DX8 to Orange 9ch Rx to APM 2.6

I am having trouble with hooking things up.

The doc says straight connections 1-1,2-2, etc from the Rx to the APM.

Does that mean every manufacturer maps their functions exactly the same? That seems unlikely but I have never used anything but Spektrum.

When I do that my DX8 does not cause the correct indications in the Mission Planner radio setup. Not even close. I think APM yaw matches the rudder on my radio, others are mixed up.

I was able to get correct servos working correctly following a DIYDrones post that mapped
1 - 3
2 - 1
3 - 2
rest straight through

The issue then became the only way to get motor movement was to Y the Rx pin 1 to both APM 3 and direct to the heli ESC.

Pin 1 becoming both throttle and collective so having different throttle and pitch curves is a puzzle.

How can a radio running in airplane mode have both throttle and collective when airplanes have no collective - Sorry it that’s a dumb question, I am feeling pretty dumb right now.
I have only ever flown helis so am unfamiliar with running a DX8 in aircraft mode.

Any insight would be appreciated.

Forget Throttle curve. In the DX8-plane (Acro) mode that is now your pitch curve even the name throttle stays.
Your Rx Throttle connects to your APM input channel 3 as you did. But your ESC connects to APM output channel 8. You will from now on run your Helli with governor at a fixed RPM. There are options for the motor fixed settings in the APM settings. I am using ESC governor. See the APM manual.
Use your Hold switch (top right) for switching your motor on after arming.
If your DX8 is Mode2 than your left throttle stick or from now on your collective pitch stick should be in the 50% position where your blades should have 0 pitch.
Good luck!

Thanks Fred.

Rob, Spektrum really is the odd-man out here. It’s a really sad combination of not following standards, not being flexible, and not documenting how their system works. I actually can’t help you much as I do not understand what Spektrum is doing. They have attempted to make things easy for users, by being very inflexible on their setup. But in this case, it makes it very difficult.

Thanks guys,

I rewired as above and all the servos work correctly.
Unfortunately I don’t have a governor on this old test heli.

I have

  • my Mix (throttle hold) switch toggling Aux3 (APM input Ch8)
  • set H_RSC_MODE =1 with various setpoint values

The APM arms ok, but no joy getting the motor to spin with the ecs connected to APM output Ch8.

Is a governor mandatory for APM on a traditional heli?

I sort of thought from the wiki that mode 1 would put out a constant throttle value but perhaps I am reading too much into it.

I have never connected without a by me programmed ESC - governor. I don’t know the answer. But important is - after dedicating a new switch you must let the APM 2.6 know with a new Radio calibration.
I hope this helps.

Finally got her flying.

Main trick was to go back to Heli mode on my radio.

Wiring like this…

Rx -> APM
1 (throttle) -> ESC (no connection to APM)
2 (aileron) -> 1
3 (elevator) -> 2
4 (rudder) -> 4
5 -> 5
6 (aux1=pitch) -> 3 and 8

I can now set throttle curve and hold in my radio.

Another challenge is to get the APM to arm.
I need to have the pitch in the basement. I normally fly with a fairly shallow pitch curve but the APM wont arm unless the negative pitch is bottomed out. I have one radio flight mode set with a linear pitch curve and use that to arm, then switch a flight mode with a shallower curve to fly.

I tried Ch8 passthrough (H_RSC_MODE 1) but could not get the APM to spin the motor. It is running in mode 0 now.

Stability mode with all default APM settings is really quite stable. I am getting tail drift so I will need start playing with config settings I guess.

I was pleasantly surprised as the heli previously was tuned, and flying great, on a beastx.
The APM, at least in hover, is comparable out of the box.


I totally disagree with using HELI mode and putting your throttle directly to the ESC. Ask yourself this question. If you are in flight and you turn off your radio , what’s going to happen??

David R. Boulanger

[quote] If you are in flight and you turn off your radio , what’s going to happen??[/quote]I have been flying helis for a few years now and have never turned off my radio as I was flying - it seems like a far fetched scenario. I am more troubled by the idea of the heli flying on its own without my ability to kill it.

The APM 2.6 is capable of a lot. I assume you have a gps unit on it. If your Heli had an issue receiving the signal from the transmitter would it not be better to fly home rather than to drop out of the sky? I did not really mean that one would turn off their transmitter by accident. I just think there is a better way for your set up. I also think that the APM needs to be “aware” of everything that’s going on with the aircraft.
David R. Boulanger

Robs 133,
I realize I am not making a friend here but you never answered my question. What happens if you turn off your radio? Have you bench tested this? I run Spektrum stuff and I am concerned that your best case is the motor stops but the heli continues to try and fly. Depending on how your failsafes are it may just continue flying somewhere without a pilot because the APM has no idea that a problem exists.
David R. Boulanger

Hi Guys,
In reply to this Acro/Heli question this is what I did and it works just fine.
In looking thru the forum to find out what to do with ch3 and ch8 on my pixhawk, I found a post in which Rob_ L suggested creating a mix to control ch8 (this was my Ah Ha moment).
My Tx is a Dx8 and Rx is AR8000 with a 3dr ppm encoder to feed the pixhawk, on the Rx ch3 goes to thro. port and ch8 goes to Aux 3 port.
Then a mix is done in the Tx, Thro to Aux3 so Thro. on Tx now drives ch8 both move in same direction both move same amount… Here comes the tricky part.
Using servo travel limits on Tx thro. is -100%, +100% Aux3 is -100%,+100% and the CC esc goes to ch8 out on pixhawk with ch8 set to “pass thru” in mission planner.
HOWEVER the CC esc would not arm no matter what I did, The pixhawk would… just not the esc to start the motor.
I found out from a Castle Creations tech that the esc is looking for a high and low signal to arm and start the motor (another Ah Ha moment).
So with everything hooked up and plugged in and MP running I did this… on Tx cali screen in MP watch the ppm signal number for ch8, now on your Tx go to servo travel adjustment screen and scroll to Aux3 travel adj. - scroll down and click on the neg. number (number on left) watching the Tx cali screen increase that neg. number until you see 1000 ppm on radio cali. ch8 in MP (my neg. % was -130 to get 1000 ppm).
Then shut down everything and reboot, plug in the heli and the esc should now start the motor…
I did have to bump up the power the esc puts out to the motor to get the first initial spin going but that’s it…
This is all done in Acro mode on my Dx8 and it works beautifully!!
Thanks to Rob_L’s suggestion in a earlier post about a mix…
This reply has gotten longer than I intended, but I hope this helps you…
I understand what both you guys are saying about failsafe and turning off your Tx, its called setting up failsafe for loss of transmission and you test it by shutting off your Tx. (Very Scary the first time)
I have a qav400 quad with a pixhawk FC and have a RTL switch and the loss of tx. failsafes set up in it.
They both work flawlessly every time… and both still scare the crap out of me each time I test them, but she always comes home like a hungry cat…
Best of luck,