ULTRALIGHT COAXIAL HELICOPTER

The coaxial scheme of helicopter propellers is not often used in modern helicopter construction. However, it is interesting to know what explains the rarity of using coaxial propellers?

As you know, the most common scheme in the world is the one with a main rotor and an open tail rotor, which is intended to compensate for the reactive moment from the main rotor.  After all, it “spins” the helicopter in the direction opposite to the rotation of the main rotor.

The undoubted advantage of the steering scheme is its structural simplicity, relatively low maintenance and repair costs.  However, if the helicopter loses the tail rotor, it can lose control and fall.

The coaxial propeller scheme is less common, but its use makes the helicopter more tenacious and, accordingly, more suitable for performing aviation tasks.  Interestingly, the use of a coaxial scheme is the result of the work of Soviet designers. The first domestic helicopter with a coaxial scheme was introduced in 1948.  It was the Ka-8 Irkutyanin, produced by the Kamov Design Bureau in only three copies.  Then they released the Ka-10 and Ka-15.  The last helicopter was the first product of the Kamov Design Bureau to enter mass production.  Hence, in the Soviet Union began the serial production of helicopters with coaxial propellers. Unlike the classic single-screw scheme, it is much more difficult to implement a coaxial scheme in practice.  Experts call it one of the most outstanding achievements of the domestic helicopter industry.  However, the complexity in design and execution is offset by the undoubted advantages of the coaxial scheme.

Firstly, coaxial helicopters have smaller dimensions, high compactness, which increases the angular velocity and makes the machine more maneuverable.  In particular, such a helicopter is capable of performing “funnel”, “oblique loop” figures, which cannot be performed by helicopters with a tail rotor.

Secondly, coaxial helicopters have greater survivability due to the absence of a tail rotor with its gearbox and drives.  At the same time, it is easier for the helicopter to maneuver near the ground or other surface on which it can land.

Thirdly, coaxial helicopters have a higher weight load coefficient, that is, the ratio of payload and total flight mass. Such characteristics of coaxial helicopters determined the specifics of their application. Coaxial helicopters are more effective as carrier-based helicopters, it is possible to use them as an amphibian on floats, with the ability to take off/land on water and on earth, they can also be used in high mountainous areas with difficult meteorological conditions, which makes this coaxial helicopter unique in its class.