Update – while everything below still stands the cause of the problem was worse than I thought. In introducing a curve for the aileron differential I had reversed the servos to make it work BUT I had not tested “basic or panic” mode afterwards – and so the aileron controls were reversed in that flight mode – which is kind of ironic. This has made me even more convinced that a basic / panic mode with no mixes is not necessarily a good idea or needs to be done and (re)tested with as much care as the other modes.
I read an excellent article in the BMFA journal ( issue 121 , unfortunately not on-line ) about Aileron Differential / Adverse Yaw but unfortunately never got around to doing much about it until this week. Essentially this is where symmetrical deflection of the ailerons causes too much drag on the lower aileron – just like dropping a flap on one side of the model only.
Last week when I set up my new Hobbyking Phoenix 2000 ( review coming soon ) with quite large aileron throws so that I could use crow braking / spoilers. When I looked at the amount of downward deflection of the ailerons it was very significant and alarm bells rang in my head. I used curves on the Taranis to reduce the downward deflection to 40% and this seemed to work really well.
In my Taranis setups I usually have a basic mode with no mixes as a fallback in case I have programmed something wrong. I have always been quite proud of this feature – until today.
As I circled around for landing I accidently knocked the switch into this basic mode. I wasn’t too worried as it was a simple landing and I didn’t need engine or braking. Unfortunately during the slow turn the model stalled, dropped a wing and dived into the long grass.
What had happened was that the 40% limit on the downward aileron deflection had been removed and the excessive downward deflection on the inside wing during the turn had created so much drag that the wing had stalled.
Thinking back to my first slope session a couple of weeks ago when a crashed another plane the symptoms were very very similar.
So the lessons learned :
1) aileron differential is very important
2) you can be too clever when programming transmitters sometimes
I will update the 6 channel Taranis eepe this week