Lesson 1: How can you hover a helicopter?

The pilot has 3 control devices or operating options: the cyclic stick (cyclic), the collective pitch (collective) and the pedals (pedals). There is actually also the throttle at the end of the collective, but for simplicity's sake we will leave that out. Also because on most modern helicopters it is controlled automatically.

The collective makes it possible to increase or decrease the lift that the rotor blades develop. By moving the collective up, the rotor blades are tilted more, causing them to move upwards (and with them, of course, the helicopter). Compare it with your hand which you stick out of a moving car and let move upwards by tilting it. By tilting the rotor blades, they will also catch more wind, drag as we call it, causing the rotor speed to want to decrease. Modern helicopters operate at a fixed rotor speed, so the engine will produce more power. Because the engine makes the rotor blades turn in a certain direction, the helicopter itself will want to turn in the opposite direction.

To solve this problem we have the tail rotor, which we operate with the pedals. The tail rotor also turns at a fixed speed, but here too we can tilt the blades of the tail rotor, now using the pedals. By operating the pedals we can control the thrust of the tail rotor. A helicopter with a rotor that turns to the left will therefore want to turn to the right itself. The tail rotor thrust, however, will push the tail to the right, allowing us to bring the nose back in the desired direction.

So with the collective and the pedals we can move up and down and we can keep the nose of the helicopter in a certain direction. To move forwards, backwards and sideways we use the cyclic. By moving this control stick in a certain direction, the rotor disc will also tilt in the same direction, and so the helicopter will also move in this direction.

It all sounds logical, but… as soon as you use one of these controls, you will also have to make a correction with the others. When you move the cyclic stick forward, for example, the rotor disc also tilts forward and the helicopter will also move forward. The nose of the helicopter, however, also goes down, causing the helicopter to descend. To counter the descent, we move the collective up. This requires the engine to deliver more power, which makes the nose turn to the right. To keep the nose in the same direction, we therefore have to use the pedals and push the left pedal.

On top of that, a helicopter, unlike an aeroplane, is always unstable and by no means wants to hang still. The helicopter will tend to make a swinging motion that grows larger and larger, causing the pilot's corrections to become larger and larger.

That, at least, is how it seemed to me when I started my first helicopter lessons in the past. But… practice makes perfect and also gives a lot of flying pleasure…

Credits

• Source: Flight Principles Course – C. Comyn @Toran
• Photo & drawings © C. Comyn – Toran
• Text © C. Comyn – Toran

Article source: https://www.helispot.be/hs/page/detail.asp?oid=D2D5E4D2