The ArduPilot development team is proud to announce the release of version 3.5.1 of APM:Plane. This is a minor release with primarily small changes.

The changes in this release are:

  • update uavcan to new protocol
  • always exit loiter in AUTO towards next waypoint
  • support more multicopter types in quadplane
  • added support for reverse thrust landings
  • added LAND_THR_SLEW parameter
  • added LAND_THEN_NEUTRL parameter
  • fixed reporting of armed state with safety switch
  • added optional arming check for minimum voltage
  • support motor test for quadplanes
  • added QLAND flight mode (quadplane land mode)
  • added TECS_LAND_SRC (land sink rate change)
  • use throttle slew in quadplane transition
  • added PID tuning for quadplane
  • improved text message queueing to ground stations
  • added LAND_THR_SLEW parameter
  • re-organisation of HAL_Linux bus API
  • improved NMEA parsing in GPS driver
  • changed TECS_LAND_SPDWGT default to -1
  • improved autoconfig of uBlox GPS driver
  • support a wider range of Lightware serial Lidars
  • improved non-GPS performance of EKF2
  • allow for indoor flight of quadplanes
  • improved compass fusion in EKF2
  • improved support for Pixracer board
  • improved NavIO2 support
  • added BATT_WATT_MAX parameter

The reverse thrust landing is particularly exciting as that adds a whole new range of possibilities for landing in restricted areas. Many thanks to Tom for the great work on getting this done.

The uavcan change to the new protocol has been a long time coming, and I'd like to thank Holger for both his great work on this and his patience given how long it has taken to be in a release. This adds support for automatic canbus node assignment which makes setup much easier, and also supports the latest versions of the Zubax canbus GPS.

My apologies if your favourite feature didn't make it into this release! There are a lot more changes pending but we needed to call a halt for the release eventually. This release has had a lot of flight testing and I'm confident it will be a great release.

Happy flying!

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Comment by Jason Franciosa on March 22, 2016 at 6:27pm

I tried that as well, The strange part is I have no issues with 3.5.0, only 3.5.1. This is an original 3D Robotics pixhawk as well, not a chinese version

Comment by Andrew Tridgell on March 23, 2016 at 12:22am

@Jason, I'd like to try to reproduce the problem. I strongly suspect it is related to something in your parameters.

Can you please do this:

1) downgrade to 3.5.0

2) connect with MissionPlanner and save a full copy of your parameters

3) send me the parameter file

After you have captured the parameters, try setting the FORMAT_VERSION to 0. Then reboot. This will reset all your parameters to defaults.

Then try loading 3.5.1 and reload all of your parameters. Please let me know if this fixes the problem. If it does then I will try to reproduce by loading your parameter file.

Cheers, Tridge

Comment by Tamás L. Páll (Tom) on March 23, 2016 at 2:27am

Guys, is it possible that once a new FW is available the plane "doesn't want" to fly with the old version? 

Comment by liuyi on March 23, 2016 at 7:12am

I would like to ask, how to use the parachute function, my pixhawk firmware has been upgraded to 3.5.0. I also set the parameters in accordance with the, but the test process is not prompted  Mission Planner  "Parachute:Not Flying". Ask the parameter of the Mission and Planner ground station set up detailed

Comment by Jason Franciosa on March 23, 2016 at 7:17am

@Tridge. I tried that and it worked at first, but, after I loaded my param file back to 3.5.1 now it boots up, runs the configuration. then it just goes dead. There is no light on the main LED anymore and the lights on the top sides are just solid. Something with my param file is not happy with 3.5.1.

I sent you my param file in a PM.

Thank you,


Comment by Jason Franciosa on March 23, 2016 at 7:40am

Ok, I reset the paramfile again and there is no issue's. As soon as I load my param file and reboot, it causes the pixhawk to lock up.

Comment by Guy Tzoler on March 23, 2016 at 7:53am


I saw that the QuadPlane page at says "The code defaults to a Quad-X frame" is can it also support + configuration?

i am wondering about putting 2 motors on the wings 1 on the nose and one pusher that will tilt...

what do you think?

Comment by JB on March 23, 2016 at 8:47am

Guy Interesting config. Might have to try it if it's supported. (Which I think it is btw)

But maybe a tricopter with pivoting and swiveling tailrotor would be simpler again and fix the yaw problem in wind at the same time?

Comment by Andrew Tridgell on March 23, 2016 at 2:20pm

@Jason, I have reproduced the problem with your param file, and I will work on a fix today. Thanks for reporting it!

Comment by Jason Franciosa on March 23, 2016 at 3:15pm


thank you!


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