The Different Rotors (Helicopter)

The helicopter as an aircraft is not as simple as it seems, the unique flight features make the helicopter a feat of flight science. It is not just making it fly, it is making it controllable and safe. Well, this machine has a rotor system that was practically an engineering miracle.

When rotating the blades, this produces the famous lift since the blades have an airfoil similar to an airplane’s wings, then the helicopter can lift. However, problems arise, how to be stable? Here the smart science of the rotors comes.

Airfoil from a blade of the main rotor. Source: aviation.stackexchange.com

As many of us may notice, there are different types of rotor configurations. But the most known configuration, a simple main rotor and a tail rotor. The explanation:

A single main rotor requires overcoming the torque that is a turning force or twisting force, this makes a reaction on the fixed body (fuselage). That is why the single rotor configuration needs a tail rotor to solve this reaction on the fuselage.

Visible Torque when the tail rotor fails. Source: Helicopter Loses Tail Rotor and Crashes/TheBestFootballGools/Youtube.com

In the video you can see the loss of control of the helicopter without a tail rotor. There are several alternatives or different designs that overlook this approach. Instead of using a tail rotor, the helicopter is designed with a NOTAR system. The NOTAR (no tail rotor) produces the control and stability needed when flying, use the Coanda effect on the helicopter’s tail.  

NOTAR. Source: mdhelicopters.com
NOTAR explained. Source: JUSTHELICOPTERS/Youtube.com

Another type of helicopter configuration beyond the single rotor is the coaxial type. The coaxial rotor comprises two rotors in the same axle, rotating in the opposite direction, one above the other. And the torque (that makes the fuselage turns)? It is eliminated since the rotors rotate in opposite directions, therefore it does not require a tail rotor or anti-torque system.

Kamov Ka-52, a coaxial rotor helicopter. Source: besthqwallpapers.com
The ingeniuty is a coaxial rotor helicopter drone. Source: mars.nasa.gov

The intermeshing rotors, similar to the coaxial, but in a different shaft, with a slight angle to the other, and the blades intermesh without colliding.

Kaman K-max, a model with intermeshing rotors. Source: Sudipta Sadhukhan/Youtube.com

Finally, in the tandem configuration, these helicopters have two main rotors, and there is no need in using a tail rotor or anti-torque system. The rotors are counter-rotating, cancelling the torque of each other as made with the other technologies of rotors.

The Boeing CH-46 Sea Knight helicopter was in service with the US Marine Corps for 50 years. Source: military-today.com

Here, it was explained the different types of rotors and how the system is stabilized. For controlling this aircraft, the rotors need to changes the position as well as the blades. Depending on the system and the type of helicopter this is configured. It could be explained in another article soon.


References:

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook/media/hfh_ch01.pd

MDhelicopters.com

Cover photo:

Kaman.com

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