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Mavic 2 zoom flyaway and crash seconds after take-off

jdemirhan1

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Hi all

I have included the flight log for the info but last night I set up to fly my drone in Newcastle. I had 11 - 12 locked gps' and the home point was recorded. I did a compass calibration right before it too.
I took off, and flew forwards towards the river then as I let go of the sticks for it to hover, it kept moving sideways to its right, it got faster as it pivoted my location and I did an emergency stop as it got over a walk way onto a hill to minimise the chances of injury to someone.
 

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Meta4

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Hi all

I have included the flight log for the info but last night I set up to fly my drone in Newcastle. I had 11 - 12 locked gps' and the home point was recorded. I did a compass calibration right before it too.
Your incident has all the indications of one caused by a yaw error.
Why did you calibrate the compass?
What was the surface you launched from?
What direction was the drone facing when it was on the ground after powering up?
Was it northeast or something different?
 

jdemirhan1

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Your incident has all the indications of one caused by a yaw error.
Why did you calibrate the compass?
What was the surface you launched from?
What direction was the drone facing when it was on the ground after powering up?
Was it northeast or something different?
The compass was calibrated as it was prompted as a requirement when I powered on.
The surface was concrete walkway.
The drone was facing south, away from me towards the river.
 

Meta4

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The compass was calibrated as it was prompted as a requirement when I powered on.
The surface was concrete walkway.
The drone was facing south, away from me towards the river.
Yes ... that was a yaw error.
There was nothing wrong with the compass and recalibrating the compass couldn't "fix" the problem.
Your compass was warning that it detected a magnetic influence where you launched from (it will have been steel in the reinforced concrete).
The solution would have been to power off and move away from the problem.

Your compass was deflected and the IMU took this incorrect heading information when it initialised.
You launched, moved away from the magnetic influence and the compass came back to normal, but the IMU gyro sensor can't and now there's a big data conflict between the two directional sensors.
That's what caused the incident.

Launching from reinforced concrete is never a good idea.
When you think the drone is telling you to calibrate the compass, it almost never is ... just warning you of a potential problem if you launch there
 

jdemirhan1

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Yes ... that was a yaw error.
There was nothing wrong with the compass and recalibrating the compass couldn't "fix" the problem.
Your compass was warning that it detected a magnetic influence where you launched from (it will have been steel in the reinforced concrete).
The solution would have been to power off and move away from the problem.

Your compass was deflected and the IMU took this incorrect heading information when it initialised.
You launched, moved away from the magnetic influence and the compass came back to normal, but the IMU gyro sensor can't and now there's a big data conflict between the two directional sensors.
That's what caused the incident.

Launching from reinforced concrete is never a good idea.
When you think the drone is telling you to calibrate the compass, it almost never is ... just warning you of a potential problem if you launch there
I'll make sure to avoid concrete and check the compass readings, IMU readings and aircraft heading on the map in relation to its real heading.
So everytime I get a compass calibration error, so I just have to switch off and move to a different location?
I've nearly always had a calibration prompt prior to most flights. When do I actually need to calibrate the compass?
 

Meta4

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So everytime I get a compass calibration error, so I just have to switch off and move to a different location?
That's right.
I've nearly always had a calibration prompt prior to most flights.
Are you launching from concrete or within a foot or two of visible steel objects?
When do I actually need to calibrate the compass?
Never ... or almost never.
When it's really needed is after rebuilding, adding or removing something from the drone.
 

slup

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Yep ... a clear yaw error due to powering on the drone in magnetic interference.

From time to time I throw in my "Newbie Card" to greet newcomers in the forums Pilot Check In section ... below 3 important points from that card regarding

-How to power on in order to avoid this kind of incidents
-How to check that everything is OK before take-off
-How to treat compass calibration prompts in the app

Power on in the right order ... First power on your RC & start the app ... after that, power on the drone (& do it on the spot you're going to take off from). Reverse order to shut down.

Preferably power on the drone keeping it horizontal in your out stretched hand (without watches, rings or other magnetic objects) … once the live view have turned up in your mobile device you can put it on ground for take-off. (This supports the point below …)

Before take-off ALWAYS ... add in one very easy check to avoid a really scary event coming from accidentally launching from a magnetic disturbed place with following flyaway at height in an uncontrollable circular or straight flight path. After powering on your drone, connected to your RC/app & placed it in the take-off spot ... but before lift-off, ALWAYS check that the drone icon on the map in your app is pointing equal in relation to other objects in the map as the drone does in reality ... if not, abort launch attempt, POWER DOWN & move away, power up again and repeat.

Don't go & calibrate everything on a regularly basis ... why fix things that are working, it's just a higher risk that you by mistake calibrate your compass in a magnetic disturbed area & the drone goes haywire 10 meters up in the air. Calibrate IMU + compass according to user manual, keep away from magnetic things like cars, metal tables & reinforced concrete at take-off & compass calibrations. If the app recommend a compass calibration first try another launch spot on a far distance from the first ... if calibration still is recommended by the app do it, but only then.


You have a full "Newbie Card" here if you want it all --> Newby - Just joined - Hi everyone. Look forward to being part of the group and learning a lot more about droning. I am new to droning and own a 2s.

...Your compass was deflected and the IMU took this incorrect heading information when it initialised.
You launched, moved away from the magnetic influence and the compass came back to normal, but the IMU gyro sensor can't and now there's a big data conflict between the two directional sensors.
That's what caused the incident.
Just a smaller clarification what actually happens & why the drone fly's away ...

The data conflict between the compass & IMU as such isn't the problem ... you can have situations with bigger deviations between these 2 during flight that doesn't start off fly away's. One example is when you shortly fly into magnetic disturbance (close to a big steel object perhaps), this will deflect the compass but the IMU will not immediately follow ... so nothing will happen, this as it's the IMU that handles yaw during flight, not the compass. Staying to long in the interference will eventually cause problems as the compass will slowly feed in adjustments to the IMU ... which over time will cause a yaw error.

What happens & what's the cause of the rapid fly away is instead that the IMU have wrong info about the heading direction from start. When the IMU needs to hold position due to drifts (drone affected by wind for instance) it will command the wrong motors to take the drone back to it's intended position. This leads to that the positional error grows instead of becoming smaller ... & the IMU tries again & again more & more forceful ... with the wrong motors and the drone speeds away often exceeding both specified tilt angel & max air speed.
 
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KB9Radio

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The compass was calibrated as it was prompted as a requirement when I powered on.
The surface was concrete walkway.
The drone was facing south, away from me towards the river.
When I first started flying my DJI it often told me to calibrate the compass or move to a different location. A solid concrete pad just seemed like a great spot to launch from. After learning to stay away from concrete which is usually reinforced with rebar, I don't think I have ever did a compass calibration since. I picked up a large (about 48") launch pad hoop that I use all the time to launch from the grass/dirt. It works very well, and I have never had an issue or had to calibrate since.
 
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