Gyro gain and operation mode
The tail gyro system of the AR7210BX receiver helps to keep the helicopter's tail in position while flying around. It makes the rudder only react to stick inputs but not to external effects. Before the first flight, you have to set the correct amount of gyro gain in order to adapt the reaction of the gyro system to your specific helicopter model. Additionally, you have to choose between two different operation modes:
- Normal-Rate mode - here the tail gyro of the AR7210BX only acts as dampening that decelerates sudden rotations caused by external influences. Slow, constant rotational movements will not be compensated. Thus the tail does not drift in hover due to the main rotor torque, a perfect mechanical adjustment of the tail rotor is essential (see the section to Setup menu point E & F). But even with perfect mechanical adjustment you will always encounter some drift on the rudder axis due to crosswinds and the pilot has to constantly perform corrections when doing hovering flight. In high-speed flight on the other hand the tail will be aligned in flight direction by the wind, so curves can be flown very dynamically and the pilot doesn‘t have to constantly concentrate on controlling the rudder.
- HeadingLock mode - in this mode the tail is actively controlled by the gyro system. You will barely feel any external influences. By giving rudder stick input, the pilot only commands the gyro how fast it has to turn the tail. When the stick is in center position the tail gyro will ensure that the tail keeps locked into position by any means. This simplifies the control significantly. In hovering flight the beginner can fully concentrate on the control of cyclic and collective pitch and the advanced pilot can perform 3D - flight maneuvers such as backwards flying quite easily. The only disadvantage of HeadingLock-Mode is that the rudder must be steered by the pilot when flying curves. Otherwise the gyro will try to keep the tail aligned with the initial direction.
When setting up the system for the first time, start with medium gain in HeadingLock mode. Then readjust the gain as necessary:
Low gain will cause the rudder control feel weak, the tail will break out on collective pitch inputs and it will stop with overshoots. Increase the gain step by step. You will feel the tail having more and more precise stops and hold better and better on jerky pitch inputs. But watch out! If the gain gets too high, the stops will bounce back quickly and wagging will appear in fast forward or backward flight (or even on take-off). In this case land immediately and reduce the gain! For optimum performance set the gain as high as possible, just before the tail rotor starts to wag in fast forward flight.
Tail gyro response
In addition to the gyro gain adjustment there is a parameter called gyro response which helps to optimize the precision of the gyro. Increasing the gyro response will cause a harder stop and quicker response to rudder stick inputs. But if the response is too high, the tail will bounce back after a hard stop and feel spongy when making fast direction changes. If the response is set too low on the other hand, the rudder control feels dull and stopping might be too soft. Ideally the tail should stop perfectly to the point without making any flapping noises.
Before adjusting the gyro response make sure the maximum possible tail gyro gain has already been determined as described above! The gyro response can be considered as some sort of fine-tuning and adjusting this parameter will not have any significant effect if the gyro is not operating correctly in general. Also note that after adjusting the tail gyro response you may have to readjust the tail gyro gain once again, as these parameters interact to each other.
For better tail gyro performance also check for correct servo horn length. In case you can set the gyro gain only to a very low value and the rudder tends to oscillate very easily, move the linkage ball further inwards to the center of the servo horn. If on the other hand you have a very large amount of gain and the gyro still does not seem to be capable of holding the tail rotor in any flight condition, move the linkage ball on the servo horn further out from the center, to get faster response speed when the gyro controls the rudder servo. Also you may use different (larger) tail rotor blades or higher tail rotor speed to achieve better holding force.
The control loop for the cyclics depends on two major parameters: Cyclic gain and Cyclic feed forward.
In general the higher the gain, the harder the helicopter will stop after cyclic moves and the more stable and exact the helicopter will fly. But if the gain is too high, the helicopter will tend to oscillate at high frequency especially on the elevator axis. Due to their low mass, this behavior will occur sooner on small helicopters, so typically these do not need as much gain as large helicopters.
On the other hand, in case the gain is too low, the helicopter does not stop precisely and overshoots the more or less after a cyclic movement. Additionally, it feels unstable and sluggish in fast forward flight and when hovering. In general, low gain will allow the helicopter to have more life of its own and so it will not react to stick inputs as precise and immediate as the pilot expects it.
Ideally you set the gain to the sweet spot, at which the system reacts as precise and stable as possible without creating any negative effects.
Cyclic feed forward
This part mixes some amount of stick input directly to the servos, bypassing the control loop. If correctly adjusted, the feed forward relieves the control loop so it will work more efficiently by only having to make residual corrections. Factory setting of the dial is horizontal which provides a good setup in most cases. Turn dial 2 clockwise to increase the cyclic feed forward. This will cause more cyclic stick input going directly to aileron and elevator on the swashplate. Decreasing the direct stick feed forward will do the opposite.
In case the cyclic feed forward is set too high, the stick input will over control the cyclic input from the control loop. Eventually the control loop needs then to steer back and compensate the unwanted cyclic movement. Even though you get the impression to have a more direct and immediate control over the servos with high feed forward values, unwanted side effects may appear, like pitching back on cyclic stops and imprecise fast forward flight.
If the direct cyclic feed forward is too low, the helicopter will feel softer, slower and less "connected". The optimal point depends of many factors like blades, servos, head speed, size and mass of the helicopter. Ideally you can increase the feed forward just as high as possible without any negative effects happening. So you get a quite natural stick feeling and the control loop is supported as good as possible. Before adjusting the cyclic feed forward you should try to find the optimal maximum cyclic gain first (see above). Then adjust the cyclic feed forward and after that, you may have to adjust the cyclic gain once again, as both parameters interact to each other.
The cyclic feed forward does not affect the maximum rate of rotation! If the helicopter turns too slow, you should check the settings of the swashplate limiter in Setup menu point L, change the control behavior at Parameter menu point B or increase the servo travels or “Dual Rate“ setup of your transmitter.
Also to get a quicker and more aggressive response, change the control style at Parameter menu point B (reducing expo and increasing the maximum rotation rate) and increase the cyclic response at Parameter menu point G. It is not recommended to increase the feed forward in this case! Although it may produce a quicker servo movement and more direct stick feel at first glance, you will get negative effects on overall performance as described above.
Adjustment at the device
The gyro gain and gyro operation mode can be directly adjusted from the transmitter. The other parameters mentioned above can be set by turning the dials on the device into a specific position. To adjust the dials please only use the supplied plastic BEASTX adjustment tool to prevent damage to the dials!
Gyro gain and operation mode
The tail gyro gain is adjusted by one of the transmitter‘s auxiliary channels. The more servo throw this channel produces, the higher the tail gyro gain will be. Additionally, the direction of servo throw determines whether the gyro operates in Normal-Rate mode or in HeadingLock mode.
While adjusting the gain or after initialization sequence was finished, the current amount of gain is displayed by one of the menu LEDs for about 10 seconds: When the gain channel is centered, this will correspond to 0% gain indicated by LED A. The maximum adjustable tail gain is 100% and will correspond to LED N.
The color of the Status-LED indicates the selected mode: Purple indicates Normal-Rate mode and blue indicates HeadingLock mode.
|Gyro mode||Normal-Rate mode||HeadingLock mode|
Please note that the actual percentage and sign of servo throw in the transmitter will depend on its brand and/or type! For the first flight we suggest to start with medium gain not higher than LED G (LED D for 450 size helicopters and smaller) in HeadingLock mode (Status LED blue).
- Operation without using the auxiliary channel for tail gyro gain is not possible!
- When gain is close to point A (0% gain) the rudder servo will not perform full servo travel as the gyro is switched off. Do not attempt to fly in this condition!
Dial 3: Tail gyro response
Factory setting of the dial 3 is horizontal which provides a good setup in most cases. Turn dial 3 clockwise to increase the tail gyro response. Turning dial 3 counter clockwise will decrease it. Increasing the gyro response will cause a harder stop and quicker response to rudder stick inputs.
Dial 1: Cyclic gain
The swash gyro gain (cyclic gain) can be set by dial 1 from 50% up to 150%. The factory setting is horizontal which corresponds to 100% swashplate gain. Turn dial 1 clockwise to increase the gain and counter clockwise to decrease. For your first flights we suggest not changing this setting. However, when using very small helicopters (such as 250 or 450 size), reduce the cyclic gain by 3 marks (=75% gain) as with such small helicopters the control loop tends to overcompensate more easily.
Dial 2: Cyclic feed forward
Factory setting of dial 2 is horizontal which provides a good setup in most cases. Turn dial 2 clockwise to increase the cyclic feed forward. This will cause more cyclic stick input going directly to aileron and elevator on the swashplate. Decreasing the direct stick feed forward will do the opposite.
Setup with StudioX
When you're using the optional available PRO EDITION firmware in combination with the Bank Switch feature you can set the parameters for the tail gyro and cyclic control loop in the StudioX app independent for all three flight modes. The dials on the device have no effect in this case. The auxiliary channel for adjusting the gyro gain is used to switch between banks (flight modes) instead of adjusting the gyro gain (see the page Bank Switching for more detailed information).