HedgeTrimmer
First Officer
United States
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2wenty Posted at 2018-5-4 13:26
Yeah the video post before this was shot before the long video. The crash was the last thing that has happened. No more footage after that since it doesn't work anymore.
NON-WARRANTY PER DATA ANALYSIS. Compass interference FLY037 1. User took off from a metallic object causing immediate compass error. 2. At t=86s, unit started to drift. 3. At t=100s, user attempted to correct the course but unit drifted to obstacle. Force impact date: 4/22/18 Force impact GPS location: 34.3622815 -117.8660737 Activation date: 2017-01-23 SN: 08RDDBH00102Y9 Conclusion: Magnetic interference caused compass error. Unit drifted to obstacle and crashed. [Non warranty] Dear Customer, Unfortunately, damage that is not caused by a product malfunction or is out of the warranty period is not covered by DJI aftersales policy. We will either repair it or replace it with a product that's new or equivalent to new in both performance and reliability after payment has been received. For more information, please visit
NON-WARRANTY PER DATA ANALYSIS. Compass interference FLY037 1. User took off from a metallic object causing immediate compass error.
Disappointed that DJI makes such a statement, without offerring or explaining how DJI came to that conclusion.
From what you wrote, Mavic was 5-6 feet away from car, not on top of car. And that you had not had problems doing this before.
That leaves possibility that Mavic took off from (or very near) ferrous metal. Like say a man-hole cover.
Thought DJI would blame it on flying 30-minutes after sunset, being you said it was night when it happened.
By DJI going with 'Compass interference' as result of flying 'from a metallic object' and causing 'immediate compass error' it is leading to Catch-22.
There is no warning in Log file about Magnetic Interference prior to Compass Error.
I don't believe you saw any kind of warning about Magentic Interference prior to takeoff?
Log shows P-GPS mode starting at 5.0s after power-up and Mavic showing correct altitude of 0-feet.
If I remember correctly, you said you did not see any indication of Mavic going into ATTI mode, which fits with log.
According to manual, when compass experiences interference it is supposed to switch to ATTI mode, counter to what log continues to show till crash.
At 5.5s & 5.6s after power-up Mavic flight log shows Home Point Updated and Home Point Recorded.
You did say you tried RTH, but drone continued on its own accelerating.
There is no entry in log for RTH being activated.
Three possibilities: Compass Error did disabled GPS (despite log entry) thus disabling RTH, you did not hold RTH button on RC down long enough to activate,
or Mavic failed to receive / process RTH signal.
If compass error did disable RTH, at least drone should have stopped, and hovered on receiving at RTH.
First Compass Error, by log, came at 6.1s after power-up and Mavic is already 5.9 feet in air.
At that point, there is little that can be done. Being, Mavic is already starting to move up and away.
Even if a warning popped up on display at this point. Trying to determine why and what to do would be difficult.
Always easy to say what should have been done, knowing the why a day later, sitting behind keyboard, and sipping on .
I can not find anything in Mavic manual about checking Mavic's compass (pointer on map) against compass (rotating compass) displayed by GO-4, before liftoff.
Nor find anything in Mavic manual about checking GO-4 compass for magnetic interference as part of preparing for flight.
Given circumstances, it is doubtful lifting Mavic off ground and rotating it 90-degrees, and comparing Mavic's compass to SmartDevice's compass as shown
by GO-4 would have worked, unless you were at least back 12-feet from drone.
Being Compass Error warning in log didn't show up until Mavic was nearly 6-feet in air.
At 8.6s the Mavic appears to be starting to accelerate. Yaw is still stable at this point.
First indication that Mavic is turning (Yaw change) is at 10.1s. Good indication Interial sensors were working and IMU was too.
Between IMU working and GPS working, for DJI to ignore GPS because of Compass Error does not make sense.
Nor does it make any sense of Mavic to start accelerating out of control.
Granted the drone does not know which direction its nose is pointing.
However, drone could move short distance, compare its new location to old, and IMU information to workout how to return slowly back to starting point (or close too).
Assuming there were no GO-4 screen warnings, requiring acknowlegement - Catch-22 of this is.
DJI is saying their drone can experience magnetic interference that will at some point results in Compass Error, yet they can't detect it and warn drone pilot.
At same time DJI is expecting drone pilots to know in advance that there is magnetic interference.
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