2 Fly Aways - Log Help

[Cutaway]

Not dismissing defective. My mavic is defective too in fact it is at DJI right now waiting to get repaired (though for different reasons) I would just hate for somebody else to have to go through the waiting game like I am having to go through. Also I am not dismissing that he is a pilot. I fly corporate jets for a living myself and some of the pilots that I fly with wouldn't begin to have an idea of how to fly or operate a mavic or any drone for that matter. Don't assume that we pilots are geniuses because that is far from true.

I am not trying to put pilots on some drone pedestal of know-it-all. I am giving them a tad more benefit of the doubt since they're trained in the art and science of flying including procedures and troubleshooting.

I just don't like to see "barber" shop talks on some of the responses (not dismissing all barber shop talk!). Drone on!

 

[Elvis]

Thought a little more about how the distortion could have been caused. I understand that you placed the Mavic on the ground outside your office facing east. The geoInclination at your location is 68.82 degrees. So it would like below on the left where the point of view is from behind the Mavic with both you and the Mavic pointing east. The geoMagnetic field comes from the left (north). Now, if a car were parked to the right of the Mavic the GMF would be distorted and would be coming from the right (south). This would make the Mavic think it is pointing west.View attachment 9211

The only car parked, was a Smart Car parked in the second parking spot to the north west of the drone, probably 15 feet away.

 

[SteelFlyer]

Certainly not an expert on this, but here's another thought. You said the light pole was plastic, but it still has wires running to it. Current moving through a wire creates a magnetic field at a right angle to the conductor. Probably far fetched but I suppose it might be possible for this field to create a very local magnetic anomaly.

 

[mmee]

I remember the phantoms would sometimes require degaussing of the compass sometimes to fix this issue. I haven't seen anything about degaussing the mavic compass but it might be worth a shot. @msinger have you seen anything about degaussing the Mavic?

 

[brantdw]

My old DJI F450 used to do this when the GPS was out of whack. Start drifting to one side. Turned out to be a bad GPS unit in the drone. Looks like the old DDI drift problem from years back. If you switch to ATTI mode does it stop drifting. I thing you need to send it back in for repairs before its lost forever.

 

[mfarris2]

I am not an DJI or Drone expert. But I am an engineer by trade. Some things to consider. Electrical wires in the light pole,....if energized will create an electrical (magnetic) field. Also any possible electrical wires in the building wall. Also,...are there any transformers near your location? Overhead wiring,....satellite feeds at the top of the building? Does the electrical to the building feed overhead or is it buried? Not saying this is your problem,....just a possibility to consider.

 

[mkp2020]

So, based on BudWalker's analysis our belief is magnetic interference is the root cause. Since magnetic force is measurable shouldn't we be able to measure the mag status at any given location before taking off? I'm thinking of situations such as when I am in the driver's seat of my car my phone compass never reads correctly. Is there a device that could tell you the location has too much instability there? Or is it possible a standard compass would read incorrectly from such locations? I would be perfectly willing to add an EMF test to my pre-flight check.

 

[stratos]

I took a quick look at this .DAT. In summary, the Mavic was launched from a geomagnnetically distorted location which led to a confused FC and erratic flight. There were two flights at 2017-3-21 13:22:14 local. . The first corresponds to the HealthyDrones flight that you provided. After landing it appears that the Mavic was moved without turning off the battery and then another, uneventful flight took place. But, your description said that the two front props were damaged in the first flight. Did you change them while walking to the second launch point?

Anyway, it appears that the first flight was launched from a geomagnetically distorted location. Possibly rebar in the concrete, or an underground pipe, etc. Before launch the incorrect magnetometer values cause the Yaw to be initialized incorrectly. After the Mavic launches and gets above the geomagnetically distortion the magnetometers become correct but Yaw, which gets it's value from the IMU, retains it's incorrect value. This can be seen here.
View attachment 9114
Initially, magYaw (the heading derived from the magnetometers) shows -91. After launch magYaw has changed to 62, the correct value, but Yaw is till -91.

The P3 would have declared a compass error, switched to ATTI, and let the pilot do the navigating. Maybe the Mavic should do the same, but, I've seen a couple of flights now where it remains in GPS_ATTI and tries to correct the problem. That can be seen here where magYaw is showing the Mavic turning in the direction that will align with the incorrect Yaw value. It never switched to ATTI mode. In other incidents like this where a video was available it's been verified the Mavic is actually turning although Yaw is constant.

Got all that?. The same thing probably happened in the first flight where the car roof caused a similar problem.

Jsut because your chart is amazing I would believe anything you said

 

[Dronebow]

Get DJI to review the logs. Something is not right and it doesn't sound like it's just a calibration issue.

How about your controller? Is it possible that your sticks are not centered or reading incorrectly?

 

[bucefalo]

guys that's what I tried to say when I had the only single problem with my mavic! as a newbie, weeks ago, I took off from a metal hatch on the ground.. before take off I checked the values of compass/imu all good! 5 seconds after take off the drone got crazy and I had no control for about 20 seconds! no crash cause luckily I was In a open space and then after that crazy ride the drone stop in middle air and I got back control! it was 100% my fault but I wonder as you do:
1) shouldn't I always have control also in this compass error?
2)if I have no control why the drone speed up and move faster (faster than when I had control..)

 

[BudWalker]

guys that's what I tried to say when I had the only single problem with my mavic! as a newbie, weeks ago, I took off from a metal hatch on the ground.. before take off I checked the values of compass/imu all good! 5 seconds after take off the drone got crazy and I had no control for about 20 seconds! no crash cause luckily I was In a open space and then after that crazy ride the drone stop in middle air and I got back control! it was 100% my fault but I wonder as you do:
1) shouldn't I always have control also in this compass error?
2)if I have no control why the drone speed up and move faster (faster than when I had control..)

Take a look at post #37 in this thread. Maybe that will answer your questions.

 

[BudWalker]

So, based on BudWalker's analysis our belief is magnetic interference is the root cause. Since magnetic force is measurable shouldn't we be able to measure the mag status at any given location before taking off? I'm thinking of situations such as when I am in the driver's seat of my car my phone compass never reads correctly. Is there a device that could tell you the location has too much instability there? Or is it possible a standard compass would read incorrectly from such locations? I would be perfectly willing to add an EMF test to my pre-flight check.

It's a tough problem. As I described in post #37 the only way to detect this situation is by the pilot first visually determining the AC orientation. And, then comparing that with the AC orientation presented by the Go App.