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WARNING: Be careful when using a Taranis (or any OpenTx system) to set up an i/c helicopter. There is a trap for the unwary that can lead to a (very!) hot start!
I recently built a NOS Schluter HeliBoy, and equipped it with FrSky gear that I've been using for some time. I had selected the throttle trim to "idle-only" and programmed a "kill-switch" for the engine. I was using a five-point curve for the throttle, and during test flights, I needed to increase the three mid-points to get enough head speed in the hover.
When I re-started after carrying out these adjustments - which were only slight, around 5% - I was treated to the delights of a VERY hot start, and there ensued several seconds (but it seemed longer!) of panic whilst I tried to shut it down!
Moving the mid points on the throttle curve had significantly increased the idle speed.
There is a solution, and that is to apply the curves at the input stage, rather than in the mixers. For a full description of the whole saga, plus the solution, see here:
Throttle trim - potentially dangerous! - openrcforums
I don't think this is an issue with OpenTx per se, but to those coming from other brands it was unexpected behaviour! It certainly caught me out!
It is unlikely to happen with an electric powered heli, as the ESC will usually refuse to arm unless the throttle is fully closed. Having said that, I usually power up my electric models with the "kill" switch engaged on the Tx, to prevent accidentally opening the throttle before I'm ready! Releasing the "kill" switch could also produce a sudden and unexpected spooling up!
I was caught out primarily because it is considered good practice to apply rates and expo at the mixer stage, to ensure all the arithmetic is carried out at maximum resolution. Since a curve is a variation on a rate, I assumed that the mixer would be the best place to apply a curve too.
In this case, I was very wrong, and gave myself quite a fright!
Golden Rule: Apply throttle and pitch curves at the INPUT and rates and expo at the mixers!
I recently built a NOS Schluter HeliBoy, and equipped it with FrSky gear that I've been using for some time. I had selected the throttle trim to "idle-only" and programmed a "kill-switch" for the engine. I was using a five-point curve for the throttle, and during test flights, I needed to increase the three mid-points to get enough head speed in the hover.
When I re-started after carrying out these adjustments - which were only slight, around 5% - I was treated to the delights of a VERY hot start, and there ensued several seconds (but it seemed longer!) of panic whilst I tried to shut it down!
Moving the mid points on the throttle curve had significantly increased the idle speed.
There is a solution, and that is to apply the curves at the input stage, rather than in the mixers. For a full description of the whole saga, plus the solution, see here:
Throttle trim - potentially dangerous! - openrcforums
I don't think this is an issue with OpenTx per se, but to those coming from other brands it was unexpected behaviour! It certainly caught me out!
It is unlikely to happen with an electric powered heli, as the ESC will usually refuse to arm unless the throttle is fully closed. Having said that, I usually power up my electric models with the "kill" switch engaged on the Tx, to prevent accidentally opening the throttle before I'm ready! Releasing the "kill" switch could also produce a sudden and unexpected spooling up!
I was caught out primarily because it is considered good practice to apply rates and expo at the mixer stage, to ensure all the arithmetic is carried out at maximum resolution. Since a curve is a variation on a rate, I assumed that the mixer would be the best place to apply a curve too.
In this case, I was very wrong, and gave myself quite a fright!
Golden Rule: Apply throttle and pitch curves at the INPUT and rates and expo at the mixers!
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