lower swash plates, allowing the upper plate to spin freely on top of the lower plate. Control rods attached to the lower swash plate connect to the cyclic- and collective-pitch levers. When the pilot operates either of those two levers, his or her inputs are transmitted, via the control rods, to the lower swash plate and then, ultimately, to the upper swash plate.

Using this rotor design, a pilot can manipulate the swash plate assembly and control the helicopter's motion. With the cyclic, the swash plate assembly can change the angle of the blades individually as they revolve. This allows the helicopter to move in any direction around a 360-degree circle, including forward, backward, left and right. The collective allows the swash plate assembly to change the angle of all blades simultaneously. Doing this increases or decreases the lift that the main rotor supplies to the vehicle, allowing the helicopter to gain or lose altitude.