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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Sorry, I may have misunderstood your question. If you look at standard parameters and RC Channel Function, there appears to be a limited list of assigned functions. At least if one chooses to use the standard code. Every time I have tried to assign duties above Ch8 to the APM, my servos go nuts. Maybe it's me. The advanced user items such as channel mapping are not that well explained IMO.

Would you mind updating the Bixler param file to reflect the latest options and remove old options (ex. manual level)

BTW.. thanks much for the great improvements and timely updates.   You're doing a great thing.

Hey Paul,

Thanks a ton for sharing your X8 param file...  I downloaded it a while ago and finally got my X8 back in the air this week.  I know its been a while since you posted this , but I imported [most of] it to my X8 and was very impressed at how much better it performed than it did with my previous settings that were no where near fine-tuned.  

I'm curious if you have your AUW handy?  My CoG is the same as yours, but I'm pretty heavy at 3.4kg and am wondering if at that weight I'll be able to get descent in full turn to minimize before hitting the soft ceiling of 1.4 on PTCH2SRV_RLL.  It's already at 1.3 from your param file, and I don't yet know how much increments of 0.01 impact this, but hope to find out this weekend.  Anyways, if you have any additional tips, let me know.  I have the tuning guides printed and ready to take to the field, but this thing is so close right now that I'm hesitant to mess with anything drastic or even start from the beginning; an attempt to start from scratch with it caused a deathroll (my own fault for going too slow in windy conditions), but nothing a little hotglue couldn't cure.

If you're interested:

Skywalker X-8 AUW 3394g
Power: Hyperion HS3026-1210 with Atlas 90A ESC, APC 13x5.5E
Battery: 2 x Nanotech 4S 5000 (Parallel) with 12v ubec for Video and 5v ubec for output rail on APM



btw if you're interested, the DR is in the attached tlog at about 83%.  I also threw in the rlog and dataflash.

It seems that there is still a lack of clarity on this question.
Does APM have access and control of channels 9-12 for internal functions like RST_Mission. If so, how do we see this in mission planner?
Could we get a Dev to shine some light on this?


Today i tried a automatic flight. No luck. :(

I did a auto takeoff, than nothing. The plane climbed to the defined hight than did nothing but stabilised itself.

Never started to follow waypoint 2.

Do others have the same problem?

Am i doing something wrong?


Thanks Andrew. WRT "fixed RTL glide slope when starting above the target RTL altitude. Descent should now be smooth over long distances." Is the RTL glide slope a constant or can it be changed manually depending upon the airframe's polars? The original full scale DFS-230 glider had glide ratios of 1:11 empty and 1:18 fully loaded and I hope my 1:~10 aero-towed scale scratch build will have similar performance. Does the APM:Plane 2.74 release automatically adjust glide slope for maximum distance based on airspeed and barometer sensors data?




Why is the WP Radius limited to 127ft?
Auto takeoff to WP2 is working fine for me.

I've noticed that there's a ground altitude creep problem. Today I had an hour long flight/tuning session. During that time the home altitude changed by about 50 meters. So in the end the plane was actually flying at 50 AGL when it was supposed to be flying at 100 m AGL. So when I landed the plane MP showed it was at about 50 m elevation.

In the end the plane also made high speed pass 20-30 meters from the ground during loiter. Then I knew it was time to land. That's not fun at all.

After a reboot the ground alt was back to zero again. Is this kind of altitude creep normal and can I do anything to avoid it in the future?

Try letting the APM run for five mins to let the board warm up (and GPS fix), then reboot the board and/or do a Preflight Calibration from the Actions tab.
Heat will affect the baro.

Ok, I'll try that. I'm not sure it will completely solve the problem because while sitting on the ground before flight for 10-15 minutes the altitude reading had climbed 6 meters. I didin't recalibrate or reboot before launch. During the flight the ground rose another 40 meters. I think that preflight calibration wouldn't have avoided that 40 m ground altitude rise.

The temperature can change quite a few degrees during a longer flight.

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