The incredible science behind how a helicopter flies
Did you know already?
Despite the apparent ease, hovering is one of the most difficult maneuvers in helicopters.
Helicopters are powered by rotating blades as rotors. This distinguishes them from fixed aircraft, such as jet engines or ultralights.
All aircraft are destroyed by the same principle. When the front tip of a wing is lifted, it forces the air that flies over it to flow faster than the air below. This means that at any moment there is less air above the wing than under it. This imbalance causes lift, and literally sucks the plane up. A flying airplane flies because of the lift generated by air flying over its wings. This requires moving air (as in the case of gliders) or some form of propulsion.
In contrast, Rotary wing aircraft produce their own thrust by moving their wings against the air. The rotors of a helicopter actually perform the same function as the wings of an aircraft, except that the wings of an aircraft need to thrust to produce a forward motion. Sailplanes that have no engine must drop their height to get forward (which they reach by lowering their nose). A helicopter engine, on the other hand, supplies the rotors and does not provide any thrust directly; The tiny thrust produced by the exhaust from the engine is negligible in the larger scheme.
The ability to create your own lift gives the helicopter obvious advantages over fixed aircraft. Helicopters can stand out and be represented (although an exclusive class of aircraft can do that), are able to hover in the air, and are much more maneuverable when space is on a premium.
But this also makes the control helicopter much more difficult to control than aircraft. The basic shape of the aircraft allows them to glide passively forward for a considerable distance, even if the pilot and propulsion stops. However, the flexible, active nature of the helicopter means that it is not designed to slip. It must always be kept in the air without any help from the laws of physics. Pilots must always insert the helicopter’s input, even if it is floating. The rotating mechanism also limits the top speed of a helicopter and makes them inherently slower than fixed aircraft.
So how exactly do helicopters fly, and more importantly, how to control helicopters?
Helicopters are controlled by a combination of three controls:
Working a helicopter
This controls the angle of attack (AOA) of all rotor blades – the name. The AOA is the angle formed by the raised or lowered blade against the imaginary plane of its base.
When the angle of attack is increased, the air flowing over the top of the blades must flow faster and trigger the lift. Likewise, the angle of attack must be reduced to land a helicopter.
The collective is to the left of the pilot, at the base of his seat. It is often accompanied by a motor-wheel-like spin handle throttle which is rotated sideways to increase or decrease the angle.
As the angle of incidence increases, the air resistance of the rotors also increases. To counteract this, the engine speed must be increased to maintain a constant rotor speed. Thus, the throttle is paired with either the selector lever, or a component known as the governor, is incorporated into the chopper. The controller automatically changes the engine speed when the angle of attack is changed and keeps the rotor speed constant.
The cyclic control of the direction of the helicopter. It is called the cyclic control because it cyclically changes the angle of each sheet. Instead of raising a single blade, the cyclic system changes the elevations of certain points in the rotating portion of the swashplate. This in effect causes the rotor disk (the rotating portion of the wobble plate) to tilt in a certain direction.
This produces the same aerodynamic effect as the lifting, only with the added element of a lateral direction. This drives the copier in this direction.
The cyclic control is often found in the form of a joystick, either in front of the driver’s seat or between the pilot and the copilot. Like any other joystick, the direction of the joystick corresponds with its effect, ie when the cyclic control is shifted to the left, the rotor disc tilts to the left and the chopper moves to the left.
According to Newton’s third law of motion, each action has an equal and opposite reaction – the rotation of the main rotor causes the rest of the helicopter to rotate in the opposite direction. This is called a torque reaction. The rear rotor on helicopter counts this effect and keeps the chopper in a straight line. The rear rotor can be used as a rudder.
Two anti-torque pedals, located on the pilot’s feet, control the pitch of the rear rotor disc. When the right pedal is pressed, the rear rotor disc is turned to the right, and the nose of the helicopter will turn to the right and vice versa. This is just as the main rotor lifts, only sideways. These pedals are used to induce yawing and to turn the helicopter. When used during hovering, the anti-torque pedals allow a helicopter to rotate 360 °.
This is what helicopters defined better than anything else. Keeping a helicopter stationary in the air can look easy, but in reality it is one of the most difficult things that a pilot has to do.
To hover, a pilot must first stop any directional movement by bringing the cyclic control to the center. Then, he must stabilize the collective lever at the required height and make the necessary adjustments to the yaw pedals to maintain the exact position with respect to all three axes.
Helicopters are used to expose forest fires, rescue work and, of course, in the armed forces. They are crucial civilian and military equipment around the world, and with their extremely useful attributes, this is hardly a surprise.