Headspeed governor

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What is this and what does it?

Using the governor function you can simply preset your head speed with the transmitter, i.e. when you like to fly your heli with 2500rpm, you set your throttle curve in idle 1 to straight 62.5% in the TX. Then you just place your heli on the flight field, switch to Idle1 and it'll autonomously will spool up the rotor rpm to 2500rpm. Then you can take off and fly and you will get 2500rpm all over the flight, no matter what load condition the battery is or if your nitro motor will run lean. The governor will try to hold these 2500rpm as good as possible. When rotor head load increases, it'll increase throttle as necessary, when you unload the head and the head speed increases due to aerodynamic force, it'll decrease the throttle automatically. Typically this is a lot better than only controlling the motor with static curves made in the transmitter. And next time, again you will get those 2500rpm when flying the next battery/fuel tank, although this battery might be old and voltage is slightly different or the nitro motor may run more rich or lean.

For electric helicopters the governor function is a good thing if you use an ESC with bad head speed governing capability. Most (cheap) ESCs do not have a very good governor or don't feature any governor function at all. For example with some ESC you may get tail pumping at some specific rpm ranges or very abrupt throttle inputs when the load on the rotor head changes. Here you can get good results with the BEASTX governor as besides observing the motor rpm/head speed this will allow to give direct throttle input to cyclic/collective stick input. So it always will be one step ahead compared to a traditional governor function. Using a high priced ESC on the other hand, these typically have so good governor algorithms that it doesn't make any sense to use an external governor and the ESC has knowledge of what the motor is doing at the moment and what's the momentary current, voltage, etc. So here the BEASTX governor function probably will not give any performance boost.

So if you are not afraid of the additional wiring and setup procedure using the RPM governor of AR7210BX can make your heli and your ESC get a very consistent head speed governing at minimum effort. Of course if you think your ESC is working OK and that the governing is working to your satisfaction there is no need to use the governor feature.

Especially for the nitro helicopters using the governor functionality of the AR7210BX can be very handy as the unit necessary for this is already mounted to your heli. There is no need for an extra device. Just connect a rpm sensor of your choice to the unit and after performing the governor setup procedure you will not have to adjust complicated throttle curves anymore. Just choose the desired head speed you want to fly with and set it up in the transmitter, AR7210BX will do the rest including soft start and autorotation bail out feature.

Is the RPM Governor function also available for AR7200BX / AR7300BX?

For the SPEKTRUM AR7200BX / AR7300BX there is a firmware with nitro governor functionality available (Version 4.0.14) which you can get for free by updating with the StudioX software. For electric helis there is no governor available.

Nitro Governor - When enabling the governor or when recovering from an autorotation the throttle increases up to full throttle and stays there

  • Nitro helicopters react very sluggish during when initially opening the throttle. Especially when the clutch is worn out it can take a lot of time until the rotor gains head speed while the motor already runs at full speed, trying to spool up the rotor. Now when measuring the motor speed at the clutch, the governor will open throttle and stay at full speed as it detects the desired speed seems to be faster than the helicopter allows. So you need to prevent the throttle from opening too fast during spool up by decreasing the spool up rate (PARAMETER MENU point J) or quick change rate (PARAMETER MENU point K).
  • Make sure the headspeed is set correctly in the radio and is not higher than the helicopter is able to turn. Always keep enough space for the governor to govern, meaning the headspeed should always be equal or lower 80% of the maximum speed.
  • Check settings of gear ratio and signal divider. If these are not correct the system is not able to calculate the headspeed from the motor speed correctly. Especially when using a sensor with magnet pickup make sure to set the signal divider correctly to the amount of magnet triggers. Note that the magents usually are directional and only will trigger the sensor when they are mounted in correct orientation.

How to adjust Parameter menu point I ( Throttle response)

The setting of menu point I determines how fast and hard the system will open or close the throttle when the rotor speed changes. With ideal throttle response you get a very consistent rotor head speed. When loading and unloading the rotor disc, the head speed should recover quickly and definite but not hectic.

  • If throttle response is too low the main rotor may speed up immediately in unloaded conditions, e.g. when the helicopter is descending and the RPM Governor will only give soft throttle inputs when the head speed decreases.
  • If the response is set too high on the other hand, the throttle may stutter audible when unloading the motor and/or the motor rpm will kick in very hard and overshoot after the rotor head was loaded and the rpm decreased, causing the tail rotor to turn due to the immediate load change.

The height of throttle response highly depends on factors such as heli size (blade size), motor power and performance and/or the throttle response behavior of the speed controller (when flying an electric heli). If you need to adjust the throttle response, we recommend to start with the lowest value and increase accordingly. Also you should use a lower head speed for adjustment as here you can see the effect more distinct. Only increase the throttle response stepwise and make sure the throttle will not start to oscillate.

Warning.png Note that with nitro helicopters high throttle response can cause the motor to quit when the throttle is opened too fast. With electric helicopters changing the throttle very fast can cause the speed controller to overheat and especially hard changes from unloaded to loaded conditions can cause incorrect commutations of the ESC (depending on the type of motor) which can damage the ESC if this does not have appropriate protection mechanisms.