Throttle Cut with Safety Arming
There are plenty of methods of cutting a throttle on the Taranis, the most simple being a Special Function which sets the throttle channel to -100 when a switch is in a certain position. That’s all well and good, but what if the switched is accidentally knocked and the throttle arms again!? This method adds the safety net of the throttle output needing to be a 0 before it can be armed.
Setting up the functionality
Do not do this step if you are using a cleanflight based flight controller and want to use the OSD menu. The first step to creating this throttle cut is to create a Curve for the disabled throttle. This could, again, be done with a Special Function setting the throttle to -100, but using a Curve and Inputs shows what’s happening better, rather than being a random Special Function.
This is a simple 2 point curve with both Y at X and Y at X set to -100. I named the curve Cut.
The next step is to create some Logical Switches which take care of the actual enabling and disabling of the throttle.
L01 constantly checks the position of the throttle stick. The switch will only become active when the throttle position is between -100 and -98.
L02 will only become and remain active if switch SF is in the ↑ position and either L01 or L02 (this logical switch) is active.
Do not do this step if you are using a cleanflight based flight controller and want to use the OSD menu. The final step is to set the throttle Inputs. First, we duplicate the Throttle Input by right clicking and selecting duplicate. Next we modify the original input so that it’s only active if L02 is active. Double click on the input to edit it (see left image). Now we need to edit the the new throttle input so that it activates when L02 is not active, and routes the throttle signal through our throttle cut curve (see right image).
That’s the functional side complete. You will now not be able to arm until the throttle gimble is down. If you’re flying a line of sight aircraft with just a basic receiver/servo set-up, you’re all done. However, if you’re using a flight controller, there’s one more step you need to complete.
Making the throttle cut work correctly with Flight Controllers
In flight controller firmware, like Betaflight or iNav, you will assign a channel from the receiver to a Mode that tells the flight controller that it’s safe to arm. Historically, you’d set that up by adding a switch in a channel mixer on the Taranis, then programming the firmware to arm or disarm on that switch, as below.
The problem with this is that it can now be out of sync with the actual arm state of the transmitter. For example, you have the throttle half way up and flick the arm switch; the transmitter will not be armed, but the flight controller sees the different position of the switch and arms. However, it’s an easy thing to remedy. Simply edit the mix and change the Source from the switch, SF in this case, to our Logical Switch L02. The flight controller will now only arm when the transmitter has said it is safe to arm.
A final thing that can be added is audible confirmation of the throttle cut status using Special Functions. I custom made some “Throttle Armed” and “Throttle Disarmed” tracks, and set them up like this.