Drone descending on RTL

ArduCopter Copter 3.2
1

I got Ardupilot set up and working for the first time on an APM 2.6 board. I was testing the RTL function and I set the my RTL altitude to 200 (2 metres), and ran my first test by taking off in stabilize, flying approximately 5 metres away while keeping the drone at 2 metres altitude then activating RTL.

The drone returned to the launch spot, but descended as it did so, nearly touching the ground at about the point it launched. So it looked like it was flying directly for the spot on the ground where it launched, not at 2 metres, then it climbed straight up to 2 metres, and continued the landing procedure as intended, it hovered for 5 seconds at 2 metres then landed.

Can anyone help me with why it is doing this, it did it on repeated attempts.

ardupilot
ardupilot8645×3690 236 KB

2

Some points:
APM flight controllers are very old and not supported - you likely wont find anyone to help in any detail

2m is very low and pressure changes from prop wash could come into play. If you are able to look in a log you may find the copter thought it was maintaining altitude.

RTL_CONE_SLOPE - I dont even know if this existed in those early Arducopter versions!
values from 0.5 to 10.0
1 means 1m out 1m up, 10m out 10m up (very shallow inverted cone)
2 means 1m out 2m up, 10m out, 20m up (shallow inverted cone)
3 means 1m out 3m up, 10m out, 30m up (steep inverted cone)
and so on.
If the copter is within the cone it wont climb

3

V3.2.1 (last version for APM) was long before Cone Slope.

4

So maybe RTL will just start descending instead of climbing to an RTL altitude until the home position is reached

5

Thanks for the response, there is an RTL altitude parameter though, and I believe I saw it set up to do this on an old tutorial.

I will try at a higher altitude, just a bit wary of sending it too high until I know it behaves correctly or safely.

6

Just be prepared to switch into Stabilise mode and take control

7

Think it’s supposed to rise to the RTL altitude. I could blow the dust off a craft with an old APM and try it :grinning:

OK, I’m not going to fly it. But I connected it to MP and this is all you get for RTL with V3.2.1:

Old RTL
Old RTL1536×77 34.4 KB

8

And it was the RTL_alt parameter I had set. So it should have remained 2 metres or climbed to 2 metres. but it flew right down to the ground.