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Howto:Fly a helicopter: Difference between revisions
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== Preface == | == Preface == | ||
In principle everything that applies to real helicopters, applies also to helicopters in [[FlightGear]]. It is important to be familiar with [[http://www.cybercom.net/~copters/pilot/maneuvers.html fundamental helicopter manoeuvres]]. Some details are simplified in FlightGear, in particular the engine handling and some overstresses are not simulated or are without any consequence. In FlightGear it is not possible to damage a helicopter in flight. | |||
[[File:bo105_cockpit.jpg]] | [[File:bo105_cockpit.jpg]] | ||
Since the release of FlightGear 0.9.10, important improvements have been made to the helicopter [[Flight dynamics model|flight model]]. For this reason, version 1.0.0 or later should be used. With these improvements the helicopter flight model of FlightGear should be quite realistic. A notable exception is “vortex ring conditions”. These occur if you descend too fast and perpendicularly (without forward speed). The heli can get into its own rotor downwash causing the lift to be substantially reduced. Recovering from this condition is possible only at higher altitudes. There is video of a Sea King helicopter which got into this condition during a flight demonstration and touched down so hard afterwards that it was completely destroyed | Since the release of FlightGear 0.9.10, important improvements have been made to the helicopter [[Flight dynamics model|flight model]]. For this reason, version 1.0.0 or later should be used. With these improvements the helicopter flight model of FlightGear should be quite realistic. A notable exception is “vortex ring conditions”. These occur if you descend too fast and perpendicularly (without forward speed). The heli can get into its own rotor downwash causing the lift to be substantially reduced. Recovering from this condition is possible only at higher altitudes. There is [http://www.youtube.com/watch?v=IUzhRKn9534 video] of a Sea King helicopter which got into this condition during a flight demonstration and touched down so hard afterwards that it was completely destroyed. | ||
=== Control hardware === | === Control hardware === | ||
==== Stick and Pitch control ==== | |||
On the hardware side a use of a good [[joystick]] is recommended:A joystick without centering springs is recommended for cyclic control. You can achieve this with a normal joystick by removing or disabling the centring spring(s), or you could use a [[force feedback]] joystick with a disconnected voltage supply. Further, the joystick should have a “thrust controller” (throttle). | On the hardware side a use of a good [[joystick]] is recommended:A joystick without centering springs is recommended for cyclic control. You can achieve this with a normal joystick by removing or disabling the centring spring(s), or you could use a [[force feedback]] joystick with a disconnected voltage supply. Further, the joystick should have a “thrust controller” (throttle). | ||
==== Tail rotor controls ==== | |||
For controlling the tail rotor you should have pedals, or at least a joystick that can twist in in a yawing motion. You may have to turn off auto-coordination, as you need full controls for the tail rotor. This can be done by adding the flag <code>--enable-auto-coordination</code> in either the [[FlightGear Qt launcher]] or the [[command line]] | |||
For controlling the tail rotor you should have pedals or at least a | |||
You have to turn off auto-coordination, as you need full controls for the tail rotor | |||
==== Joystick ==== | |||
The deflections of a real heli stick can be also asymmetrical depending on the helicopter, while our joysticks always have symmetrical deflections. | While a joystick feels more natural, it won't have the same deflections like a real heli stick. In most cases it is even less, which makes the heli in FlightGear more difficult to control than the real thing. Usually the full control travel way of a real helicopter stick is between 6 inches and 11 inches depending on the helicopter. The deflections of a real heli stick can be also asymmetrical depending on the helicopter, while our joysticks always have symmetrical deflections. | ||
==== Mouse ==== | |||
A mouse can be also used, Joystick and mouse has both advantages and disadvantages. The mouse won't feel natural, but you can change the control travel in <code>mice.xml</code> to your need. By decreasing the <factor> you can increase the control travel way and having less sensitive controls, which might improve the handling. | |||
==== Keyboard ==== | |||
Flying helicopters by keyboard is not possible, as it won't provide sensitive enough control! | Flying helicopters by keyboard is not possible, as it won't provide sensitive enough control! | ||
== Getting started == | |||
== | === Launch === | ||
The number of available helicopters in FlightGear is increasing rather quickly. As helicopters have become more popular in FlightGear, many others have been developed. Each of them have their unique flight behaviour. | The number of available helicopters in FlightGear is increasing rather quickly. As helicopters have become more popular in FlightGear, many others have been developed. Each of them have their unique flight behaviour. | ||
In my opinion the [[Eurocopter Bo105|Bo105]] is the easiest to fly, since it reacts substantially more directly than other helicopters. | In my opinion the [[Eurocopter Bo105|Bo105]] is the easiest to fly, since it reacts substantially more directly than other helicopters. | ||
The Bell UH-1 is also recommended, though behaving | The Bell UH-1 is also recommended, though behaving completely different as the Bo105. Nevertheless both models shows very realistic handling qualities, are tested by their real pilots, and their real counterparts are used in some armies for training of pilot novices. | ||
The Robinson R44, is also very easy to fly, although possibly unrealistically so. | The [[Robinson R44]], is also very easy to fly, although possibly unrealistically so. | ||
Once you have loaded FlightGear, take a moment to centralize the controls by moving them around. However, as noted below, the throttle should be at maximum to equal the same as low throttle. | Once you have loaded FlightGear, take a moment to centralize the controls by moving them around. However, as noted below, the throttle should be at maximum to equal the same as low throttle. | ||
[[File:s76c_landed.jpg]] | [[File:s76c_landed.jpg]] | ||
=== Controls === | |||
The helicopter is controlled by four functions. The | The helicopter is controlled by four functions. The stick controls two of them, the inclination of the rotor disc (and thus the inclination of the helicopter) to the right/left and forwards/back. Together these functions are called [https://en.wikipedia.org/wiki/Helicopter_flight_controls#Cyclic cyclic blade control]. Next there is the [https://en.wikipedia.org/wiki/Helicopter_flight_controls#Collective collective blade control], which is controlled by the thrust controller. This causes a change of the thrust produced by the rotor. Since the powering of the main rotor transfers torque (as a twisting or turning force) to the fuselage, this must be compensated by the tail rotor. Since the torque is dependent on the collective and on the flight condition as well as wind can add additional torque on the fuselage, the [[tail rotor]] is also controlled by the pilot using the pedals. If you push the right pedal, the helicopter turns to the right (!). The pedals are not a steering wheel. Using the pedals you can yaw helicopter around the vertical axis. The number of revolutions of the rotor is kept constant (if possible) by the aircraft. | ||
[[File:ec135_in_the_air.jpg]] | [[File:ec135_in_the_air.jpg]] | ||
=== Behavior of helicopters === | |||
Helicopters are natural unstable. It is like balancing a ball sitting on another bigger ball, which is sitting on a much bigger ball. | Helicopters are natural unstable. It is like balancing a ball sitting on another bigger ball, which is sitting on a much bigger ball. | ||
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== Lift-Off == | == Lift-Off == | ||
First reduce the collective to minimum. To increase the rotor thrust, you have to “pull” the collective. Therefore for minimum collective you have to push the control down (that is the full acceleration position | |||
{{Note|Increasing the throttle (pushing the throttle forward) will cause the helicopter to go down, not up. Likewise, decreasing the throttle (pulling back on the throttle) will cause the helicopter to go up.}} | |||
First reduce the collective to minimum. To increase the rotor thrust, you have to “pull” the collective. Therefore for minimum collective you have to push the control down (that is the full acceleration position of the thrust controller). Equally, “full power” has the thrust controller at idle. Started the engine by pressing {{key press|<nowiki>}</nowiki>}}. After few seconds the rotor will start to turn and accelerates slowly. Keep the stick and the pedals approximately entered. Wait until the rotor has finished accelerating. For the Bo105 there is an instruments for engine and rotor speed on the left of the upper row. The RPM percentage of the rotor should be at 97-100%. | |||
Once rotor acceleration is complete, pull the collective very slowly. Keep your eye on the horizon. If the heli tilts or turns even slightly, stop increasing the collective and correct the position/movement with stick and pedals. If you are successful, continue pulling the collective (slowly!). | Once rotor acceleration is complete, pull the collective very slowly. Keep your eye on the horizon. If the heli tilts or turns even slightly, stop increasing the collective and correct the position/movement with stick and pedals. If you are successful, continue pulling the collective (slowly!). | ||
As the helicopter takes off, increase the collective a little bit more and try to keep the helicopter in a levelled position. The main challenge is reacting to the inadvertent rotating motion of the helicopter with the correct control inputs. Only three things can help you: practice, practice and practice. It is quite common for it to take hours of practice to achieve a halfway good looking hovering flight. | As the helicopter takes off, increase the collective a little bit more and try to keep the helicopter in a levelled position. The main challenge is reacting to the inadvertent rotating motion of the helicopter with the correct control inputs. Only three things can help you: practice, practice and practice. [[It is quite common for it to take hours of practice to achieve a halfway good looking hovering flight.]] It should be noted that the stick position in a stable hover is not the centre position of the joystick. | ||
Quick Reference: | Quick Reference: | ||
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# Disengage parking or rotor brake. (If applicable) | # Disengage parking or rotor brake. (If applicable) | ||
# Wait for your turbine to come to full speed | # Wait for your turbine to come to full speed | ||
# Push the throttle | # '''Push the throttle down, not up.''' Pushing up makes the chopper go down. | ||
# When at desired altitude, push throttle to about 60% | # When at desired altitude, push throttle to about 60% | ||
# Fly freely | # Fly freely | ||
{{Note|Making small inputs will lead you to success! Most helicopters are controlled just by small inputs by the fingers or the hand, the forearm resting on the thigh.}} | |||
=== Video: Takeoff to Hover === | |||
The following video is showing a takeoff into hover. The HUD will give you an impression of the needed position of your controls. | The following video is showing a takeoff into hover. The HUD will give you an impression of the needed position of your controls. | ||
{{#ev:youtube|T0NpG7u0Ezs}} | {{#ev:youtube|T0NpG7u0Ezs}} | ||
== In the air == | == In the air == | ||
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You may wonder about that the heli banking to the side. Don't worry, thats normal for helicopters. Due to the thrust of the tail rotor and the fins which also prevents the effect of the main rotor torque, the helicopter is pushed to one side. The helicopter would drift laterally. So to keep the heli straight you have to counteract this effect. That means you have to steer the helicopter so that you don't drift away- so bank the heli against the drift. The more tail rotor thrust you give, the more banking you will have. As an example while hovering. In cruise the fins will take over more and more the work of the tail rotor and will produce the same effect. | You may wonder about that the heli banking to the side. Don't worry, thats normal for helicopters. Due to the thrust of the tail rotor and the fins which also prevents the effect of the main rotor torque, the helicopter is pushed to one side. The helicopter would drift laterally. So to keep the heli straight you have to counteract this effect. That means you have to steer the helicopter so that you don't drift away- so bank the heli against the drift. The more tail rotor thrust you give, the more banking you will have. As an example while hovering. In cruise the fins will take over more and more the work of the tail rotor and will produce the same effect. | ||
The side of the banking depends on the direction of turn of the main rotor: Counterclockwise --> left banking. Clockwise --> right banking. | The side of the banking depends on the direction of turn of the main rotor: Counterclockwise --> left banking. Clockwise --> right banking. | ||
That's the reason why on modern helicopters like the EC135 the attitude indicator is even mounted with a bank on the panel. | That's the reason why on modern helicopters like the [[EC135]] the attitude indicator is even mounted with a bank on the panel. | ||
=== Video: Hover to Departure === | |||
The following video is showing the transition from hover to forward flight. The HUD will give you an impression of the needed position of your controls. | The following video is showing the transition from hover to forward flight. The HUD will give you an impression of the needed position of your controls. | ||
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{{#ev:youtube|DaL99X4JtJY}} | {{#ev:youtube|DaL99X4JtJY}} | ||
=== Video: Demonstration of the Effective Translational Lift (ETL) === | |||
The following video demonstrates the ETL, or also called translational lift effect. The lift of the rotor will increase by passing a certain relative airspeed, usually about 20ktn. | The following video demonstrates the ETL, or also called translational lift effect. The lift of the rotor will increase by passing a certain relative airspeed, usually about 20ktn. | ||
| Line 114: | Line 105: | ||
{{#ev:youtube|IHcyb7gZIh4}} | {{#ev:youtube|IHcyb7gZIh4}} | ||
=== Video: Hover Turns === | |||
The following video shows how to turn the helicopter in a hover about a spot. | The following video shows how to turn the helicopter in a hover about a spot. | ||
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{{#ev:youtube|Hj6q_xl7AFc}} | {{#ev:youtube|Hj6q_xl7AFc}} | ||
== Back to Earth I == | == Back to Earth I == | ||