[TheOtherCliff]

During testing, make sure that you hover at throttle position that does not climb or descend, with manual throttle, for several seconds, before switching into AH for the first time on any flight.

[octavvian]

Tested, confirm the lost of alt fix, but know when switch from stab to ah it jumps 20 cm and tend climb , can't test the right way, here it's storming (wind) so even indoors pressure isn't stable. I'll repeat on better weather. Thanks.

[TheOtherCliff]

Tested, confirm the loss of alt fix, but know when switch from stab to ah it jumps 20 cm

Does it jump up or down?  Always up or always down or sometimes up sometimes down?

tend climb

If the climb is very slow, then thermal calibration (Attitude page) may be needed.  The board warms up for the first 5+ minutes after plugging battery in and as board warms up, the quad climbs.  Thermal calibration fixes this.

A video showing your problems would probably help, and be entertaining too. 

[octavvian]

Yes, will be, at least entertaining ...
I'll try a video next time.

[jdl]

I'd like to report that tests with a myself compiled "dirty" Revo firmware (based on Next.589) incorporating the change in post #4 were successful for me.

This change from TheOtherCliff in post #4: ...flight/libraries/math/pid.c fixes for me the ugly transition from Rate to RTB  I've observed when the copter is in more challenging attitude / orientation with throttle away from ThrustLimits/Neutral setting.

Transition from Attitude to AltitudeVario is also butter-smooth now, as it was in 16.09.

I guess this fix should be made "official".

[f5soh]

I guess this fix should be made "official".

Here is : https://bitbucket.org/librepilot/librepilot/pull-requests/509

[sam028]

I confirm the transition is now extremely smooth and barely unnoticeable.
Well done!