Add a Safety Throttle Lock

How do you make throttle-channel active for the whole flight only if throttle-stick is in it’s lowest position when throttle-cut switch is activated? This is interesting brain-exercise, I saw this on some forum not long ago and it’s been on my mind ever since. Now I tried to search it and did not find it anymore so I thought that maybe it was this way. If it was not, well, this works. With Jeti there’s usually several ways to do things.


We could use a simple AND to make it as “when throttle stick is -100 and throttle-cut is off” but then this would activate during flight every time throttle stick is in it’s lowest position. So, that does not work. We need to get fuzzy!

Fuzzy logic to rescue!

We need to think a bit fuzzy here for a while. What we need is a command like “Disable throttle-cut when throttle-cut switch is off and throttle stick is at it’s lowest position”. What we really need here is fuzzy to keep throttle-cut from jumping on and off during flight every time throttle-stick is in it’s lowest position. Since we are making a throttle-cut and not a simple throttle-off this has difference.

Turned out it is simple, done with only two logical switches!

How to make Throttle Cut with dual safety

First create a logical switch with name “Throttle”, then another with name “ThrottleCu” (for throttle-cut).

Settings for logical switch 1

Control 1 is your throttle stick, make it centralized and proportional:

Control 2 is your physical throttle-cut switch. Make it so it shows as ON when throttle cut is OFF (you’re flying):

Now we can make the rest of the settings to the Logical Switch. We want Control 1 to be active when throttle stick is in it’s lowest position. So make it as “X is less than -97%”. Condition is “Multi” as shown below. Control 2 is as it is.

NOTE: If you use your equipment if hot weather you might have a non-working safety switch! If this is the case you might need to put “X is less..” value to -96% or -95%! This is due changes in component-values in warmer temperatures.

You are done with first logical switch. Now, let’s make the other one.

Settings for logical switch 2

What we need in here is control 1 where we choose the logical switch 1 we just made, again, make it centralized and proportional:

Control 2 in this logical switch is again our physical throttle cut switch, make it exactly the same way as in control 1:

Again, it’s time to tie it all up. Since our logical switch 1 is a MULTI-switch it can be OFF, ZERO or ON. We want to use only the ON, so we make the Control 1 as “X is bigger than zero”. Condition is AND in this logical switch and control 2 is again just control 2, the physical switch.

You’re done!

Testing the function

Make sure your physical throttle-cut switch is on, meaning your throttle is cut. Center your throttle stick. Now your logical switch screen should look like this, both our logical switches are OFF:

Now, activate your physical throttle-cut switch like you were to activate throttle. Keep your throttle stick still in the middle, what you see is this:

As you can see the logical switch 1 is now in ZERO. It’s not yet ON because your throttle stick is not in it’s lowest position. That is also why our logical switch 2 is still OFF meaning your engine is not activated even when your physical throttle-cut is off. We need to lower the throttle stick to it’s lowest position to enable normal function, so, lower throttle stick to it’s lowest position and keep it there:

As you can see, now both logical switches are ON. If you now move your stick up and down to any position the logical switch 1 is either ZERO or ON and the logical switch 2 is kept in ON position, it never goes off until you activate your physical throttle-cut switch. After physical switch is used you need again move the throttle stick to it’s lowest position to enable the logical switch 2. Try it out!

Use in transmitters Throttle Cut

Let’s put this added safety to good use. You could activate a hold flight mode with this if you wanted but using it on actual throttle cut might be better. In that way you can test all your flight modes without having the risk of engine starting to run in mistake. (Always, always test your setup for these anyway!).

So head on to “Menu” -> “Advanced Properties” -> “Other Model Options” and scroll down to throttle cut:

For the throttle-cut switch select the logical switch 2, but reversed:

That’s it, your done!

Safety warning and disclaimer

Always make sure everything works as expected before actually flying your model. This is especially important on everything engine-related. RC-Thoughts or me personally are not in any way responsible for anything you do to yourself, your models or surroundings when using these how-to’s.

19 thoughts on “Add a Safety Throttle Lock

  1. Tero, great write up. I have been wanting this feature for as long as I can remember. I am new to Jeti and this article leaves out some details that may be obvious to a Jeti user. In your example, it appears you are using a three-position switch (SA) for throttle-hold. Is the use of a three-position switch mandatory or would I run into issues using any two-position switch?

    In the first screenshot while setting the logical switch for Control 1, your transmitter appears to be in the Throttle-Hold state from the looks of the indicator in the upper left hand window of the screen. Is this the case?

    For Control 2 — your physical throttle-cut switch. You state to "make it (SA-Switch) so it shows as ON when throttle cut is OFF (you’re flying)". This is a little confusing for me. To rephrase the SA-Switch can be in the Back, Middle or Forward position. For Control 2 can you confirm that the SA-Switch should be physically in the back position and shown as ON (Check) when setting up Control 2?

  2. It does not matter if the switch is 2- or 3-position. We are only interested in the ON-status of it. Don't mind the hold flight mode, I use a safety-switch for throttle and additional hold-switch.

    What comes to your question of control 2 and physical switch, maybe this helps, program it like this:

    Set your throttle cut switch on, meaning in the position where throttle is cut (motor can not run). Then go to the control 2 programming, go to the "add switch" screen and change status of throttle cut switch. It's now in right position.

    In Jeti-world there is no "back and front" positions of switches, they can be whatever user want's to them to be, that is one of the beautiful things with Jeti. And also one of the confusing things :)

  3. When using teacher mode, I'd like rescue switch to turn off the student control and leave it off until the student switch is cycled. I have a logic switch that only turns on student when rescue is off and student is on. But, upon releasing rescue the student becomes active again. I got around this by using a second logic switch that locks the student out for five seconds to allow me to turn student mode off after the rescue is complete.

    So, logic one says "student only when rescue off and student switch on
    Logic 2 says "student off for five seconds when rescue is activated
    Logic 3 says "student only activated when logic one and logic 2 allow it. This is the student switch in wireless modes/trainer.

    However, it would be better to just "latch" the student out until the student switch is recycled. Thoughts? Thanks.

      1. I'm using Spirit Pro with this heli, using a spring loaded switch G for rescue. The student switch is F not spring loaded (I always hated physically holding the switch so someone else could fly). DS-16 is the teacher, and DS-6 is the student. Dan

        1. This is tricky, the fact that the student-function is made by the same switch that is needed to reset it causes some thinking. Cool brain-teaser :)

  4. What keeps L2 enabled when the throttle stick is moved from idle? This should set L1 to 0 and so the first condition for L2 should be false?

    1. Since you have your throttle cut switch disabled and L1 is multi. The "0" is not "off", that's the beauty of "multi". Try ti!

      1. I have and it works! I was just trying to understand how when the switch is enabled and the throttle moved up from idle the first input for L2 is still enabled even though L1 output should then be at 0 and the first condition for L2 should be false

  5. I have the same question as Chris. I couldn't find a description of a Multi gate. What happens in the hardware? Some intermediate voltage that tells L2 not to change its state?

    1. Multi emulates 3-position switch, the beauty is that the 2 positions can be anything, in this case throttle stick and a physical switch. This is in manual too (DC-24 page 107)

  6. Got it. Just think of the "o" state as a high impedance open circuit so it acts like L1 isn't even connected to L2.

    It would be nice if Jeti built this brilliant logic into the Throttle Cut function so we would't have to create it for every new model.

  7. Being new to Jetti I've followed the instructions to the best of my ability, understanding where we are going but failed miserably every time. The screen shots look like an older software version, is there any likelyhood of it being re-written to 5.03 in the future?

    1. There is no straight reason to rewrite, all the options are in the newer firmware too. The direction of settings in important, check if you have some positions inverted or not being proportional etc.

  8. If you have sound on events, "throttle lock" on the throttle lock switch and "motor active" on logical switch L2, then you can set a third message "set the throttle to zero" if you turn the throttle lock switch off and your throttle is not at zero. For this you need a third logical switch, L3, call it something like "Tcut warn". This is L1 reversed AND the throttle cut switch in the motor run position, i.e. the switch input shows a tick when the motor should be running. L3 is then used to activate the sound file with the "Set throttle to zero" warning in.

    This works because if you turn throttle lock off with the throttle at zero, L2 reversed turns off so L3 does not meet the AND criteria. If you turn throttle lock off with the throttle above 0%, L2 reversed remains on L3 is activated and you get the warning. When you reset the throttle to zero L2 reversed turns off and stays there so you never get the warning again. It is essentially a slight rework of the L2 latching switch to stop you getting the warning again.

    1. ERROR in the above note. It should read that L3 uses L2 and the throttle lock switch. The second para was correct.See below

      For this you need a third logical switch, L3, call it something like "Tcut warn". This is L2 reversed AND the throttle cut switch in the motor run position.

      1. Hi all
        you don't need a third logical switch. (at least not on a dc16 gen1)
        if you assign the warning.wav to your physical throttle-cut switch (i.e. Sa)
        in the on position, it plays that message when the throttle is not -100.(-96)
        If the throttle is -100, then the message for throttle active plays, and the warning will not play.

        so in sounds on event you will have the following lines:

        switch file delay repeat
        L2 X esc.wav 0.0 no
        L2 V t-cut.wav 0.0 no
        Sa X warning.wav 0.0 no
        (Sa in off position)

        ps dont uses delays or repeats for the warning :)

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