RTL: No Throttle when trying to climb up to target altitude

Today I continued to test APM. I was doing cruise and Loiter at 30m. RTL Target altitude is 75m. When switching from Loiter to RTL, the plane starts to pull aggressively Elevator and tries to climb to target Level and throttles DOWN instead of going UP to climb !!! Which leads to stall !!!

I checked throttle direction, but the throttle is set right for Cruise and Loiter.

Any help is highly appreciated.

Post .log , or it didn’t happen :slight_smile:


It probably did happen. I posted on this same issue a few weeks back, and got quietly ignored. Here’s my thread with log. I’ve been through the log and it looks a lot like a FW problem. viewtopic.php?f=96&t=6191

Almost midnight here, a quick glance, shows taht your VCC goes down to 4.83v a few times, but worst of all, is that I do not see a single RTL logged, but i see “initialising” 5 times !

What autopilot HW are you using? The apm 1 Vcc doesn’t get logged accurately.


BTW you can see what I mean when you select ModeNO (RTL=11, Loiter=12) and plot throttle Output against it. Have a look at minute 11. Mode Switch to RTL and throttle goes to Zero.

Initialising = Hard Reboot ? Not good at all, this would mean new RTL-Location and new gyro initilisiation and temp. loss of control, right ? Or could this come from the automatic cpmass calibration which was enabled ?

Appreciate that you take the time.

Hans, do you remember your flight Situation ? I flew at 30 meters and the airplane had a target RTL altitude of 75m. I could understand that this is a specific test-Situation. So, we did not used the Default neg value to stay at Level and we did not go down from a high travel height, but Need to go up…maybe this is a Special condition which have not been tested yet ?

Yes, I needed to climb as well. Have a read of the post I linked. That describes it in detail. I can’t have a look at your log until tomorrow, because I’m travelling at the moment.

I have found it: CENTIMETERS !!! Shit, this is embarrasing.

I have specified 75 as TargetAltitude…thought it is meters, but found it is defined as centimeters !!! So, with 7500 it now throttles and goes up !!!

The only weird Thing is, when I engage RTL, it does the follwing in a consistent way:

  • Ignore the command for 10 sec and circle around (maybe to gain height ?)
  • fly to a direction, but not the Home direction
  • after 20 sec, correct the direction towards more to the home direction
  • after another 20 sec. next direction-correction
  • finally, arrives home
  • circles are not consistent: Somestime circles in big, sometime in VERY small circles and Speeds up quiet a bit, where you feel it takes the max angle and is near to stall…I gues it has something to do with the way it handles internally waypoints ? Any hints ?

This is all with airspeed sensor off. Next round will be to calibrate it again and see if it will make things better or worse.


  • the circle is there by design. see FS_SHORT_ACTN and :FS_LONG_ACTN
  • check your compass.

I will…but you made me now nervous with this initializing Thing…and why it has been there 5 times…can you comment this ? No Need to worry or big issue ?

It seems to be a Mission Planner bug, it lists mode 12 as “initializing” - while arduplane source clearly defines 12 as Loiter, and 16 as as initialising.

That is a good hint, will check this with the2.0 version…

compass issue confirmed and erased:

I originally tested the compass…everything was fine. Than I found in the parameters list “external compass” and as my compass is on the gps enabled it…well…this messed the compass orientation up. should have been a warning that this is changing the orientation…but as well my fault not having checked this again.

So, I am looking VERY forward to tomorrows flight with a compass withright orientation and see what this will do to flight stability…smile