Flight initiation course

The helicopter has three different controls: the cyclic, which controls the tilt (left and right) and pitch (nose down and up), varying the plane of rotation of the main rotor; The collective, which controls the power (the angle of the main rotor blades) to raise and lower and the pedals, which control the rotation to the right and left varying the angle of the tail rotor blades. In addition, there is the command of the engine or motors, usually automatic, although some are manual.

So far, an effective system that allows the helicopter to be launched as it does from a fighter plane with an ejection seat has not been achieved. (The Kamov Ka-50 military helicopter has built-in this system). Actually, the parachute is the helicopter itself, and more specifically the main rotor.

Unfortunately, the helicopter can not plan, but "drop in". The maneuver called autorotation allows to land with the engine stopped or without power applied to the rotors due to the operation of a system similar to that of bicycles (when the pedal stops, the rear wheel keeps turning) called free wheel. This system allows the main rotor (and the tail rotor associated with it) to rotate in the same way as a windmill does because of the flow of air from the bottom up while the helicopter descends.

In order to enter autorotation, the collective control must be lowered completely and in a very short time (of the order of two seconds) otherwise the main rotor would stop due to the resistance of the air until it loses revolutions and could no longer Support the helicopter. Hence a saying of helicopteristas: "before the doubt, autorrotación".

Although the autorrotation allows to reach the ground with guarantees, it is an extremely difficult maneuver, since the rate of descent during the same approaches the 2000 ft./min. (About 600 m / min or 10 m / sec) and the indicated speed is maintained around about 650 KIAS (approximate conditions of R22).

If contact with the soil were made under these conditions, the result would be catastrophic. Therefore, at the end of the autorotation and very close to the ground (about 30 m.), A flare or aerodynamic braking is performed by rapidly climbing the nose of the helicopter until about 20 °. This achieves three things: a moderate increase of r.p.m. Of the rotor (and therefore of the lift), a large decrease of the indicated speed (ideal is 0 KIAS) and a large decrease of the rate of descent (below 500 ft./min.).

Once the braking is finished, the pilot lowers the nose until it is placed slightly above the horizon and applies the collective control to dampen the entrance to the ground by changing the rotor lift by descent regime (the higher the collective the slower the descent, Provided that the rotor rpm loss is within limits).

Training in autorotations should be continuous, especially in single-engine helicopters. In the basic course of helicopters these maneuvers are practiced with assiduity in the R22, entering autorrotation from 600 ft. On the ground and trying to enter a picture of about 15x15 m. Without breaking the helicopter!

It can not be said that one is more difficult to pilot than another, each one has its peculiarities. The helicopter requires a great coordination between the hands and the feet, and the movements of the controls generally have to be very small, reason why "fine hands" are needed.

Based on the fact that the helicopter was invented to cover the gap between the surface vehicle and the aircraft, no great speed is needed. The fundamental problem is the rotor of the helicopter, which at high speeds suffers a series of aerodynamic phenomena that limit its maximum speed. Even so, modern helicopters have acceptable speeds, allowing them to "rub shoulders" with conventional airplanes, and even with some fighters, on airport landings.

Theoretically yes, provided that the maneuvers are within the resistance limits of its components (rotor, structure). Even so, the maneuvers would not be as colorful as in conventional aircraft (for example, looping is much more like an ellipse than a circle) because of the aerodynamic problems inherent in the design of the helicopter.

No. Due to the aerodynamic problems that appear in the lateral and back flight, the speed in these cases is much lower than in the forward (about a quarter of this in "normal" helicopters and 50% in models of combat).

As far as the power plant is concerned, there are no major differences from a conventional blast engine or turbine / turboprop aircraft except that helicopter turbines do not have a post-burner. However, the rest of the components of the power train are much more complicated.

In multi-engine (usually twin-engine) helicopters, the main transmission box must be capable of absorbing, combining and transforming the power supplied by the motors (which do not always rotate at the same r.p.m. and therefore do not provide the same torque). To give us an idea it is enough to say that some turbines work at about 30,000 r.p.m. And the main rotor at about 300 rpm. All this is achieved by reducing gear sets.

As far as flight controls are concerned, the difference with conventional aircraft is much greater since the supporting surfaces (blades) are at the same time the control surfaces.

The rotor heads are of great technical complexity, although the use of composite materials tends to simplify their design and maintenance. An articulated rotor (the type most commonly used for its efficiency) allows the turning movements on the longitudinal axis, up / down and forward / backward. In addition, the blades themselves undergo deformation and flexing while rotating. All this makes the maintenance of the rotors a very important aspect.

The blades have to be matched so that their weight is as uniform as possible (all have equal weight), the tolerance being in the difference of weights of tens of grams since of a mass imbalance in rotation causes vibrations And, ultimately, structural damage to them and to the rest of the components of the helicopter.