When Leonard isn't flying big drones like this:
He's working on improving the performance of ArduPilot. His latest contribution, developed in conjunction with Randy, is pretty big. So big, it will be a while before it can be incorporated into a beta release.
"New Loiter" is a more responsive Loiter mode which accepts lean angle inputs from the pilot, making it feel more like AltHold mode. Despite accepting lean-angle inputs, the position, velocity and acceleration controllers remain active at all times, ensuring the vehicle fights against disturbances. This is quite different from PosHold mode which does not attempt to maintain position or velocity while the pilot provides stick input. New Loiter also includes active braking when the pilot releases the sticks.
A lot of testing has been done, in SITL and real aircraft, but we need more, and hope that some of the more experienced members of our community can assist. If you think this is you, read on. We'd love for you to help out (very carefully, and at your own risk). Prebuilt firmware for Pixhawk, the Cube/PH2.1 and PixRacer is here: https://goo.gl/tyJ1mT. If you decide to try it, please post links to your log files and descriptions of your test vehicle in the comments below.
Some of the outstanding issues that need to be resolved before this can go into master:
QuadPlane and Sub position controller gains have changed (because they are the same as Copter) so we need to either pass in the default gains to the position controller constructor or have the vehicles actively set the defaults as part of their startup.
More testing of Copter to ensure the vehicle doesn't move around too much after the pilot releases the sticks
More testing that the porpoising in auto has been resolved
More testing of Sub and Quadplane to ensure nothing has been broken
A full description is in the Pull Request, https://github.com/ArduPilot/ardupilot/pull/7258