I had a pretty exciting flight on the weekend. My plane with APM2.5 flew most of a circuit in Auto mode correctly, but towards the end it just flew off to sea!

I wanted to monitor the strength of the telemetry link by flying ever increasing loops. Each loop took me 300, 400, 500 and 600m away respectively. It flew the first loops fine but as it started the 600m loop it just wasn't quite on target. The GCS announced that it passed through two points on that loop, even though it passed 100m or more to the left of those points.

As it passed by the furthermost point it turned slightly to the right, and headed out to sea. Gasp. 

I had a strong telemetry link (RFD900) and the GCS map seemed reliable. The plane icon and yellow line both pointed to the next WP, but the other heading lines pointed out to sea. When I realized it wasn't coming back I used the RC radio to switch mode to RTL. The GCS text-to-speech announced the mode change, but it didn't change course. I thought all was lost as it was over the sea about 1.5km away.

In the GCS I tried the right click > Fly To Here command (I think it’s called Guided mode) but no change. My RC radio link started failing and I heard the GCS announcing the throttle failsafe modes (short = circle, long = RTL) as it drifted in and out of RC range. That didn’t help and it kept heading out to sea.

Finally it occurred to me to try flying back in Stabilize mode. I’d just do a right turn and watch the GCS map to see when it was tracking in the right direction. I held the RC radio up above my head, switched to Stabilize and put in a right turn for 5 sec or so and watched the GCS map. The RC radio was still drifting in and out of range but after a few attempts it started heading in the right direction.

After several minutes I could hear the plane, and soon after I could see it. The day was saved.


Now I want to know what went wrong. Can anyone help me? I’ve got complete logs but don’t know what to look for.

When I play back the log in Mission Planner, during the fly away the plane icon (and the heading in the HUD) is correctly pointing to the WP/home (a heading of 90 degrees to start with) but the plane is moving due North.

The Mag Declination reading shows .38 for the whole log replay. Xtrack error is mostly +/-15 as the plane flies correctly around the circuit, but it gets to around 200 during the fly away. There was almost no wind at all (at ground level).

I’ve attached the log file, the param files and a youtube link to a screen capture of the log playback. The APM2.5 uses firmware 2.66.


From about WP12 it’s getting more and more off track, after WP15 it just heads out to sea.

Any help appreciated.

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Hi again

My navigation gremlin is back. 

I was out this weekend attempting to fly a larger grid with a camera mounted and the navigation was a bit hit and miss. 

(The WP labels are a bit confusing, they appear above and to the right of the WP, in the scale of this image that puts them directly above the WP to the right.)

You can see from the purple trail that it was OK heading north. (At the far end it lost RC signal and went into short FS (circle mode). The circles weren't centred around the same spot, I'm not sure what that means. Also it got about twice as far last week before losing the RC signal).

Anyway on the way back it had a shocker missing WP11 by a lot, it did a late 90 degree turn to reach WP12, it was close to WP13 then headed off course for WP14.  It was obvious things weren't quite right so I switched to RLT (which worked well thankfully) and brought it back.

I tried again later with a much shorter grid and it did a pretty reasonable job.

Both flights are in the same log file, as attached. 

Any ideas? 

My log and parameter files are attached. Both flights in the same log file.

(Ignore the time it spent on it's back while I was mounting the camera.)

Those were the parameters loaded before the flight. COMPASS_LEARN was enabled, the compass offsets when I refreshed the parameters after the two flights were -52,-54,105 (compared with -10,-35,99 at the start).


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