Traditional Heli Minimum RC Requirements

Hello all
As I am new in this ardupilot world so first let me introduce myselve. This is my first posting.
I am a retired german electronic engineer. English is not my favorit language so I will make several mistakes but I hope you will understand the meanings of my postings.
For really very long time I us RC-Systems mainly Futaba to controll my vehicles, cars, boats, planes and helicopter. All is running fine. But for a future project in my mind I am now looking for a more sophisticated flight controller and so I reached this wonderful platform.
To learn more about flight controller I want first to upgrade my T-REX 250 Flybar System helicopter with an first ardupilot based flight controller. Out of the list the the MATEKSYS H743 MINI is my first idea for this relative small helicopter.
At this time the helicoper is controlled by a max 6 channel RC Transmitter Receiver combination. 4 channels are normal PWM channels used for Collective Pitch; Tail Rotor; Cyclic Pitch, Cyclic Roll. Channel 5 is switching the Tail Gyro between normal and Headlock mode, Channel 6 switch the motor on off. The motor is controlled by a simple govenor motor driver with soft ramp up.
So what I want is to use in first learning step to use the flight controller instead of the gyro in a moreless comparable mode like above. I think this is wath you call Stabized Mode.
So now I have read in the wiki a minimum 8 channel RC System is needed: (elevator, aileron, collective pitch, rudder, flight mode, tuning knob, auxiliary function switch, throttle hold).
The first four are identicall to my normal functions. Flight mode is similar to my Tail Gyro switching. throttle hold is similar to my motor switch. But is the tuning knob and auxiliary function switch really necessary. What are these functions for?
Second I have read that the throttle hold is using by default channel 8. Is it possile to switch thiis to another channel (e.g. channel 6 )
Is it possible to use the helicopter only in one Mode like stabilized mode or is a switching during flight to any other mode necessarry.
I look forward for your replies
Best regards

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Hi Juergen welcome to ardupilot community its nice to see more people taking intrest in traditional heli stuff. Ok so the flight controller u already have is very good and beyond that u need a gps ideally an m8n or better i would say go with fly woo goku v3 m10 gps good for small helis and also u definitely need minimum of 8 channel radio u can definitely go for more and also u may need a ubec of 5 volts depending on wiring and yeah also a sd card is needed for logging the data and to check the logs for tunning purposes

Hi goobisoft, thanks for your reply.
As I understood GPS is a nice option, I love GPS for a really long time since the late 70th. But I don’t see wy it would be necessary for my first steps. I still want to controll the heli manually as before only instead of a traditionall stabilizer from the RC-model market with an ardupilot compatible platform. So I think the actual position information is not necessary for this step.
A 5V BEC is implemented in my existing motorcontroller.
But now to the main question, the number of channels. If it is so as you and the wiki say I also have to buy new transmitter / receiver combination which was not planed with my budget. I still believe you but I like technical to understand such things. So again what are the reason for the extra channels. With normal RC equipment I am able to controll the heli with just 4 servo and 1 switch.
Best recards

As u said u u dont need gps for the moment i was asking gps because u need it to go with the autopilot i order to fly in gps modes such as pos hold, return to launch, circle modes etc. But i f u want to only fly in stablize or acro mode for now u can totally avoid gps for now and also can use 6 channel radio as of now but if u want to switch modes during flight then u need more then 6 channel

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Right now i m also working eith matek h743 mini board its a fantastic little board especially for small aircraft great choice right there

Again thanks goobisoft, yes in the first step I only want to fly in Stabilized Mode just to learn the ardupilot approach and compare it to the traditional technique.

Ok u can go ahead without the gps and make sure u have sbus capable radio or atleast ppm maybe and ask anything u need to know and i recommend u to read the ardupilot wiki couple of times atleast

Of course SBUS is clearly a must and available. Also I try to go through all availabe information. :grinning:

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@Juergen-Fahlbusch just want to make one correction to the information given here. A minimum of 6 channels for an RC radio is needed for traditional helicopters. That would include a channel for flight modes.
The channels would be
Motor interlock (throttle hold)
Flight Mode

As @goobisoft says, the wiki is a good source of information.


Hi Bill, also thank you for your reply and confirmation that at least a 6 channel RC will work.
I am noticed the ardupilot project just I week ago. I am reading many but really not all in deep. Mainly I am focusing on traditional helicopter.
So on my RC system channel 5 and 6 only two way switch. For motor interlock I assume it is ok. But what is minimum needed for Flight Mode. From my momentary understandig I only want to use Stabilized Mode. What else is needed or recommended.
Best regards and nice saturday

Well the channel 5 in ardupilot is dedicated for flight modes I don’t think u can change that so for motor interlock u have to use channel 6 and then for arming u have use rudder method but I don’t recommend rudder method as arming disarming for helicopters

@goobisoft makes a good point that if you want to have arm/disarm on a switch then you would need more than 6 but I use rudder arm/disarm all of the time. It scares me a little to put arm/disarm on a switch because if you accidentally hit it then you will lose some of the stabilization as you are performing an autorotation because disarming will also turn off the motor.

@Juergen-Fahlbusch a 2 position switch is fine for motor interlock. You probably want to use the logic in your controller to be able to use 2 switches (3 position switch and 2 position switch) to get 6 different outputs for channel 5 (flight modes). This allows you to take advantage of the 6 flight modes that you can program into the controller. They are set by having separate PWM ranges for each of the modes.

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@goobisoft, the sequence of channels is not so important, so I am able to set the motor interlock to channel 5 and flight mode to channel 6.
@bnsgeyer Bill I am not able with the existing system to use other than a single on/off switch on channel 6 so I will have only two flight modes for the first steps without using a new transmitter.
So for my background understanding, is it possible to run a traditional helicopter just from the beginning to the end in only one mode like the Stabilized Mode or is it necessary for any reason to switch to another mode during operation / flight.
And also this arm / disarm feature. Is it necessary do arm or better to disarm the controller for any reason during flight. What does disarming mean, all controlles of the flight controller will be switched off and the signals from the receiver are directly routed to the servos?
My experience with this small helicopter shows that a controlled autorotation landing will not really work.
I think I have to read more and more of all your wikis :grinning:

@Juergen-Fahlbusch yes you can set the flight mode to channel 6 but you will have to make a change to the parameter FLTMODE_CH. I would suggest the following two modes for your switch: stabilize and altitude hold

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Hey Bill, this sounds good and let me feel to look deeper to ardupilot as my next project.
Thanks a lot

There is arm/motor emergency stop 3pos switch that reduces inflight disarm risk by doing motor stop instead of disarming the vehicle instantly so it will disarm only after few seconds have passed.

  • High - try to arm
  • mid - MES run
  • low - MES stop

Disarming in flight is undesirable. Using sticks for disarming is quite common and works well.

Operational vehicle can be flown in one mode, you need at least 2 for tuning (you can use switch for auto tune but you still need a channel for that). It is good to have emergency mode switch so you can go to lower automation mode if autopilot acts up in higher automation mode. Ex: Loiter to Stabilize.

Hi @LupusTheCanine and thanks for your reply.
What do you men with the 3 pos switch. Is it a switch on the transmitter or on board of the Helicopter.
My at the moment prefered and existing transmitter don’t have such switch. Only two 2 pos switches are available one on channel 5 and one on channel 6.
From @bnsgeyer and @goobisoft I have learned on channel 5 the Flight Mode with Stabilized Mode and Altitude Hold Mode will be fine for the beginning. On channel 6 the Motor Interlock (in my understanding Motor on / off) would be fine.
So what is the arming / disarming feature for. As I understand from the wikis arming is necessary for flying in non manual modes which will be not my case for the beginning.
Best regards

Yes, 3pos switch is one switch with three positions on the radio. Though nothing stops you from using a dial or a slider as one as Ardupilot only cares about signal values on the assigned channel.