FlightGear Flight Simulator/Advanced/Helicopters

Preface In principle everything that applies to real helicopters, applies also to helicopters in FlightGear. It is important to be familiar with 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. 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). Tail rotor controls For controlling the tail rotor you should have pedals, or at least a joystick that can twist 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 --enable-auto-coordination in either the FlightGear Qt launcher or the command line. Joystick 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 both have advantages and disadvantages. The mouse won't feel natural, but you can change the control travel in mice.xml to your need. By decreasing the factor you can increase the control travel way and have less sensitive controls, which might improve the handling. Keyboard 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. In my opinion the Bo105 is the easiest to fly, since it reacts substantially more directly than other helicopters. 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. 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. Controls 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 cyclic blade control. Next there is the 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 the helicopter around the vertical axis. The number of revolutions of the rotor is kept constant (if possible) by the aircraft. Behavior of helicopters Helicopters are naturally unstable. It is like balancing a ball sitting on another bigger ball, which is sitting on a much bigger ball. Every control input leads to another control input to compensate: So if you increase the collective, you have to push the pedals to compensate the torque. With this you are increasing the tail rotor thrust and the helicopter wants to drift to the side. So you have to compensate this with the stick... And so on, and so on. This makes helicopter flying much more difficult than fixed-wings. But with some practice it will become as easy as riding a bicycle! 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 of the thrust controller). Equally, "full power" has the thrust controller at idle. Start the engine by pressing }. After few seconds the rotor will start to turn and accelerates slowly. Keep the stick and the pedals approximately centered. Wait until the rotor has finished accelerating. For the Bo105 there is an instrument 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!). 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: Press } to start the turbines; use Automatic startup from the aircraft menu or follow the specific startup tutorial, depending on the helicopter. Disengage parking or rotor brake (if applicable). Wait for your turbine to come to full speed. Push the throttle down, not up. Pushing up makes the chopper go down. When at desired altitude, push throttle to about 60%. Fly freely. 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. In the air To avoid the continual frustration of trying to achieve level flight, you may want to try forward flight. After take off continue pulling the collective a short time and then lower the nose slightly using the control stick. The helicopter will accelerate forward. With forward speed the tail rotor does not have to be controlled as precisely due to the relative wind coming from directly ahead. Altogether the flight behaviour in forward flight is quite similar to that of a badly trimmed airplane. The "neutral" position of the stick will depend upon airspeed and collective. Transitioning from forward flight to hovering is easiest if you reduce speed slowly by raising the nose of the helicopter. At the same time, reduce the collective to stop the helicopter from climbing. As the helicopter slows, "translation lift" is reduced, and you will have to compensate by pulling the collective. When the speed is nearly zero, lower the nose to the position it was when hovering. Otherwise the helicopter will accelerate backwards! You may wonder about the heli banking to the side. Don't worry, that's 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, for example while hovering. In cruise the fins will take over more and more of 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. That's the reason why on modern helicopters like the EC135 the attitude indicator is even mounted with a bank on the panel.https://wiki.flightgear.org/Howto:Fly_a_helicopter See also Helicopter flight controls (Wikipedia) References