A helicopter is one of the most versatile aircrafts ever built. It can be used almost anywhere on land or at sea, whether it’s emergency medical service, firefighting or transportation to the oil platforms. With its ability to take off and land vertically and hover, it becomes a very useful tool. On the other hand it is not a very effective aircraft when it comes to flying long distance. This is because of its slow forward speed compared to an airplane.
Flying a helicopter the first time is like learning how to ride bike – you keep falling off. Just to keep the helicopter over a spot steadily, normally takes around three hours of flying. The trick is to make your inputs on the controls before the helicopter moves. It is a very sensitive and unstable aircraft, but safe if treated correctly.
There are three main parts of a helicopter. The main rotor, which produces a vertical lift vector, a tailsection which counteracts the force called torque made by the mainrotor, and the third part is the fuselage. The main rotor can consist of two or more rotorblades. The Russian helicopter MI-28 has eight rotorblades with a total lift capability of 44,000 lbs. Think of each blade as a wing on an airplane. The difference is that this wing is being rotated around the rotormast. When it travels around, lift is created as in an airplane. Newton’s third law says that for every action there is an equal and opposite reaction. Since the blades, on most Western helicopters, travel counterclockwise, a force is produced in the clockwise direction. This is called torque and this will try to twist the helicopter to the right. To counteract this a helicopter has a tail with a tailrotor mounted vertically producing lift in a horizontal direction.
Maneuvering the helicopter is done by four controls. The cyclic controls the main rotor, or rotordisc. This is done by two plates, one stationary and one rotating – called swashplates. When the cyclic is moved, pressure is applied to the stationary swashplate and transferred to the rotating plate. This tilts the disc in the direction the cyclic was moved. The total lift will now consist of one horizontal and one vertical vector allowing the helicopter to move in the respective direction. The collective twists the blades, changing the angle of attack on each rotorblade and more lift is produced. The pedals will increase or decrease the amount of lift on the tailrotor allowing the helicopter to move around its vertical axis. The collective has also a throttle similar to a throttle on a motorbike, which controls the RPM on the engine, mainrotor and the tailrotor.
Flying the helicopter requires a great deal of coordination. Most of the maneuvers require inputs from all the controls. Everything has to be done gently with no abrupt movements and within the limitations of each respective aircraft. There are many hazards in flying a helicopter, and not just from the helicopter itself. Helicopters are built to fly at low altitudes between the surface and 2,000 feet above the ground. Obstacles like wires, trees and buildings make the helicopter fragile if no precautions have been made. Emergency landings are another factor that is different from an airplane. The airplane will continue to fly, or glide, without the engine running. A specific airplane has a glide ratio of 20:1, which means it can glide 20 feet for every 1 foot of altitude loss. The helicopter needs either sufficient altitude or airspeed in order to make a safe landing. A Robinson R-22 has a ratio of 4:1. An emergency landing is made possible by a freewheeling unit that allows the rotorblades to keep on rotating when disengaged from the engine. It is the same as a propeller leaf falling down while rotating. This is called autorotation. The vertical speed is about 15 mph, the same speed as a skydiver with the parachute open. Just before the helicopter reaches the ground a flare is initiated. This increases the rotor rpm and more lift is available in order to cushion the landing. Emergency landings can be made down to any available spot like baseball fields, parking lots, roofs or streets.
Most of all, helicopter flying is fun because everything can be done with perfection. It can be used to do any job almost anywhere.
