Helicopter Hinges


The rotor blades in a fully articulate blade system are attached to the rotor hub through a series of hinges so that it can move in three ways and each blade can move independently of the other. The blades can move up and down, back and forth in the horizontal plane, and can change in the pitch angle (the tilt of the blade).

The hinges present in the articulate blade system are:

  • Flapping Hinge/Horizontal hinge
  • Lead-lag hinge/Drag hinge/Vertical hinge
  • Feathering Hinge/Pitch change hinge

Flapping hinges

The flapping hinges are horizontal hinges of a helicopter rotor that allow the blades to move up and down. This up and down motion of blades is called flapping.

The flapping motion created by flapping hinges can compensate for the dissymmetry of lift. For this purpose, the flapping hinges may be located at varying distances from the rotor hub. When a blade is on the advancing side, its increased lift causes the blade to flap upwards, which effectively reduces its incidence. The opposite occurs on the retreating side. The use of flapping hinges creates better force balance on the rotor, distributing lift more evenly. The flapping motion caused by these hinges makes bending forces and rolling moments less effective on the helicopter body. Centrifugal force is typically enough to prevent the blades from flapping to a large degree, but many helicopters also employ stops as an added preventive measure.

Drag hinges

The drag hinges are vertical hinges of a helicopter rotor that allow the blade to move back and forth. This back-and-forth motion of blades is called drag hinges.

Dampers are usually used to prevent excess back and forth movement around the drag hinge. The purpose of the drag hinge and dampers is to compensate for acceleration and deceleration caused by the difference in drag experienced by the advancing and retreating blades.

Feathering hinges

The third hinge in the fully articulated system is called the feathering hinge about the feathering axis. This hinge is responsible for the change in pitch of rotor blades excited via pilot input to the collective or cyclic. Although the total rotor thrust remains the same, cyclic feathering creates differential lift across the rotor disc.  The pilot uses this differential lift to control the helicopter’s attitude. This is possible due to the pitch hinge.




The following project shows the different kinds of hinges in a helicopter rotor blade. The different phenomena can be experienced with a click of a button.

This project can also be viewed on mobile.

Helicopter Hinges on Scratch


This project shows the 3 different kinds of hinges. 

Just click the buttons to see the Flap, Pitch, and Lead-Lag Hinge.







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