Feature Request APM Plane

Not sure where to post this. Please inform if you know.

These are for APM Plane

Minimum ground speed
The autopilot supports airspeed which usually works beautifully. However, in high winds GPS ground speed can be below airspeed. So far below that the plane will fly backwards when heading to a waypoint. This happens to me in winds near 20 mph. The plane is used for mapping so I set the airspeed as slow as the plane will safely fly. The plane can easily handle the winds otherwise. Maybe include GPS speed with airspeed?
Possible solution: If GPS speed is below desired airspeed then increase throttle until GPS speed reaches desired airspeed.

TAKEOFF bug
Problem: After the plane reaches Take off altitude it drops 50 or more meters on the way to the first waypoint. The default takeoff altitude is 30 meters. If you use that setting your plane will most likely hit the ground before it starts climbing to the first waypoint. Altitude between sequential waypoints seems to be fine.
Solution: maintain altitude from takeoff altitude completion to first waypoint.

I’m glad to test or clarify.

-Brian

You can post feature requests to the Issue Tracker:
github.com/diydrones/ardupilot/issues

MIN_GNDSPD_CM - plane.ardupilot.com/wiki/ardupla … _gndspd_cm

Might solve you’re first issue

Thanks Mark. That is exactly what I was looking for. Mine was set to 0. Plane behaving as expected. Ready for a windy day to fly!

-Brian

Brian,
Tell us more about this takeoff bug you are reporting. I have heard of it or experienced it before. Do you have a log?

Hi iskess,

Log attached. Here’s a video that shows a typical take off. youtube.com/watch?v=CVVOJZ1kNoQ
Fast forward to 3 minutes for the actual flight. You’ll see the plane drop after it reaches TAKEOFF altitude. Also, note in the video the plane stays at MAX THROTTLE after reaching TAKEOFF altitude while heading to waypoint 1 (It passes waypoint 1 during take off and has to come back around - which it does perfectly). It needs MAX THROTTLE while ascending to TAKEOFF Altitude, but once there it could travel at cruise speed to waypoint 1.

Thanks!

Brian

Can you give it a try with less a extreme flight plan? You are using a 40 degree take off pitch angle and an 84% gradient. Try a pitch angle below 30 and move that 1st waypoint further away to get a more reasonable gradient.
I don’t know why, but perhaps the autopilot is struggling with transitioning from such an extreme climb to level flight. It could be related to the aerodynamic behavior of the airframe. Do you have an airspeed sensor? If not, that is likely to solve your problem. I have had odd throttle behavior on my planes that have no air speed.

Tridge acknowledged that this is a real issue that needs to be addressed using some smoothing between takeoff and normal auto flight phases.