How To Program Differential Thrust

by FliteTest | July 12, 2016 | (5 Ratings) Posted in How To

In this episode, Josh shows us how to program a 6 channel transmitter for differential thrust. Differential thrust is used for twin engine planes to give better yaw authority. 

We programmed the Graupner MZ-12, which is a versatile and easy-to-use programmable transmitter. 

To program differential thrust, you’ll need a 6 channel receiver and a 6 channel transmitter with at least four mixes. 

On the GR-12L reciever Plug the left motor into channel 5 on your receiver and the right motor into channel 6. Do not plug anything into your throttle channel.

Make sure you remove your props before setting or testing and electronics!

On your transmitter, go to free mix. 

Inside the free mix tab, program Mix 1 to potentiometer (throttle) for channel 5. Go down to Mix 2 and select potentiometer (throttle) for channel 6. 

Set Mix 3 to rudder for channel 5, and move over one section to the right to assign the rudder to a switch. Press enter and push the desired switch to “On." 

Set Mix 4 to rudder for channel 6, and move over one section to the right to assign the rudder to a switch. Press enter and push the same switch used in Mix 3 to “On.”

When you flip the switch on/off, you should see the on/off position for both Mix 3 and Mix 4 change simultaneously on the transmitter screen. If it’s backwards, reprogram it with the switch in the correct position. Both switches need to be programmed so they turn on/off simultaneously.

Go back to Mix 1 and scroll over to the verse/travel adjustment. Go to travel and change it to positive 100%. Press enter to save. This will allow channels 1 and 5 to operate under the same parameters.

Scroll down to Mix 2 and repeat the exact same process, so that channels 1, 5 and 6 are all using the same parameters and move together.

Program the travel for Mix 3 to negative 100%. If the transmitter says that the mix is off, flip the switch you program to the opposite position, and you will be able to program the travel.

Program the travel for Mix 4 to positive 100%. When you increase the throttle, 1, 5 and 6 should move in the same direction simultaneously. 

5 and 6 will move opposite of each other, this is the best visualization of differential thrust.

Hook up your motors to test it out, make adjustments as necessary, and you’re ready to fly!








hotroder69 on July 13, 2016
Thanks Josh, this video is a huge help. I love twin motor planes.
Charlie Spann
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joshk20000 on July 13, 2016
thanks so much! was just trying to figure this out for my mini cruiser and it's so much easier with this video!
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jksbusiness on July 13, 2016
Thank you for showing a close up of the transmitter while talking through the settings for flight. It is difficult, as a beginner, to connect with a local flight instructor. Every tutorial that shows a step by step process is essential. Thank you for offering this exact transmitter in the Flite Test store. More vids like this, please!
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kb0bnz on July 14, 2016
Thankyou I have needed this for a very long time. again thanks

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bensgreentrain on July 13, 2016
thanks for the info. I started the Sea Duck this AM. Now I think I'll redo my "A" tail Bronco so that I can fly with differential thrust.By the way, the Bronco is a great flying airplane. Please keep up the good work.

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Sirglider on July 14, 2016
Educational but commercial oriented article. I am disappointed that the solution provided is always on brands oriented. Why not on open source firmware? If you want to make this hobby affordable for all, try to show solutions on cheaper solutions like 9x, 9xr or even taranis radios.
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FoamTest on July 30, 2016
I used this article to program differential thrust on my spektrum Dx8
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pressalltheknobs on July 19, 2016
I wrote a blog entry on on how to setup differential thrust on a FlySky/Turnigy i6

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Extreme Air Pilot on July 19, 2016
Hey Josh, Very helpful. I really like twin engine planes.
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eric75 on July 19, 2016
This bothered me a little to tie up four channels to control two ESCs, and I haven't even built a twin...yet. On my Spektrum DX6 I was able to mix 100% throttle into rudder, then added another mix to put -100% of rudder back into throttle. It seems to work the same as what you did here except that left motor uses the throttle channel and right uses rudder channel. If rudder authority is excessive, I can trim back the range on the rudder channel over in the "servo setup" menu, but there may not be as many other options for fine tuning. Am I missing anything?
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pressalltheknobs on July 20, 2016
Well you don't have a rudder anymore!...That might be ok if you don't Otherwise you need the rud channel and a 2nd motor channel. The usual solution is to mix Thr to Mtr2 and then rud 100 to Thr and -100 to Mtr2 ...adjust the sign as necessary and Rud weight as desired.

Since the Rud channel is your second motor channel I don't think you will want to mess with the Rud servo extents or your model will just fly in circles. I think you can just adjust the weight of Thr in the first mix and Rud in the second to tone down the effect. That's another disadvantage because you have two rates on different controls to adjust. Often Thr doesn't have a Rates switch to match the Rud. If Rud is the master to the two throttle CHs as in the "usual" solution then you can use the Rud rate switch to control both.

Some TXs have restrictions on what mixes are allowed with Thr. I don't think you can mix Rud->Thr on the DX6i for example, and since it only has 2 free mixes you can only do 1/2 diff (ie have the rudder affect one motor)

Not sure why the Thr CH is "moved" to CH5 for the Graupner. Probably there are some restrictions or behaviors on the normal Thr channel that are inconvenient.
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Kick_A_Puppy on July 23, 2016
Can I gut my Delta Ray and use the parts in a FT scratch build? I also have an old champ that I would like to try and use the components for a build. Any suggestions?
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FoamTest on July 30, 2016
I actually just designed a model to use champ electronics here is the YouTube video link.

I posted an article on it but I am awaiting approval.
I don't have digital plans for it yet but the center section of the wing is a 8" by 3 1/8" and the wingtips are 4" by 3 1/8". The horizontal stabilizer is 2" by 5". Finally the fuse length is 10". You can experiment with fuse designs, but if you watch the video it will give you a basic design of the fuse I used and had success with.
I have only made glider versions so far and I can't wait to make a powered version, if you do post a video of it on youtube. I'd love to see it!
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FoamTest on July 30, 2016
Thanks so much Josh I just got a full size guinea pig and now I can do flat spins :)
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m_eye_flying on October 16, 2016
I have the FlySky FS-TH9X transmitter set up for DT using program mix and it works, my only question I have is , I was using two 30AMP ESCs in Y setup with A2212/13T 1000KV motors, but today, 1 day after getting the DT to work, one of the ESCs smoked and fried a motor along with it. I had heard it was OK and it was not OK to leave both + cables connected on the ESC connector going into the RX. This happened right after I used the TX to calibrate both motors at once. Was that the 'smoking gun' no punt intended or could it have been because both ESCs were connected with both + intact? These ESCs are SimonK 30AMP with BECs. Thanks.
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msbealo on February 17, 2017
Thanks for that. Really appreciated. I'm now closer to being able to test my dual motor 3D printed (transparent) boat (now with differential thrust!).
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