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How to protest a DJI crash analysis?

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Jan 7, 2018
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#1
My seven month old Mavic Pro crashed and broke off a rear motor. I sent it to DJI for repair and their analysis was pilot error. (no warranty) Here are the details. I launched the ac and once airborne I noticed the gimbal was not horizontal so I landed and did a shutdown on the ac. Restarted so that it would do a gimbal calibration again. I then did a compass calibration and set the bird down on concrete and waited for gps lock and home point record. When I launched the drone instead of rising up to the normal position it rose up about three or four feet and immediately started to fly off sideways with no stick inputs. So my first reaction was to stop the motors with full down and inward stick control which seemed to have no effect. The drone continued a sideways skid across the yard and smacked into the curb breaking off the rear motor.

What should I do?
 

Dave A

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#3
Sorry to hear about your crash. Really hard to say what happened without seeing your flight logs. There are people here who know how to analyze then with great accuracy. You have to be really careful when taking off from concrete because usually there is steel reinforcing withing it that can throw the compass off.
 
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msinger

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#4
I then did a compass calibration and set the bird down on concrete and waited for gps lock and home point record. When I launched the drone instead of rising up to the normal position it rose up about three or four feet and immediately started to fly off sideways with no stick inputs.
The concrete could have contained rebar. If that was the case, it could have negatively affected the compass.

Please upload your TXT flight log here and post a link back here. You'll find instructions for locating your TXT flight log at that link. We can take a look and let you know what we think happened.
 

JMF

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#5
Stomp your feet and scream hysterically, if DJI says it's not covered, it's not covered.
 
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james_mav

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#8
I've seen a number of people post the same crash scenario on this board. This is a very dangerous occurrence & it seems like DJI should put something in the software which would prevent the Mavic from taking off when the compass is so out of whack.
 
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beachcombing

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#11
My seven month old Mavic Pro crashed and broke off a rear motor. I sent it to DJI for repair and their analysis was pilot error. (no warranty) Here are the details. I launched the ac and once airborne I noticed the gimbal was not horizontal so I landed and did a shutdown on the ac. Restarted so that it would do a gimbal calibration again. I then did a compass calibration and set the bird down on concrete and waited for gps lock and home point record. When I launched the drone instead of rising up to the normal position it rose up about three or four feet and immediately started to fly off sideways with no stick inputs. So my first reaction was to stop the motors with full down and inward stick control which seemed to have no effect. The drone continued a sideways skid across the yard and smacked into the curb breaking off the rear motor.

What should I do?
I'm curious why you did a compass calibration.
 

7thstring

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#12
Good point. If it ain't broken don't fix it. Why calibrate? If I get a calibration warning and I'm close to metal objects or concrete supposedly hiding rebar, I just hand launch and the calibration warning disappears. If you try and recalibrate due to a magnetisation in the same conditions who caused it, you'll fly with a totally wrong compass for the rest of the flight.

From what I keep reading in all the problematic situations reported, it looks like hand launch and catch are heavily underestimated.
 

Kilrah

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#14
This is a very dangerous occurrence & it seems like DJI should put something in the software which would prevent the Mavic from taking off when the compass is so out of whack.
It already does when the mod value is unrealistic. But it is physically impossible to detect certain compass error situations on the ground.
 

7thstring

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#15
I guess it depends on who you ask. Hand launch will usually not help with compass errors.
Not so sure. Everytime I got asked to recalibrate it was because I was launching from the ground, on all sorts of metal objects. Recalibrating never worked (obviously, as you recalibrate at worst 1.5 meters higher than where the issue occurred in the first place), while rebooting and hand launching always did.

Still there is something that puzzles me... the compass should only be affecting the yaw/direction, not cause the drone to go sideways on a complete fly-away. That seems more of a IMU / gyroscope / etc issue or a combination of many factors. Certainly has to do with magnetic interference.
 

Thunderdrones

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#16
Not so sure. Everytime I got asked to recalibrate it was because I was launching from the ground, on all sorts of metal objects. Recalibrating never worked (obviously, as you recalibrate at worst 1.5 meters higher than where the issue occurred in the first place), while rebooting and hand launching always did.

Still there is something that puzzles me... the compass should only be affecting the yaw/direction, not cause the drone to go sideways on a complete fly-away. That seems more of a IMU / gyroscope / etc issue or a combination of many factors. Certainly has to do with magnetic interference.
Usually a compass error midair will cause the toilet bowl effect. Big, uncontrollable, sweeping circles, possibly leading to a catastrophic event. Here is a related thread:

TBE-what to do if it happens?
 
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7thstring

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#17
Thanks very useful link. Wonder why DJI don't allow disabling GPS to force Vision and ATTI.

With vision it should be able to self-recalibrate by understanding that the action performed don't achieve the expected results but so should happen in GPS as well. It's a matter of prioritization of inputs... if the compass is considered to be more reliable, this a priority, that. GPS or vision, well... they should allow us to bypass it.
 

Simmo

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#19
I think we need a bit more help with this one. The cause was because the AC was in Atti mode due to gps health (due to the compass error??) and drifted. The AC was responding correctly to control stick inputs. Unfortunately pilot error is the correct call. Untitled.jpg
 
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#20
I think we need a bit more help with this one. The cause was because the AC was in Atti mode due to gps health (due to the compass error??) and drifted. The AC was responding correctly to control stick inputs. Unfortunately pilot error is the correct call. View attachment 42456
Thanks for analyzing for me. I think the biggest thing I've learned is not to launch off of concrete. I'm not sure if it ever goes zooming off on it's own again in the future if I can leave my hands off the controls rather than trying to save it.
 

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