ArduPlane 2.73 released

I've just released ArduPlane 2.73 as a bug fix release for several important bugs in 2.72

The main reasons for this release are:

  • fixed a noise and scaling problem with airspeed sensors
  • fixed a potential flyaway problem with the L1 navigation controller
  • improved handling of poor GPS velocity for attitude correction

This release does not contain the new attitude controllers that I previously said would be in 2.73. Paul and I decided that it would be better to hold those over to the next release, and get this release out with just the above critical bug fixes.

The airspeed problem stemmed from a changed introduced in 2.72 to make ArduPlane automatically scale analog inputs with board voltage. That change was good for voltage and current sensing, but it added a lot of noise to airspeed sensing as the 3DR airspeed sensor is ratiometric (the sensor output scales with the supply voltage). The fix was to add support for ratiometric analog inputs. This release also fixes a bug in the airspeed ratio handling. To confirm the fix I have been driving around in my car with an APM2 and PX4 logging airspeed and GPS speed - that test confirmed the airspeed sensing is now accurate.

The flyaway bug in L1 was caused by an unusual situation where the previous waypoint was equal to the next waypoint, which can happen when a mission is interrupted and restarted. The L1 controller would then level the wings and fly straight ahead until the operator intervened. The bug fix was to make the L1 controller detect this situation and track directly to the next waypoint. I don't think many users would have seen this bug, but it definitely could happen and warranted a bug fix release.

The GPS handling bug was related to the MTK GPS, which can be very slow to report loss of GPS lock, which could lead to very poor attitude from DCM and even a crash if the plane tries to turn while the GPS is reporting incorrect velocity information. The fix was to watch the satellite count, and stop using the GPS velocity for accelerometer correction when it had less than 6 satellites. This is selectable with the new AHRS_GPS_MINSATS option.

Other changes

While this release doesn't have the new attitude controllers I decided to leave in some other smaller changes that have been made since the 2.72 release that I consider to be low risk, including:

  • fix the PX4 barometer driver to run at full rate
  • fixed handling of a saturated compass on PX4
  • added COMPASS_ORIENT option to support external compasses
  • fixed the compass in HIL simulation
  • added GCS messages to flash logs
  • allow 3D accel calibration over MAVLink
  • Added new ELEVON_OUTPUT option
  • removed MANUAL_LEVEL option (manual level is now always on)
  • improved pitch handling when inverted

Of these, perhaps the most useful is the ELEVON_OUTPUT option. That makes it possible to setup your transmitter with normal aileron/elevator and get the APM to do a software elevon mixer on output. That gives better control in FBWA mode than the previous elevon options.

I recommend that all users of 2.72 upgrade to 2.73. Happy flying!

Cheers, Tridge




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  • Has anyone been able to get the new ELEVON_OUTPUT mode to work? I tried this by setting my transmitter to normal aileron/elevator output and when I move the sticks on the controller the surfaces move the correct direction but in autopilot mode the surfaces do not move the correct direction. I can't figure out why it is only half working like this.

  • Hi Andrew.

    Could you tell me what conditions needed to make motor work in auto mode or RTL mode.

    In flight last Saturday use my own GCS, With a fixwing plane, at airspeed 10m/s, height 15-20m to ground, and The distance from plane to GCS is about 40m, I switch mode from stabilize to auto, then,the motor is shut down, and plane crashed.

    Some one tell me if airspeed less than 3m/s, the motor will be shut down. Could you tell me more thing about auto/RTL mode? What conditions does APM/ArduPlane needed to make motor work in auto/RTL mode?

    Yesterday, I  analysis mavlink message between APM/ArduPlane and GCS, and I found I lost Home point data to upload. perhaps this is one reason which make  motor shut down?

    Sorry for my poor english, expect your help.


    This is my own GCS developed by Visual C++, but it's telemetry data format not same with tlogs, I will try to make it compitable with tlogs in next.


  • Hi...I've been trying to fly 2.73 (on an APM 2.5) using Hardware in the Loop with Flightgear.  Everything connects and starts up just fine.  Manual and stabilize also work well.  However, when I switch to auto mode I get a minute or two of stable flight before the reported pitch (in Mission Planner) suddenly starts to drift from actual (Flightgear).  This causes a pitch response on the plane which it really doesn't need.  Depending on which way the drift happens it either pitches up and stalls or nose dives.  At this point the reported attitude is usually spinning wildly and the plane cannot recover.

    Has anyone seen behavior like this before?  Any thoughts are appreciated.  Thanks.

  • I mostly use Arducopter with an APM2.5, and I'll be soon using my old APM2.0 with a Funcub. There are several things very nice with Arducopter I didn't find in Arduplane like UserCode and UserVariables to implement some custom code, and COPTER_LEDS to have visual information, like GPS fix, flight mode, etc.

    Do you plan any release with those elements ?


  • I got mine work today, and all I done is turned off compass (magnetometer). Plane is rock stable, RLT, FBWA and loiter works, APM don't want to kill my plane anymore, I'm happy again :D

    But then another question rises, If my board is yaw180, do I need to set onboard compass also yaw180, or this value is relative to the board?

  • What could case the APM not to change speed when i aply full throttle in FBWB.

    Nothing happens, really.... 

  • @kullman, that means your PPM output is OK form the Rx. did u try using normal PWM in to all channels. do the servoes respond. if it does that means your PPM encoder on the APM2.5 is OK. have you shorted the correct pin nos. 2&3 on the input side of APM2.5.

  • you can define the loiter radius at the bottom of the planner tab of Mission Planner. yo can aslo define waypoint radius. once you upgrade the arduplane yo do not have to run through the configuration. but it is always a good idea to rechk radio calbration and hardware in the configuration tab.

  • I'm upgrading from 2.7.1 to 2.7.3. Is it necessary to do the APM Setup after the upgrade??

    Also how can I define my loiter radius? From the wiki it looks like it's defined as the waypoint radius which determines when a way point is considered reached but when I change that I still seem to get a larger loiter area than what I'm specifying. I'm trying to get a smaller loiter radius so the plane doesn't get away from me while I go in the house to sit at my monitor.

  • i used mission planner to upload the code. you can also use Qupgrader also. i have cut a slit where the USB port is. so  it is easy to connect to USB.

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