The APM dev team is delighted to announce the release of APM:Plane 2.74, a major new release with a lot of new features. This release is recommended for anyone flying fixed wing aircraft with an APM2 or PX4.

There are a lot of changes in this release, but some of the highlights are:

  • new APM_Control attitude controllers.
  • new TECS speed/height controller from Paul Riseborough.
  • two new flight modes, ACRO and CRUISE
  • new camera trigger by distance system, for better aerial mapping
  • dozens of small fixes and improvements from two months of development
  • lots more documentation, including tuning guides for all the new parameters

Scroll down for a more complete list of changes, but before that I'd like to give you a bit more detail on the highlights above.

New Attitude Controllers

The new "APM_Control" attitude controllers have been in development for a long time. Originally developed by Jon Challinger last year, they were extended by Paul Riseborough and made compatible with the existing parameter names. The key advantage of these new controllers is their improved handling of noise, and much better ability to tune for your aircraft. There is a new tuning guide in the wiki which gives detailed instructions on how to make the most of the new capabilities.

One of the big effects you will see with the new attitude controllers is better handling of pitch compensation in turns. The new PTCH2SRV_RLL parameter makes tuning for flat turns much easier, which has been a major source of frustration in the past.

The new controllers also handle sensor noise much better, especially if you use any D term in your roll or pitch controllers.

New Speed/Height Controller

The new TECS speed/height controller is the second major controller change in this release, and will make a world of difference for aircraft with an airspeed sensor. After a lot of testing I decided to make TECS the default in this release, although you can switch back to the old controllers using the ALT_CTRL_ALG parameter if need be. If for some reason you find you do need these old controllers then please let me know, as I am planning on removing the old controllers in the next release.

The previous airspeed controller for speed/height suffered from a major problem that it gave absolute priority to airspeed. If the aircraft could not achieve the target airspeed you had set then it would dive to gain speed, even to the point of diving into the ground. This made it quite fragile, and you had to be very sure of your airspeed configuration.

The new controller operates over a range of airspeed values, set using the ARSPD_FBW_MIN and ARSPD_FBW_MAX parameters. That controller will try to meet both the airspeed and altitude demands of the mission, but if it can't reach the target speed it will happily fly a bit slower, as long as it doesn't get below ARSPD_FBW_MIN. You can control the relative priorities of speed versus height using the TECS_SPDWEIGHT parameter. See the full tuning guide for details.

New ACRO flight mode

After a suggestion from Thomas in the 2.73 release thread, we have added a new ACRO flight mode.

This modes brings rate controlled stabilization to APM:Plane, and should help give you an "on rails" manual flight experience. It is a lot of fun to fly, but it is not for beginners!

We're planning on expanding the ACRO mode in future releases. Right now it is great for "locked in" flying, and also good for loops and handles inverted flight very nicely. It doesn't yet handle knife-edge or prop-hanging.

New CRUISE flight mode

After a suggestion from Hein, we now have a new CRUISE flight mode. This mode is ideal for longer distance flying without a pre-programmed mission. It is like FBWB, but also does ground track heading hold, with heading update via aileron or rudder.

I've been testing CRUISE at my local flying field, and it is the easiest mode to fly in APM. Just steer the plane around the sky, and when you stop steering it locks onto a ground track and holds it. It isn't a good mode for takeoff and landing, but once you are in the air it is great.

New camera trigger system

When using APM for aerial mapping where you want photos taken at regular distances, the previous system was to setup a grid mission with a "camera trigger" mission item at regular intervals within the mission. That worked, but led to overly large and complex missions. You can now just set a single parameter CAM_TRIGG_DIST to the number of meters of flight between photos, and the APM will take care of when to trigger the camera. This makes for much simpler missions, and also works in other flight modes, including FBWB and CRUISE.

Lots of smaller changes

As is usual with a new release after a couple of months of development there were a lot of smaller improvements based on feedback from users. Many thanks to everyone who gave feedback and contributed patches!

Here is a partial list of the changes:

  • added new GND_ALT_OFFSET parameter for ground station barometric correction
  • made it possible to set the failsafe battery voltage and battery level at runtime via parameters
  • added MIXING_GAIN parameter for controlling the elevon and v-tail mixers
  • fixed stick mixing range in AUTO modes  (thanks Soren!)
  • fixed mode logging in dataflash
  • added support for the EagleTree I2C airspeed sensor on PX4
  • added new RCMAP_* parameters for re-mapping control channels (good for DSM and SBUS receivers on PX4)
  • made it possible to configure board orientation at runtime, to make setup easier without rebooting
  • switched to new task scheduler for more accurate internal timing
  • added a new RELAY_PIN parameter for setting up camera trigger via a digital pin
  • added secondary rudder support, useful for when a separate servo is used for a nosewheel and the rudder, or for v-tail planes with nosewheels
  • fixed RTL glide slope when starting above the target RTL altitude. Descent should now be smooth over long distances. Many thanks to Kitsen13 for raising this.
  • fixed a bug with FBWB airspeed control. Many thanks to Gabor for reporting this
  • Added FS_LONG_TIMEOUT and FS_SHORT_TIMEOUT parameters. Many thanks for the suggestion by Aleck
  • fixed handling of deadzone parameters on RC channels. Many thanks to Soren for reporting this
  • many small C++ fixes from NeuroCopter. This sort of detailed review of our code is much appreciated!
  • fixed analog in handling with some unusual devices - thanks to Andi for noticing this!
  • added support for apparent versus true airspeed calculations based on pressure altitude, for better flight control at higher altitudes
  • avoid writing unchanged bytes to EEPROM, for faster updates and less wear on the chip
  • cope better with large yaw changes in the AHRS code
  • improved the reliability of USB connections on PX4
  • added PX4 support for RELAY (thanks to Marco Bauer)
  • fixed handling of high spin rates in AHRS (thanks Jurgen!)
  • removed support for the old APM1 1280 based boards.

This new release has a lot of new features that should improve the flying experience for all APM users. The APM dev teams wishes all APM users many enjoyable flights, and we hope you have as much fun flying this release as we had making it.

Happy flying!

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@Andrew, thanks. That is great.

Hi there, I have installed this in to an X5 airplane... here are my issues if you can help please.

1) I have the plane flying in manual mode well nice and level

2) in FBWA mode I can tune my aileron response so that nav roll and roll are very good and responsive in the graph

3) in FBWA mode I can NOT seem to get my pitch to keep up with the nav pitch. This I believe is causing some very large radius turns. I have NAV p term set all the way to the max at 1.0

4) I have redone the calibration on the radio with limited endpoints on the roll in order to gain some pitch authority. This did work but not enough.

5) I have increased the mix on the elevon mixing (in advance paramters) but anything past .7 means the plane is very difficult to control in stabilized mode.

What I see here is the need for separate elevation and aileron "mix gains" not nav gains but mix gains.

I have also noticed that when in stabilized mode I get pitch more authority compared to when in FBWA mode.


I have attached a log file of one flight... any help appreciated!|




Hmmm...I guess I should switch to XPlane then!  Anyone else using 2.7x with FlightGear for HIL?

Hi Charles,

I'd guess that the update rate from FG may be too slow, or the gyro scaling is off.

I'll try it later this week and let you know.

Cheers, Tridge

Has anyone got a working set of parameters for the SIG Rascal in the Flightgear HIL simulation?

With v2.68 HIL I was able to get a stable plane that replicated the real life behaviour of a plane but in v2.74 HIL the plane is all over the place and I'm battling to get any sort of stable flight.

Hi Andrew

Thanks for the info. Looks like a little complicated but I think I can make it work. Thanks again 

Thanks for the response, however the pitch is lagging quite a bit compared to other platforms that were flying on different firmware...

When in FBWA mode I can get good aileron response but elevator gives me almost no movement... the climb rate is very low. So this means I will not have good elevator authority in Auto mode.

The other issue which may or may not be related is that the throttle and altitude are constantly going up and down. It seems the plane is pitching down to gain speed and the throttle is off... then it throttles up as it climbes back to targert altitude. It does this cycle continuoulsy and can be seen in the log easily in the RTL circle.

I revereted to an old firmware and most if not all of that cycling went away, however I still did not have enough elevator authority.

Finally and probably the most interesting thing is on the ground in FBWA mode I can get the same elevator deflections as I do in stabilize mode (in stabilize mode flying I have more than enough elevator authority) HOWEVER HERE IS THE KICKER! as soon as the plane is flying I lose all elevator authority and can't "pull up" I assume there is a gain scheduling going on where the faster I go the less control authority is available to the outputs. This make sense but it is being reduced too much and only on elevator... my aileron authority seems fine.

Could this be related to the "new method of elevon mixing" where all mixing is done onboard and none in the TX?

Thanks guys.


BTW I am not using an airspeed sensor and have it unchecked. The throttle management is very cyclic compared to other revisions.


Hi Tridge, thank you a lot... next week end I will load new release and  test it.

Regards, Leopoldo

I had the same problem on my X8. I had to turn my pitch limits way up, and go back to the old method of Elevon mixing. That helped, but my authority was still far less than what auto uses. The problem was only in FBW, auto worked fine. Search my posts, Tridge gave some good advice to try but since I was pressed for time before a big project I just abandoned FBW and haven't looked back yet.
Now I'm focused on a new build of a conventional 4 ch. aircraft.

I have the same issue on a xeno flying wing and posted here

I was able to partially gain elevator authority by increasing the mixing gain but it is a workaround as I still don't have enough elevator authority in FBWA and had to reduce aileron end points to compensate . My xeno is a slow flyer, so it performs quite well in auto mode despite the elevator authority still being a bit low

Interestingly my sky walker does not have this issue which makes me wonder if the new elevon mixer needs a bit of balancing ??

Also is there another parameter that we are not seeing that could give more elevator authority (pitch p is maxed at 1.0 and mix gain is 0.8, and have increased max pitch angles)



Can I ask - If I am using arduplane without an airspeed sensor (I have some on order) should I use the default TECS speed/height controller on or disable it until the airspeed sensor is installed and calibrated?



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