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Basic Flight Manoeuvres

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This section provides an overview of basic helicopter flying skills and how to perform them.

Hovering

When a helicopter is in a hover, it is typically a few feet above the ground, in a 'fixed' position. To hover, a pilot must use all of the controls in order to maintain position and attitude, and it requires a great deal of concentration.

Best practice is to look at a reference point that is not too close, so as to avoid over-controlling. Turning of the helicopter is compensated for by yaw control using the pedals. Lateral movements and attitude are compensated for by the cyclic (as is the case with forward / backward movements). The skills required are in knowing when to use the pedals, and when to apply cyclic control, since it is not unusual for the pilot to, initially, sometimes confuse lateral movement with turning. This will lead to instability. The second skill to acquire is how to get a feeling for the helicopter when applying cyclic control. When doing so, the helicopter moves in a particular direction. When the cyclic is returned to neutral (as it should be), the helicopter will still move in the initiated direction. In order to stop the helicopter, the cyclic must be briefly moved in the opposite direction. Logically, this must be done in anticipation rather than in response to an actual situation.

In using the controls, it is important to make only small adjustments, and to not wait too long before making compensatory changes. All this requires practice.

 

Straight and level flight

When in straight and level flight, the helicopter flies with a given constant heading and speed, while maintaining a constant altitude. Altitude is controlled by the collective’s setting, and speed and attitude control by the cyclic’s setting. To maintain a constant heading, the pilot looks for two distant reference points that are in his flight path. The horizon is used as the reference when making attitude adjustments. The cyclic is used to tilt the rotor disc towards the position that matches the desired speed. Of course, there is interaction between all of the controls. For example, when the speed of the helicopter is changed, the amount of lift produced by the rotor disc is affected, and so corrective collective control is required to maintain a constant altitude. A changed collective setting (power setting) on the turn creates further torque, and can thus influence the heading, thereby requiring corrective pedal action.

 

In normal level flight situations, a helicopter will fly from altitudes of 300 feet and above.

Climbs and descends

A climb is started by moving the collective backwards to get the desired climbing attitude. This will slow the forward speed down. When the helicopter is at the desired forward climbing speed, more power (more collective) can be added to achieve the desired rate of climb. The heading will change because of the changed torque setting. This must be compensated for by applying pedal control. The maximum rate of climb is usually reached with a forward speed of around 30 to 40 knots in a light helicopter.

To start a descent, the collective is lowered. In response, the helicopter starts to sink. Pedal control is needed to correct for heading changes. After the descent has begun, the desired descent airspeed is realized by applying cyclic pressure.

Turns

In forward flight, a turn is started by applying lateral cyclic control in the desired direction, which results in a banked turn. Usually, turns are made with a banking angle of around 15 degrees. In general, turns will demand more power to maintain a constant altitude, as the banking will result in a loss of lift. During the turn, the pedals are used to keep the helicopter balanced.

Hover to forward flight

To transit from a hover to forward flight while maintaining altitude, the following procedure has to be followed. Firstly, forward cyclic control is used to start moving forwards. When the helicopters tilts, lift will, in theory, decrease. However, when the helicopter gains forward speed, the rotor system will produce substantially more lift because of the higher airspeed (a phenomenon called translational lift). Therefore, when gaining speed, collective control must be lowered to maintain the same altitude. At some point, airspeed is such that even higher airspeeds will no longer produce extra lift. From then on, more forward speed by the application of more forward cyclic will result in a decrease in lift, and the collective has to be raised to maintain altitude.

Hover to climb

Hover to climb is started by applying forward cyclic. As the helicopter starts to move, more collective is needed to compensate for the loss of ground effect. When the forward speed increases, the rotor system encounters a higher airspeed and the helicopter starts to climb (translational lift). The rate of climb is set by applying appropriate collective control, and by applying cyclic control to achieve the desired climb attitude.

Forward flight to hover

To get into a hover from forward flight, the first step is to reduce the forward speed by applying backward cyclic. When the helicopter slows down, the attitude must be stabilized again. If the speed gap is significant, the speed can be reduced by several steps. The collective is lowered to get at the desired descent rate. The cyclic is used to maintain the desired approach speed, usually around 30 to 40 knots. When near to the hovering spot, the helicopter's forward speed is reduced by performing a flare. In a flare, the rotor disc is tilted backwards, reversing thrust and causing the helicopter to slow down significantly. When the rotor disc is tilted backwards, the rotor efficiency and lift will increase a great deal, and so the collective should be lowered to prevent a sudden increase in altitude. Before the airspeed reaches zero, the cyclic must be moved forwards to prevent flying backwards. The collective should be increased when the helicopter leaves the flare, to compensate for a loss in lift.

Autorotation

In the event of an engine failure, a helicopter can still be flown by 'sailing' through the air by using the rotor system as a 'windmill'. At the time when there is no power to drive the rotor system, a free-wheel system prevents the rotor system from ceasing to rotate. However, the rotor system will not rotate by itself. It is driven by the air it encounters in the descent. In order to get this to work, the collective must be completely lowered, which must be done while the rotor system is still rotating. This means that, in the event of engine loss, fast action is required.

The rotor system is designed in such a way that, with a completely lowered collective, the inner part of the rotor system is driven by the wind to maintain rotation in the same direction as when under engine power. The middle section of the rotorblades works, more or less, in the same manner as when in normal operation, and provides the necessary thrust vector (lift), albeit less than is normally the case.
The helicopter should, ideally, maintain forward speed when in autorotation. When approaching the ground, the helicopter is stopped and landed in a flare. The flare can be carried out by using the kinetic energy that is stored in a rotating rotor system. When carried out properly, an autorotation is a completely safe manoeuvre.


Note that all these manoeuvres can be practised with flight simulation software.

Learning to Fly Helicopters

This book covers helicopter flying skills. It firstly explains all necessary helicopter flying’ theory. Secondly, it covers all flying manoeuvres, which are described and explained in detail. It is this, the largest part of the book, which makes it a useful guide to how to learn to fly helicopters. The flying exercises are also a great help. The book’s emphasis really is on explaining how to fly helicopters, which sets it apart. A must have for everyone who wants to get their helicopter flying licence.







FAA Rotorcraft Flying Handbook

This handbook is written and published by the FAA. It covers both helicopters and gyroplanes. The manual is very readable and contains lots of illustrations. The text covers all relevant subjects, like aerodynamics, flight controls, basic flight manoeuvres, attitude instrument flying, and night operations. A valuable resource for everybody training for their FAA helicopter licence.

Note that you can also download this text for free at http://www.faa.org.





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HeliStart is authored by Peter Goossens.


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