Query - hard left turn on take off - first waypoint too close?

ArduPlane Plane 4.3
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Hi, I am using a Pixhawk6C running 4.3.1 and MP1.3.79 in an Avios Grand Tundra fixed wing tractor plane. My Tx is a TX16S running EdgeTx 2.8.0. I have just completed installation and I am flying some first flights to test modes, manual, stabilise, autotune and auto (mission). On my first test of auto/mission mode (flight 4), the plane rotated and then turned sharp left and then flew a wide right hand arc seemingly in order to pass through waypoint 2 in such a way that when it left waypoint 2 its heading was well set up for waypoint 3…if I want a straight climb out from take off do I have to put waypoint 2 further away from runway or can I achieve a straight climb out some other way. The Mission Planner Plan seems to limit how far out I can place waypoint 2 using WP drag and drop on the map…
Also, am I right to interpret the airspeed plot as showing that the plane flies reasonably in airspeed range 8-13m/s? Note that I landed the plane manually but stalled at about 1.5 m altitude just before touch down…Log here
Dropbox - 24 4-12-2022 7-59-40 AM.bin - Simplify your life

and screenshot of waypoints on map in Mission Planner

Thanks, Richard

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The left turn on takeoff was not deliberate. This looks like classic left-yaw on a taildragger tractor aircraft caused by motor torque. The path had nothing to do with the 2nd waypoint.
The trick with tailtraggers like this is to advance the throttle slowly to give time for the rudder controller to compensate for the throttle yaw torque.
I suggest the following parameters:

  • TKOFF_ROTATE_SPD = 8
  • TKOFF_TDRAG_SPD1 = 4
  • TKOFF_THR_MAX = 75
  • TKOFF_THR_SLEW = 25
  • GROUND_STEER_ALT = 2

that will slow down the takeoff, making it much smoother and will give time for the rudder to compensate for the yaw torque

1 Like
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Many thanks Tridge, I’ll try those parameter changes and report back.