The different types of helicopters configurations

However throughout history there have been 4 different types of helicopters that are commonplace:

• Single main rotor with a tail rotor – or any other type of tail mechanism.
• Tandem rotors such as the Boeing Chinook
• Coaxial rotors which are two rotors mounted on the same axis, but turning in different directions. This configuration is especially common among Russian military helicopters
• Intermesing rotor configuration, which consists of two rotors placed on separate axises, that are placed very close to each other. The rotors move in opposite direction – and at the same speed – so that they do not hit each other.

Single main rotor with a tail rotor
Single rotor helicopters must have a mechanism to neutralize the yawing movement created by the single large rotor. This is what the tail is required for.

The tail rotor is a smaller rotor mounted so that it rotates vertically or close- vertically at the end of the tail of a conventional single-rotor helicopter. The location and distance from the center of gravity of the tail rotor allow it to develop push in the exact same direction as the main rotor’s rotation, to counter the torque effect created by the main rotor. Tail rotors are simpler than main rotors since they need thrust to vary. The pitch of the tail rotor blades is adjustable by the pilot via the anti-torque pedals, which also provide directional control by allowing the pilot to rotate the helicopter around its vertical axis.

Tandem rotors
Tandem rotor helicopters have two large flat rotor assemblies. Currently this configuration is largely used for big cargo helicopters. Tandem rotor helicopters have the advantage of having the ability to hold more weight with shorter blades, since there are two sets. Tandem rotor helicopters usually require less power to hover and realize low rate flight as compared to single rotor helicopters.

Coaxial rotors
Coaxial rotors are a pair of rotors turning in opposite directions and mounted one above the other on the exact same shaft. The upside of the coaxial rotor is that, in forward flight, the lift provided by each rotor compensates for the retreating lift of the other rotor. This makes them efficient and good at lifting heavy cargo.

Intermeshing rotors
Intermeshing rotors have high stability and strong lifting capacity. This configuration is sometimes referred to as a synchropter. Most intermeshing layouts have two blades per mast, although exceptions such as with three blades per mast do exist.