Hi everyone,
I’m seeing a behavior in ArduPlane where, during a turn, the aircraft’s airspeed keeps decreasing even though the throttle is already increasing and eventually remains high.
Why does this happen?
Is this expected behavior in ArduPlane during turns, or is there something specific in the control system that could cause the aircraft to continue losing airspeed even with increased throttle?
I’d like to understand the reason for this behavior.
That isn’t expected behavior by the autopilot, but it sounds much more like an aerodynamic effect/lack of thrust than anything that software can solve. Constant airspeed level turns require increased thrust (over wings level flight), and that thrust requirement increases as bank increases. It sounds like your turns are too tight or your aircraft is underpowered (or both).
Thanks for the pointer. I went back through my logs and pulled some concrete numbers to narrow it down:
Across a 2+ hour flight, I found several turns with clear airspeed sag correlated to bank angle. The most telling one: at t≈8281–8293s, throttle climbed to 86% during the turn while airspeed still dropped from 16.5 m/s to 12.8 m/s (a 3.6 m/s sag). A few other turns show similar sag (3.4–4.9 m/s) with throttle peaking in the 45–65% range.
RLL2THR: 10.0TECS_TIME_CONST: 5.0THR_MAX: 100.0 (no ceiling configured)Given the 86% case, is this what you’d expect from “underpowered for the turn” — i.e., is there a rule of thumb for how much throttle headroom above cruise-trim I should budget for turns at a given bank angle? Or does 86% still leave enough margin that this points somewhere else? Happy to attach the full log if that’s more useful than numbers.
It would be better to share a .bin log file.