APM:Plane 2.74 released

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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  • Hey all!

    I just tried my Twinstar with the latest 1.75b. It barely worked in FBWA , i couldnt almost nudge it. I raised P a bit and it then worked ok. I have more to do there. But, in the new excellent cruise mode i did not have any elevator at all? I even tested it on the ground afterwards and the elevator did not move a bit? Is this a bug or a settings problem? Other than that i was really satisfied except that the throttle bumped up a little much in Cruise and RTL so I need to get that sorted.

    I have a Futaba 7C and have changed the endpoints a little to match Multiplex throws. Not that much at all. Manual mode works good so the plane is stable.

  • Ok I just flew a way point mission and the results were mixed. It kept climbing and descending with the throttle and and off but that was soon fixed when I altered the Nav AS P gain. But when it flew to a waypoint it was pretty poor at staying on the line and was awful at tracking to the next way would overshoot the next way point awfully then struggle to get back on track..

    any ideas? 

  • Does anyone have the parameters file for an X8? Going flying later with the NEX7 for mapping and would like to try a mission :) thanks

  • Hi,

    Is there a way to connect MP to APM trough bluetooth?

    I have a BT modul connected directly to apm. It works nice on my phone. I can also ,ake a bridge out of my phone to MP. I can connect that way. But i would like to leave my phone out when i am at home.

    It would be nice to be able to connect directly, leaving that "UDP thing" out of the... :)

    Also people who use their phone as telemetry groundstation connected to 3dr radio trough BT need this.



  • I am having trouble with my RC RSSI in my new build. I have 2 other APM aircraft with no trouble but with the older firmware. I have tried several A pins and I always get an RSSI of about 180-190 displayed on the HUD (User items: rssi). When I turn of my DragonLink Tx it does not change. I tested the RSSI pin on the DL Rx and it reads 2.75v max, and .89v when the Tx is off. Right now I have RSSI_PIN set to 9, but it doesn't change the reading even if I disconnect it, so it must not be reading anything. I tried a different Rx and it's no different. Did this get broken in the newest firmware?
    Any ideas?
  • 'RLL2SRV_P value is too high' ...So where do I turn it down? I have been looking in the manual tuning guides and on the mission planner but cant find it?? :/ Very confusing. would appreciate any help guys :) thanks

  • Non airspeed sensor airplane – how do I make it fly faster?

    In Loiter and Auto mission it flies between 50 and 54% throttle. I tried changing the cruise airspeed and cruise throttle but it makes no difference? What are the controlling parameters that I need to change?

    I even tried a higher pitch prop but the cruise speed was the same and the throttle % went down so that it wouldn’t go any faster. This really has me confused. I would like to cruise a little faster with a target throttle of 60-65%. How can I make this happen?




  • Where do I change the PiDs for stabilisation mode? IM completely lost, i hav everything set up right for a first flight on a X8 but cant find stabilisation mode tuning. Also is NavPiDs for tuning the autopilot? Many thank guys

  • Does anyone have a Skywalker parameter file with the new TECS controller settings that I can use as a starting point?
    I'm about to maiden a new 2013 Skywalker 1880.
    Thank you.
  • I'm having a bit of difficulty understanding the difference/relationship between the value of Throttle 0-100% Cruise percentage and the Airspeed Cruise m/s on the Arduplane PIDs page of MP.     


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