Most of my wing build (Z89, SonicModel HD Wing, AR Wing Pro) are using folding propeller.
Take-off is kind of “very” risky with that kind of frame using arduplane Auto Takeoff because if motor is not spinning before launching the plane (Idle Throttle is equal to 0% by default), there is a high risk that the ESC has to retry its “startup procedure” due to the torque required at startup-time ( if propeler is folded or unbalanced) . causing the propeler to have a 1-2 sec delay before really spinning… leading to some crashes… because wings have fewer attitude authority than t-tail plane
What’s-more if the propeller itself is heavy or just big, the torque required to speed-up the motor will generate some roll at launch-time, what is very unwanted at takeoff, causing loss of lift… leading to some crashes…
INAV has a parameter for that issue : nav_fw_launch_idle_thr
Here is the associated documentation for folding propeler :
It can be very stressful for your motor, props and even fuselage if a folding propeller is spinning instantly to 100% power if it is folded. So, you can use a low value like 1100 to make sure the prop is open and in balance before launch.
My proposal is to implement a param TKOFF_IDLE_MODE with 3 values possibles:
- MODE=0 throttle when idle is equal to 0%
- MODE=1 throttle when idle is equals to param TKOFF_IDLE_THR (static value, in % of motor PWM) . The motor should start to spin when RC MOTOR INPUT >1500 for safety reason.
- MODE=2 throttle equals RC MOTOR INPUT (eg channel 3), limited by the upper value define by TKOFF_IDLE_THR (in % of motor PWM).
so basicaly, MODE=0 is the current behaviour, MODE=1 is the INAV feature, MODE=2 allow the pilot to take manual control with its RC on the motor startup, with a predefined “security” limit .
To sumup my main feature request is to have a “balanced folding propeller” BEFORE launch time… and the only known way is to have a 10-30% throttle when the plane is IDLE. INAV have this feature for this specific prupose.
Does enyone has some more ideas on that “TakeOff : Idle Throttle” feature ? any other mode in mind ?