Throttle cut and throttle hold
Greg Gimlick
First of all, happy holidays to everyone! I hope everyone's holiday season is great and the new year brings you all the happiness and success you can handle. This month I'll finish the discussion started in June with the mention of programming throttle cut/hold for fixed-wing airplanes. Thanks to everyone who sent me explanations and photos.
Throttle Cut/Hold
A bit of definition might be in order, although as fixed-wing pilots, we tend to use these terms interchangeably.
Throttle hold is what it says. When selected, the radio will place the throttle setting to a preset value, regardless of throttle-stick position, and keep it there. This setting can be programmed to whatever throttle setting you wish, but activating the switch will always take it to that level.
Throttle cut is preprogrammed to always cut the throttle to zero (or below) and designed to kill the motor. Many radios have put this on a spring-loaded (momentary) switch, while throttle hold is generally on a two-position switch.
These were provided with helicopters in mind and most radios, until recently, did not provide such options for fixed-wing aircraft or sailplanes. In June, I showed my JR 9503 mix to assign a cut/hold function to a switch, thereby providing an extra measure of safety should I bump my throttle stick after the airplane is armed. This garnered much interest and response and I'm going to dedicate the rest of this column to showing those solutions.
For our purposes, we want a switch that will keep the motor from starting even if the ESC is armed. Whether you argue semantics or not, that switch will kill or hold the throttle in the off position.
Readers' Solutions
You people certainly came through on this issue. I received many solutions for the same radio and most were identical, so I chose the best photos sent to represent those. Some worked for more than one model of radio within a brand and I'll try to make that clear.
The real problem was finding a solution for the Spektrum DX6i radio, which apparently doesn't exist, according to everyone who responded and Spektrum technical support. No one found a way to get that helicopter function to work in the airplane mode. The throttle cut/hold is on a momentary switch, so it would only work as long as you held down the button.
Brett Horton wrote:
"This is the throttle/hold mix I use on my Futaba 10CHG. It can be set up on any available mix. It is the same as I used on the Futaba 9CAP.
"For my electrics, as long as Switch D is in the down position, the throttle is all the way off so no matter what position the throttle stick is in, the motor will not run. I use this on glow- and gas-powered models too.
"It is set up so the engine will remain at idle no matter what position the throttle stick is in as long as Switch D is in the down position. I got this from an article in R/C Report several years ago. I hope this helps fliers to be safe."
I received much mail asking for an Airtronics solution and that came from Ray DiNoble of the Las Vegas Soaring Club. Here's his note:
"Throttle hold using the Airtronics SD-10G transmitter: In the AERO Menu, go to Switch Assign. Toggle down to Throttle Hold and chose any three-way switch. I use switch 10/11/12. As shown, select >11 >OR >12.
"This means the throttle is unarmed at either of these two switch positions, but is armed when the switch is moved up to position 10. I also put a short piece of fuel-line tubing over this switch and color it with a red marker, just in case."
The Futaba t7c solution comes from "nioa" and is nicely laid out on his blog at: http://tinyurl.com/kh82hxo.
The Spektrum DX6i has a momentary kill switch for helis, but the best way I've seen to do one for electrics is to replace the switch with a regular two-position switch. Remember that this will void your warranty.
Check out the photos and captions, then experiment to see if adapting them will work with your particular model radio. Always experiment with the propeller removed from the motor!
Cautions and Warnings
There is only one way to ensure a motor will not start. That's by removing all sources of power to the ESC/motor. Everything else is an additional safety measure, but removing power is the only sure way. The Futaba 12FGH offers the throttle-cut/hold feature for all model types. This is also a feature on Futaba’s 14SG and 8FG, and some other radios.
That protection feature is not advised! No manufacturer recommends or endorses this practice. That is an additional safety measure in the ESC programming, but not for intentional use.
Finally, if you've programmed a switch for throttle cut/hold and you have an unexpected motor failure in flight, make sure that you haven't accidentally activated your switch.
Several of you confessed to finding that this had happened after the fact. It's a good tip to remember.
Departure
Anything we can do to increase the safety of our hobby is good. Thanks to everyone who contributed solutions to this question. If previously unknown solutions come in, I'll relay them.
Next time I'll offer some additional foolproof methods for keeping your system safe.
Transcribed from original scans by AI. Minor OCR errors may remain.
