Arrangements of helicopter rotors. There are five main configurations:
i. Single main rotor/tail rotor. In this arrangement, a main rotor provides vertical thrust and helicopter control while a small tail rotor fitted at the tail end of fuselage provides the yaw control.
ii. Tandem. In this configuration, two rotors located at each end of the fuselage are aligned in a longitudinal direction. The rear rotor sits higher than the main rotor.
iii. Side-by-side. In this arrangement, the main rotors are placed in a lateral sense on the pylons (i.e., perpendicular to the tandem). Both experience similar aerodynamic forces in forward flight.
iv. Coaxial. In this arrangement, two main rotors are on the same axle. This configuration is more common on rotorcraft used on board ships.
v. Synchropter. This configuration has two axles very close together and inclined outward. It is similar to the coaxial but the rotors are at the same height, making it a more compact arrangement.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved