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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SO far Im loving the new L1 nav controller. I am wondering however, what value I should adjust to get the plane to tighten up its turn at the waypoint and get back on track to the next, since xtrack seems to be greyed out now.


The plane tracks very well once its on the line between waypoints, but swings wide after it makes the turn off the waypoint and eases back onto the line. I would like it to get back on quicker.


Hi Matt,

The plane tracks very well once its on the line between waypoints, but swings wide after it makes the turn off the waypoint and eases back onto the line. I would like it to get back on quicker.

There are two things you can do:

  • reduce NAVL1_PERIOD a bit. Try reducing by 5 at a time until you are happier with it.
  • use a larger WP_RADIUS value

Cheers, Tridge

The L1 controller is one of the best things to happen to Ardupilot. I love it. My plane stays on the flight path, and guided is a perfect circle. Way to go!

@Stephen: What values did you end up with ?

Period of 30, haven't touched damping yet. I have a 10 pound airplane with a seven-foot wingspan. 

So you had to step up from 25 ...? What aircraft do you have ?

I was doing the last check in my house before test the 2.73 release and  I have noticed in MP that there was problem with the level.


I connect the APM with MP and the level moves until it keep in the following position although the plane was in the correct position.

(roll level moves to right along until this position)

(See the image attached)

I re loaded  the 2.65 release and everything come back to normal situation.

I installed  2.73 release again and got the same issue.


Do you have any comment or suggestion…

The APM 2.5 with the 2.73 version of code, work "out of the Box" or "Plug and play". Thank you Andrew .

@Leopoldo , i have the same matter of issue , but with APM 1.4 In my case the HUD drift right . I don't know what happen.  I change the orientation of board (APM 1.4) to 90 degrees roll, and looks nice.in test bend not in airplane yet .

Nikos, I found the solution to this issue. 

You should open MP in the configuration Tab you have an option to level the APM when you install in the plane.

Press the level key and wait when you get a "complete" the HUD will be in the correct position.

Flew my X8 with the 2.73 firmware yesterday.

This navigation control is excellent.

The aircraft now loiters in a perfect circle with the default settings whereas with the prior version it loitered in a square.

It hits every way point exactly and the throttle management in auto seems much improved for some reason.

All in all a fantastic upgrade experience.

Did not try the new elevon output option though.

Did someone nearly hit you with a TBS Caipirinha by any chance?

Yes they did!


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