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A helicopter with two screws
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A helicopter with two screws

A helicopter with two screws

 

Among the large number of helicopter schemes developed so far, a scheme with two coaxially located rotors is widely used, which was first used by MV Lomonosov on his "aerodrome machine". Both rotors in this circuit are on the same axis, one under the other. The shaft of the upper screw thus passes inside the hollow shaft of the lower screw. The screws rotate in opposite directions, therefore two reactive moments are transmitted to the fuselage, mutually balancing each other. Helicopters built according to this scheme have good maneuverability.

In particular, by changing the angles of the blades of one of the screws in comparison with mounting angles of the blades of another propeller (differential change in the overall pitch propellers) achieved by the difference in their reaction torque, which is being transferred to the fuselage, the helicopter rotates in one direction or another. The longitudinal and lateral control and management of the rise and descent will be described below. Now, we note only that the principles of such management are the same for most helicopters.

 

A helicopter with two screws 2

A helicopter with two screws

 

The Russian helicopter has been built under this scheme is still in 1907, the designer of the Antonov. Subsequently, the scheme used in many countries. Modern helicopter design II. I. Kamov also designed for twin-screw coaxial scheme.

The main advantages of helicopters, built under this scheme are its small size and light weight. This is achieved by the absence of the long tail boom to the tail rotor installation n long shafts to transmit torque from the motor to the screw, as the screws are mounted on a vertical axis next mail.

It is interesting to note that all helicopters weighing up to 800 kg built on the twin-screw coaxial scheme. It is possible that the helicopters will be in the near future, widespread use of individual aircraft.

This scheme, like any other, is not without drawbacks. Thus, due to the fact that the lower screw runs in a stream of air, thrown and twisted the upper screw, deteriorating conditions of work and difficult calculation in the design of the screw.

Helicopter with two longitudinally spaced rotors

Driving a helicopter with a longitudinally arranged rotors was first proposed NI Sorokin. According to this scheme, one screw located above the forward fuselage, and the second - on the tail. Both screws can be driven into rotation by one or two motors. Screw rotational direction opposite to the mutual settlement of reactive moments.

 

Helicopter rotors with two

Helicopter rotors with two

 

Under this scheme, it is advantageous to build a heavy multi-seat helicopter, since the fuselage of such a helicopter is a convenient place for cargo and passengers, and in addition, the helicopter of this scheme has good longitudinal controllability and allows a significant change in the position of the center of gravity along the axis of the fuselage. So, if the helicopter will lower its nose, that is, the center of gravity has moved forward, a dive moment will be created which can easily be eliminated by increasing the thrust of the nose screw with a corresponding reduction in the propeller thrust installed in the tail. When moving the center of gravity of the groove, we must increase the thrust of the screw installed in the tail, and reduce the thrust of the nose screw.

Advantage helicopter constructed according to this scheme is that it has a small cross-section of the fuselage, and therefore, low resistance to harmful, allowing fly with the greatest speed.

 

Helicopter rotors with two

 

Lack helicopter constructed according to this scheme is that the screw at the rear of the helicopter forward flight running in the air pre-perturbed forward screw, which reduces its efficiency.

Shown model helicopter with two longitudinally extending screws. Rotor blades for easier storage hangar can be made folding above the fuselage, which greatly reduces the size of the helicopter.

 

A helicopter with two rotors 23

Helicopter rotors with two

 

 

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