BumblerBee
First Officer
Flight distance : 639764 ft
Norway
Offline
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And so the thing that I read much about, yet hoped would not befall me, happened to me today, on 32nd flight, after having spent 54km in the air in total.
The aircraft gave the dreaded "Compass error", "Yaw error", "Speed error" and switched to ATTI mode.
Here is the visualisation of the flight log at Phantomhelp: http://www.phantomhelp.com/LogViewer/LTPWIMXHH5JMHCH82160/#
And here are the logs from the app and the AC: https://drive.google.com/file/d/ ... Fk/view?usp=sharing
I was flying from a grassy field. I noticed the first anomaly during the pre-flight check - the AC arrow on the map was not pointing in the exactly same direction as the AC itself - the reading was a few degrees off. I opened the sensors menu to check the compass reading, and it showed both compasses as green, with compass #1 being in use (and having a value of about 180, while compass #2 had 6). I decided to carefully take off and everything seemed to be fine. Not entirely trusting the situation, I continued ascent from 10m hover while at the same time rotating the aircraft (taking an ascending panorama).
Then the errors started to roll. First a short burst of "Compass error" at 1m, while AC remained in GPS mode, then everythign seemed to be fine for a while, then again a short burst at 2:52, and then the final barrage of
"Speed error"
"Yaw error"
"Compass Error. Exit P-GPS Mode; Yaw Error", and finally
"In Flight,workingIMUencountersheading exception,please switch to atti mode if craft behave abnormally; Compass Error" at 3:22.
The last error with "please switch to atti mode if craft behave abnormally" is strangely worded as there is no way to switch it to ATTI mode, and besides it was already in ATTI mode for a whole second by the time of this error.
The wind was at about 4ms and Mavic began drifting. I started bringing it down, while correcting for the drift.
At 3:46 the aircraft switched back to P-GPS mode as if nothing happened. I continued to land manually at 4:15.
During the whole of the encounter 20 GPS/GLONASS sats were visible, I was in an open area and no cloud cover. I took a look at the AC log, an it seems that as one point Mavic simply stopped listening to the GPS sats.
Would it not be best for Mavic to continue using GPS heading in the cases when it disagrees with the compass heading? Why did not Mavic switch to the second compass if the reading on the first one were off?
Maybe some of the resident log gurus or DJI techs can take a look at the logs for any anomalies?
After landing I did a compass calibration (compass #1 went from 180 green to 8 green), took off from almost the same spot, then flew for good 17 minutes over the park, training on coordinated turns and not wanting to fly too far away after the incident, but all went smoothly.
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