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Radio System FAQ
I am setting up a twin engined-model and want to be able to command the engines separately at certain times. Specifically, I always want the engines to respond only to the throttle stick (never any knobs or other items), and I want the left engine to operate alone if the C switch is in the up position with the right engine at idle; the left and right engines operating together in the C center position, and the right engine to operate alone in the C down position, with the left engine at idle. Can I do this?
Absolutely! But first a question we need to answer. How many channels is your receiver? Please see below, option I for 8+ channel receivers; option II for 7 channel receivers.
NOTE: that your knobs for channels 7 and 8 will still affect these 2 engines unless you deactivate the knobs. To do so, mix channel 7 to channel 7, -100% each side, link off, trim off, offset 0, switch NULL. Also mix channel 8 to channel 8 the same way. If using an 8U (non super) you will not have enough mixes available to do this. You can use your final free mix to turn off one knob, but the other must be set and not bumped during flight.
I. 8 channel receiver: this is fairly easy but a little complicated.
A. Plug your throttle servos into channels 7 and 8.
B. Do a pmix from throttle to channel 7 (the left engine) at +100 on both sides, trim on, no offset, link off, active on switch C up/ctr positions.
*If using an 8U (non super) you will need to duplicate this mix, with the first mix being active in up position and the second being in the center position.
C. Do a pmix from throttle to channel 8 (the right engine) at +100 on bothsides, trim on, no offset, link off, active on switch C ctr/down positions. (for step by step instructions on setting up the pmix, see below section II A.)
*If using an 8U (non super) you will need to duplicate this mix, with the first mix being active in center position and the second being in the down position.
NOTE: that your knobs for channels 7 and 8 will still affect these 2 engines unless you deactivate the knobs. To do so, mix channel 7 to channel 7, -100% each side, link off, trim off, offset 0, switch NULL. Also mix channel 8 to channel 8 the same way. If using an 8U (non super) you will not have enough mixes available to do this. You can use your final free mix to turn off one knob, but the other must be set and not bumped during flight.
NOTE: Throttle cut will not operate in this configuration. You would need to use a mix to set up a manual throttle cut:
| ___ | Press 2 advanced menu keys |
| ___ | Page up or down to an open mix |
| ___ | Press + to activate mix |
| ___ | Arrow over |
| ___ | Set master as OFS |
| ___ | Arrow over |
| ___ | Set slave as THR |
| ___ | Arrow over |
| ___ | Set % to a negative percent sufficient to shut the engine down (you'll need to experiment) |
| ___ | Arrow over to link and set link ON |
| ___ | Arrow over to switch selection and choose your desired throttle cut switch |
| ___ | Arrow over to switch position and set your desired position |
II. The easiest approach to doing this with a 7 channel receiver we can offer you to do this utilizes 5 of your seven available pmixes.
Left engine throttle servo plugged into channel 3
Right engine throttle servo plugged into channel 7
A. Create a pmix mixing thr to 7, 100%, switch c positions center and down:
*If using an 8U (non super) you will need to duplicate this mix, with the first mix being active in center position and the second being in the down position.
| ___ | Press 2 advanced menu keys |
| ___ | Page up or down to an open pmix |
| ___ | Press + to activate mix |
| ___ | Arrow over |
| ___ | Press + until first box says throttle |
| ___ | Arrow over |
| ___ | Press + until second box says ch 7 |
| ___ | Arrow over |
| ___ | Pull throttle down and press + key until right # says 100% |
| ___ | Push throttle up and then press + key until # says 100% |
| ___ | Arrow over leave link OFF |
| ___ | Arrow over and turn trim on (press + key) |
| ___ | Arrow over leave offset 50% |
| ___ | Arrow over to switch assignment |
| ___ | Press + until says SW-C |
| ___ | Arrow over |
| ___ | Press + key until says CNTR/DWN |
B. Left throttle operates properly on the throttle stick already with no changes needed, so that is the up switch position for the channel 3 servo. However, the channel 7 servo needs to be brought to idle, or kill, or however you want it set up. I'll assume you want it to idle. To do so, offset mix channel 7:
Select a blank pmix, make it active, and select the first choice as OFS and second as ch7. Make the percent 50% (you may need to adjust this to match your engine and your desired result), link off, switch C up.
C. Now, we need to operate the channel 7 throttle but not the channel 3 throttle when we move the throttle stick while in the down position. To do so, we do a pmix of throttle to throttle, -100% each direction, link off, trim off, offset 50%, switch C down.
Now channel 7 operates, but channel 3 returns to neutral, not idle position. Again, like we did in part 2, do an offset mix to solve this problem. Select an available pmix, make it active, OFS to THR, 50% (adjust as needed), link off, switch C down.
D. Lastly, we need to turn off the channel 7 knob to avoid its position affecting your right engine, so pmix channel 7 to channel 7 -100% each direction, no link, 0 offset, no trim, and leave the switch setting as NULL.
NOTE: Throttle cut will not operate in this configuration. You would need to use a mix to set up a manual throttle cut:
| ___ | Press 2 advanced menu keys |
| ___ | Page up or down to p-mix 6 |
| ___ | Press + to activate mix |
| ___ | Arrow over |
| ___ | Set master as THR |
| ___ | Arrow over |
| ___ | Set slave as THR |
| ___ | Arrow over pos 5 (pos 1-4 are left at 0%) |
| ___ | Set % to a negative percent sufficient to shut the engine down (you'll need to experiment) |
| ___ | Arrow over to link and set link ON |
| ___ | Arrow over to switch selection and choose your desired throttle cut switch |
| ___ | Arrow over to switch position and set your desired position |
*If using an 8U (non-super) you will not have enough mixes to complete this step. You will need to position the knob properly and be sure not to disturb it.
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