Training for Helicopter Flights: Flight Controls and Their Purpose in the Air

Helicopter flights are controlled through four sets of pedals, sticks and levers. They are split into the following categories – the cyclic control; the anti-torque control; the collective control; and the throttle.
To understand the controls that are used during helicopter flights, it is first necessary to understand something about the machine itself. A helicopter works by developing lift and thrust through rapidly moving rotors, both above the cabin and behind it. The rotational lift delivered by the main vanes keeps the helicopter in the air, and by slightly tilting the nose may also be used to drive it forwards. The vanes in the tail help stabilise the helicopter and to steer it. In effect, the forces generated by the main vanes plus the tail vanes are held in opposition to keep the machine correctly oriented: much in the same way that a heavy object may be lifted easily from the ground, and kept level, by applying both a pushing and a pulling force to each end. 

The four groups of controls, then, produce the following effects.
A cyclic control, which is normally located as a stick held between the pilot’s legs, changes the angle of the rotors. By doing this, the helicopter may be moved into different positions in the air – steered, in other words. The cyclic control essentially works like a joystick: pull right and the machine goes right; push forwards and it dives; pull up and it climbs; pull left and it goes left. 

Because the helicopter is powered by rotary motion, there is a delay between pushing the stick forward (for instance) and the bite of blades in the air causing the required downward motion. 

Anti-torque pedals are used (with the feet) to maintain control of the helicopter’s nose. Torque forces produced by different speeds in the rotor vanes may cause the nose to skew itself, essentially resulting in the rotor vanes trying to drag a sideways-facing object through the air. The torque pedals are used to combat this effect and keep the nose pointing in the direction of travel. 

The collective control is also known as the pitch control. Collective control refers to the ability to alter the angle of all the turning rotor vanes at once, with a correspondingly more severe effect on the motion of the craft. Where the craft is flying with a  level nose, using the collective itch control makes the machine climb or drop. If the nose is angled forward, the collective control becomes an accelerator or decelerator. 

The throttle is key to keeping the rotors turning at the right speed. Depending on the other conditions presented by the use of the other three control types, the overall speed of rotation will have different effects: and there is a lowest threshold beyond which there is no longer enough power generated to keep the machine in the air. 

A helicopter has very little dynamic stability. This means that its core defining task – the ability to hover, whichonly one aeroplane can successfully do – is also its least likely. However, the controls used in helicopter flights are specifically designed to control the four forces and directions that produce the hovering ability: so while the shape and weight of the machine makes it dynamically unlikely to hang in one place, the skill of the pilot allows it to do just that.

Author bio: Naomi Watson is a helicopter training instructor. She has amassed a huge number of hours in helicopter flights over the years.
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1 comments:

  1. Great post. Very informative. Thanks for sharing
    http://www.shorelinehelicopters.co.nz/

    ReplyDelete