RTL caused the craft to ascend and then immediately descend to RTL alt

I ran into an issue where hitting the RTH switch caused the aircraft to rise 30m (as instructed by the RTL_CLIMB_MIN parameter), and then immediately descend to around 110m (with an RTL altitude set to 100m).

The odd thing is that plotting the log, I always see TAlt at the same value:

I have a video of that bit but the forum doesn’t support uploads.

Here’s the blackbox log:

The docs say that RTL should descend to the target altitude linearly, not immediately, yet that’s not the behavior I see.

This is very interesting. The plane did descend to the correct 100m altitude. But I agree that based on the description for RTL it should have been a much more linear or gradual descent. I haven’t used RTL_CLIMB_MIN but I’ll be watching to see the outcome of this discussion. Have you tried to trigger RTL when you were below 70m? I’m just curious what it would do in those conditions.

Do you have terrain follow enabled?

Sorry, for some reason I didn’t get notified for these replies. This was a bug that was fixed, RTL now keeps the additional altitude and continues returning. @Allister, if I was below 70m it would continue returning at 100m, it was only “extra” altitude above the return altitude that it discarded.

What did you fix or change?

This is the issue with the fix:

I also have a PR open that makes the craft climb to the RTL altitude before turning, which should greatly improve this feature. Let’s hope it gets accepted.

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