APM:Plane 3.5.0 released


The ArduPilot development team is proud to announce the release of the 3.5.0 version of APM:Plane. There have only been a few small changes since the 3.5.0beta1 release 3 weeks ago.

The key changes since 3.5.0beta1 are:

  • addition of better camera trigger logging
  • fixes to override handling (for users of the OVERRIDE_CHAN) parameter
  • fixed a pulse glitch on startup on PX4

See the full notes below for details on the camera trigger changes.

For completeness, here are the full release notes. Note that this is mostly the same as the 3.5.0beta1 release notes, with a few small changes noted above.

The biggest changes in this release are:

  • switch to new EKF2 kalman filter for attitude and position estimation
  • added support for parachutes
  • added support for QuadPlanes
  • support for 4 new flight boards, the QualComm Flight, the BHAT, the PXFmini and the Pixracer
  • support for arming on moving platforms
  • support for better camera trigger logging

New Kalman Filter

The 3.4 release series was the first where APM:Plane used a Kalman Filter by default for attitude and position estimation. It works very well, but Paul Riseborough has been working hard recently on a new EKF variant which fixes many issues seen with the old estimator. The key improvements are:

  • support for separate filters on each IMU for multi-IMU boards (such as the Pixhawk), giving a high degree of redundancy
  • much better handling of gyro drift estimation, especially on startup
  • much faster recovery from attitude estimation errors

After extensive testing of the new EKF code we decided to make it the default for this release. You can still use the old EKF if you want to by setting AHRS_EKF_TYPE to 1, although it is recommended that the new EKF be used for all aircraft.

Parachute Support

This is the first release with support for parachute landings on plane. The configuration and use of a parachute is the same as the existing copter parachute support. See

Note that parachute support is considered experimental in planes.

QuadPlane Support

This release includes support for hybrid plane/multi-rotors called QuadPlanes. More details are available in this blog post:

Support for 4 new Flight Boards

The porting of ArduPilot to more flight boards continues, with support for 4 new flight boards in this release. They are:

More information about the list of supported boards is available here:

I think the Pixracer is a particularly interesting board as it is so small, and will allow for some very small planes to fitted with an ArduPilot based Autopilot. It is really aimed at racing quads, but works well on small planes as well as long as you don't need more than 6 servos. Many thanks to AUAV for providing development Pixracer boards for testing.

Startup on a moving platform

One of the benefits of the new EKF2 estimator is that it allows for rapid estimation of gyro offset without doing a gyro calibration on startup. This makes it possible to startup and arm on a moving platform by setting the INS_GYR_CAL parameter to zero (to disable gyro calibration on boot). This should be a big help when flying off boats.

Improved Camera Trigger Logging

This release adds new CAM_FEEDBACK_PIN and CAM_FEEDBACK_POL parameters. These add support for separate CAM and TRIG log messages, where TRIG is logged when the camera is triggered and the CAM message is logged when an external pin indicates the camera has actually fired. This pin is typically based on the flash hotshoe of a camera and provides a way to log the exact time of camera triggering more accurately. Many thanks to Dario Andres and Jaime Machuca for their work on this feature.

Lots more!

That is just a taste of all of the improvements in this release. In total the release includes over 1500 patches. Some of the other more significant changes include:

  • RPM logging
  • new waf build system
  • new async accel calibrator
  • SITL support for quadplanes
  • improved land approach logic
  • better rangefinder power control
  • ADSB adapter support
  • dataflash over mavlink support
  • settable main loop rate
  • hideable parameters
  • improved crash detection logic
  • added optional smooth speed weighting for landing
  • improved logging for dual-GPS setups
  • improvements to multiple RTK GPS drivers
  • numerous HAL_Linux improvements
  • improved logging of CAM messages
  • added support for IMU heaters in HAL_Linux
  • support for RCInput over UDP in HAL_Linux
  • improved EKF startup checks for GPS accuracy
  • added raw IMU logging for all platforms
  • added BRD_CAN_ENABLE parameter
  • support FlightGear visualisation in SITL
  • configurable RGB LED brightness
  • improvements to the OVERRIDE_CHAN handling, fixing a race condition
  • added OVERRIDE_SAFETY parameter

Many thanks to everyone who contributed to this release! The development team is growing at a fast pace, with 57 people contributing changes over this release cycle.

I'd like to make special mention of Tom Pittenger and Michael du Breuil who have been doing extensive testing of the plane development code, and also contributing a great deal of their own improvements. Thanks!

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  • Developer
    More details please?
  • Hi..

    Did I missed something? VTOL support in full parameters list from ArduPlane 3.5.2 corrupt? I am using Pixhawk.




  • hi all!

    I created the adapter


    connected AUX 6 

    my parametr:


    what to do with these parameters?

    RELAY_PIN2,55 -?


  • Developer


    I've replied there, but worth mentioning it here too. The most likely reason is that RELAY_PIN is set to 54, which is the default. That prevents the RPM input from working as it is the same pin, and the rely takes precedence.

    Try setting RELAY_PIN to -1, then reboot.

    Also, a good way to test the RPM input is to direct connect a normal RC channel (eg. aileron) to the aux5 RPM input pin. You should read 3000 RPM (which is 50Hz, the RC out period on plane).

    Cheers, Tridge

  • @Michael Manion @Andrew Tridgell: RPM pulses do not work for me either.

    I opened a discussion about it, here:

  • @GocGoc

    My U7's arrived two weeks ago. Halfway through the build.

  • @Justin L

    It just gets better and better, can't wait to finish mine !! Just waiting for some U7 motors to arrive .

  • @GocGoc.

    If it was VTOL the quad motors could have kicked in at Q_ASSIST_SPEED=13 and prevented the stall. No need to switch to QHover. :)

  • Hi Tridge, thanks for taking a look.  This aircraft is petrol driven so I am sure that was not the problem.  I quite often at all this aircraft and it is incredibly docile.  This event the aircraft just rolled over uncommanded and continued into the ground.  

    I wish it was a VTOL, could of recovered by going into QHover !!! :)

    Thanks again.

  • Developer


    At first glance it looks like a normal stall. The airspeed dropped to 12m/s just before it lost control, whereas it had been flying between 15m/s and 20m/s for the rest of the flight. In FBWA mode the stall prevention only prevents excessive bank at low speed, it doesn't help at all if the plane just slows down.

    It it a pity the current/voltage logging isn't working (is it just not hooked up?) as that would tell us some more about why the aircraft lost speed. The throttle stayed fairly constant. Is there any chance the battery had gotten a bit low?

    Cheers, Tridge

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