DJI Mini 2 Flyaway/Crash Assistance

[Meta4]

The direction that you indicate is WSW (aprox 245 degrees). More likely the direction that I remember was 45 degrees to the right (300 degrees)

OK ... that confirms my suspicion.
The only thing I could think of that would cause the drone to zoom off the way you described is a Yaw Error.
Knowing that the drone was pointing in a different direction from the direction that would have shown on your screen confirms that this is what happened.

When you start up the drone, the gyro sensor takes its initial directional value from the compass sensor.
But if the compass sensor is deflected by a magnetic field, it will give incorrect data.
When the drone launches and climbs away from the magnetic field, it returns to read correctly, but the gyro sensor in the IMU continues to give incorrect directional data.
When the drone moves the data conflict between the compass and gyro sensors, that causes the problem.
The drone senses that it has drifted off course and tries to move back on course.
But the gyro data it's using puts the drone further away from where the flight controller thinks it should be.
This happens many times per second which causes the acceleration and curved flight path.

The way to prevent it happening is to check the direction of the drone icon on screen before launching and confirm that it is pointing the same direction as the real drone is.

The GPS issue appears to be a separate issue and having both issues together was confusing.
If the Russians have their jamming aimed in your direction again and you notice the number of sats start to fall like that .... try lowering the drone 10 metres or so and see if the numbers come back.
Most of the cases I've seen seem to be linked to a particular height and going below that makes things normal again.

 

[Bearded Sailor]

OK ... that confirms my suspicion.
The only thing I could think of that would cause the drone to zoom off the way you described is a Yaw Error.
Knowing that the drone was pointing in a different direction from the direction that would have shown on your screen confirms that this is what happened.

When you start up the drone, the gyro sensor takes its initial directional value from the compass sensor.
But if the compass sensor is deflected by a magnetic field, it will give incorrect data.
When the drone launches and climbs away from the magnetic field, it returns to read correctly, but the gyro sensor in the IMU continues to give incorrect directional data.
When the drone moves the data conflict between the compass and gyro sensors, that causes the problem.
The drone senses that it has drifted off course and tries to move back on course.
But the gyro data it's using puts the drone further away from where the flight controller thinks it should be.
This happens many times per second which causes the acceleration and curved flight path.

The way to prevent it happening is to check the direction of the drone icon on screen before launching and confirm that it is pointing the same direction as the real drone is.

The GPS issue appears to be a separate issue and having both issues together was confusing.
If the Russians have their jamming aimed in your direction again and you notice the number of sats start to fall like that .... try lowering the drone 10 metres or so and see if the numbers come back.
Most of the cases I've seen seem to be linked to a particular height and going below that makes things normal again.

Dear Meta4,
Thanks for your elaborate analyses and help.

In the 1st year after purchasing the drone I used to perform compass calibration every time I went on field. After that I become lazy and just check the software to see if compass calibration is required or not.

It is true that on the day of the crash I did not pay attention of the displayed radar and drone heading indicator because I worked with the drone in a very limited area, no more than 100 m away from Home Point and RC.

Have a nice weekend

 

[Meta4]

In the 1st year after purchasing the drone I used to perform compass calibration every time I went on field. After that I become lazy and just check the software to see if compass calibration is required or not.

Compass calibration is completely unrelated to the yaw error and would not have done anything to prevent it.
Compass calibration is almost never needed and certainly not required before a flight.

 

[rwilliam99]

The way to prevent it happening is to check the direction of the drone icon on screen before launching and confirm that it is pointing the same direction as the real drone is.

Thank you for this. While I've seen this advice before, I never understood WHY it was important. I've added it to my flight checklist.

 

[waynorth]

Thank you for this. While I've seen this advice before, I never understood WHY it was important. I've added it to my flight checklist.

This is one of the most important pre-flight checks, it is done in a few seconds. Many so-called fly aways would be avoided if every pilot did this quick check before take-off.
In addition I also check the sensors state in the app to see if the IMU and compass are "green" and ready.

 

[rwilliam99]

In addition I also check the sensors state in the app to see if the IMU and compass are "green" and ready.

Where is this "sensors state"? I don't recall seeing that in the DJI Fly app?

 

[waynorth]

Where is this "sensors state"? I don't recall seeing that in the DJI Fly app?

Ah, sorry I use Go4. Maybe it is called something else in Fly. It is a menu choice in the app that shows if the compass is deflected and you need to move the drone. It displays a line that goes from green to yellow to red. Green is OK. Another similar line shows if the IMU is in OK state. This is a very useful feature and I am sure DJI Fly has it somewhere.

 

[rwilliam99]

Ah, sorry I use Go4. Maybe it is called something else in Fly. It is a menu choice in the app that shows if the compass is deflected and you need to move the drone. It displays a line that goes from green to yellow to red. Green is OK. Another similar line shows if the IMU is in OK state. This is a very useful feature and I am sure DJI Fly has it somewhere.

This is all I could find:




It allows you to calibrate both of these - if it thinks they are wrong, it will ask you to calibrate them but otherwise they say "normal" (that has been my experience).

Anyone have any other info on this? I'm curious....