Why Dampers Are Important in Helicopter Rotor Shafts
The rotor shaft of a helicopter is a center of activity, which is all carefully considered and accounted for during flight. Unlike airfoils on fixed wing aircraft, the propellers on helicopters move back, forth, up, and down during operation. With all this movement, it is important that the propeller movement is controlled. Various pieces of hardware such as bearings, fasteners, and dampers all help to stabilize the propeller movement. This blog will focus on the importance of dampers.
To begin, dampers are devices that are designed to prevent any resonance issues. Found in the lead/drag hinge, the dampers effectively absorb movement and therefore lessen the side effects of the rotational movement of the propellers on the helicopter’s center of gravity.
The lead/lag movement of propellers refers to the back and forth movement of the helicopter’s propellers. As the rotor spins, each blade responds to inputs from the control system to enable aircraft control. The propellers begin to flap upwards as the lift on a blade increases. In turn, the helicopter’s center of gravity shifts as a result of the individual movement of each propeller. Change in movement is usually a cause and effect chain. In this instance, the change in the center of gravity alters the speed of the whole Dampers rotor system. The lead/lag motion therefore needs to be regulated to ensure that the pilot has enough control over the rotor system. This is particularly important during moments when the flapping force of the propellers is stronger as a result of a maneuver.
Dampers are manufactured in various shapes and use various ways to absorb pressure. Hydraulic dampers for example, include a pressure pipe, piston rod, and the dampening medium of oil. The most common type of damper that is used in the rotor shaft are elastomeric or visco-elastic. Cylindrical in shape, elastomeric dampers are composed of two outer metal plates that sandwich together smaller metal plate, each separated by elastomeric layers such as molded silicone. The addition of elastomeric material is vital as the material has a high load strength and high tear rating. Under the stress of the propeller’s motion, the damper’s form stays intact.