2 Fly Aways - Log Help

[Elvis]

You can also make a screen recording of your flight's playback in the GO App. Make sure to tap the button to show the stick input overlays, too.

Inside the videoCache directory, I see zero files. I do have AirShou installed so maybe I can replay the flight and record it? I have never done this, but I will look in the GoApp now to see if I can figure this out.

 

[Elvis]

You can also make a screen recording of your flight's playback in the GO App. Make sure to tap the button to show the stick input overlays, too.

I am in the DjiGo app. Under Editor / Videos, there are zero videos. Is there somewhere else these videos are located?

 

[Anthonyk]

In dji 4 go to top right of screen three bars tap on these and it will show an option to flight records.

 

[Elvis]

Here is the dropbox link for the DAT file that is on the Ipad. Someone let me know if a DAT file off of the Mavic itself is required.

Dropbox - 2017-03-21_13-18-28_FLY168.DAT

 

[BudWalker]

Here is the dropbox link for the DAT file that is on the Ipad. Someone let me know if a DAT file off of the Mavic itself is required.

Dropbox - 2017-03-21_13-18-28_FLY168.DAT

The .DAT files you want are on the Mavic itself. Look here to see how to retrieve them. There is a section about picking the right .DAT.

 

[Elvis]

I tried to install DJI Assistant onto 2 computers Windows 7 and Win 10 and both gave me issues about unsigned drivers from DJI. It seems like I am still able to get into the software. I can't obtain anything from the Flight Data tab. However, on Data Upload, it appears i can save DAT files if I click Save To Local. Would this be the correct files to obtain?

This might be the file in question that I obtained from Data Upload inside DJI assistant - Dropbox - DJI_ASSISTANT_EXPORT_FILE_2017-03-22_15-55-47.DAT

 

[Elvis]

Here is the video recording of the flight with stick controls. You will see right after take-off, I realize something is very wrong and left-stick down to land. The mavic starts moving away from me faster and faster and rotating. I then push both sticks to inside left to try to "kill" the motors. It was close to the ground so I figured killing the motors would be better than it speeding up and hitting something else. The motors never died, but it did end up landing at a very hard attitude angle.

What might be the problem here? Here is the video link - Dropbox - ELVIS-OutOfControl.MP4

 

[Strafe1]

Looks like you took off close to a building, from a parking lot with rebar likely in the concrete, and before HP was locked? Perhaps other interferences in play also, like WiFi? These are guesses. Looks like your drone is facing towards the building on your map. If it wasn't facing this direction, could be telling that compass is already confused.

 

[Elvis]

Looks like you took off close to a building, from a parking lot with rebar likely in the concrete, and before HP was locked? Perhaps other interferences in play also, like WiFi? These are guesses. Looks like your drone is facing towards the building on your map. If it wasn't facing this direction, could be telling that compass is already confused.

I was pointing away from the building, not towards it, so maybe you are correct. I don't think there is any rebar in the parking lot at all. It is just concrete. And I sat the drone about 15 feet away from the building with a wide open field behind. I did not get a notice to "recalibate compass" as sometimes I do. From reading, I thought you should only recalibrate the compass when it says to recalibrate it.

EVEN IF the compass was out of whack, it had a GPS lock. Shouldn't the mavic know it is drifting / accelerating based on the GPS lock data? Who can look at the DAT file posted above? Maybe that would shed some light?

This has happened twice now. I am headed to the ocean in Bahamas in 2 weeks and don't want this to happen for a 3rd time. If it crashes in the ocean I am out of luck....

 

[m0j0]

Today was the second time this happened. Hoping someone could look at my logs and tell me if there is something wrong with my Mavic.

First episode: I sat the Mavic on top of my car sun roof and took off after GPS lock. As soon as the mavic was airborne, it immediately started to drift quicker and quicker in a large circle away from me.
Any help appreciated.

Thats the toilet bowl effect (TBE) and indicative of compass problems. The problem could be a result of taking off from the top of your vehicle which is a no no.

I thought maybe the drone switched into ATTI mode and the wind took it away. I replaced all 4 props, and did not have a problem again until today.

That is possible that it switched to ATTI monde. Which could be caused by taking off from the car. As soon as you get away from the car the compass will show the error and cause the Mavic to turn off the GPS.

Second episode: I sat the mavic on the ground by my office like I do most flights. Waited for a GPS lock and took off. This was my 2nd flight of the day, with no problems with my first flight. As before, as soon as the mavic took off it started to immediately drift faster and faster away from me. I looked down this time and I still saw the Green GPS flight mode, so GPS could not have been the issue. I immediately tried to control and land the mavic. Luckily there were no rocks this time, and I just damaged the front two props. The mavic once again took on a very odd attitude leaning forward and started to drift in a circular fashion away from me quicker and quicker.

I turned off the mavic and turned it on and had no problems on a short test flight after this.

I am going to the Bahamas in 2 weeks and I am afraid it is going to do the same thing and I am going to lose it in the ocean...

My gut is telling me now that maybe there is an intermittent problem with an internal sensor or gyro?

I have been flying drones for some time and have my pilot's license and am very confident this is not user error.

I have copied over to my desktop FlightRecords folder. Is it possible someone could take a look at this and maybe see if they could tell me what the problem was?

Any help appreciated.

I would look to the compass. Get a clean calibration - one in an area where there is no underground metal. Do not do a calibration on concrete... it has rebar in it. Everything you are talking about makes me believe you have a bad compass calibration. Get a good calibration and stay away from large metal objects which will confuse the compass.

 

[m0j0]

Especially the fact that most either missed or dismissed that you're a pilot. Bummed to hear about your trouble. Good luck.

What does being a pilot have to do with any of this? The TBE is a common indicator of a compass error.

 

[BudWalker]

I was pointing away from the building, not towards it, so maybe you are correct. I don't think there is any rebar in the parking lot at all. It is just concrete. And I sat the drone about 15 feet away from the building with a wide open field behind. I did not get a notice to "recalibate compass" as sometimes I do. From reading, I thought you should only recalibrate the compass when it says to recalibrate it.

EVEN IF the compass was out of whack, it had a GPS lock. Shouldn't the mavic know it is drifting / accelerating based on the GPS lock data? Who can look at the DAT file posted above? Maybe that would shed some light?

This has happened twice now. I am headed to the ocean in Bahamas in 2 weeks and don't want this to happen for a 3rd time. If it crashes in the ocean I am out of luck....

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.

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.

 

[JLane]

Without looking at the DAT file... even in HD you can see the Mavic swap to ATTI as soon as it left the ground.

I think BudWalker has now done a pretty good analysis from the .dat file, but just FYI, the flight log on HD does not show it was in ATTI mode. In the log files "GPS_Atti" means GPS mode, not ATTI. Basically, what we refer to as GPS mode or P-Mode is ATTI mode plus GPS (all the IMU sensors required for maintaining level attitude, plus GPS for positioning).

 

[m0j0]

Yep Agreed BudWalker's a genius. It is as expected. Compass error.. which could have been caused by taking off from the car.

This is what I categorize as a give away.

 

[Elvis]

Fantastic analysis Bud!!

The first time this happened (taking off from car) was a few months ago. I have calibrated compass numerous times since then.

And then it happened again, from the parking lot.. I'm not sure why it doesn't switch out out of GPS mode and let me hand fly it...

It was impossible to control both times..

Is it possible the compass is malfunctioning / faulty, or is it definitely interference??

The Mavic should not stay in GPS mode and become impossible to control with just some compass interference and no warning?! While I understand the first occurrence of taking off from the car was a bad idea (it was extremely cold outside), the second occurrence with the mavic's reaction is scary...

 

[JLane]

The Mavic should not stay in GPS mode and become impossible to control with just some compass interference and no warning?! While I understand the first occurrence of taking off from the car was a bad idea (it was extremely cold outside), the second occurrence with the mavic's reaction is scary...

You're right, the aircraft should respond to control inputs at all times. However, this type of thing unfortunately seems to be not uncommon with the Mavic. There have been several reports of people claiming they were unable to control their Mavic, usually when it suddenly drops into ATTI mode, but so far DJI doesn't seem to acknowledge that there's any problem. Well, not explicitly, anyway. There was a case just in the past week or so where a guy's Mavic flew off out of his control and crashed. Luckily he was eventually able to find it, and sent it to DJI for analysis. He just reported back today saying that DJI agreed it was not his fault, and that they'll replace it under warranty. They didn't really give any explanation, though. So they clearly must know that something is wrong, but they're not saying anything about it.

If I were you, I'd send the logs to DJI and ask for a full analysis and explanation, and an assurance that they're doing something to prevent this kind of uncontrollable flight in the future.

 

[BudWalker]

Fantastic analysis Bud!!

The first time this happened (taking off from car) was a few months ago. I have calibrated compass numerous times since then.

And then it happened again, from the parking lot.. I'm not sure why it doesn't switch out out of GPS mode and let me hand fly it...

It was impossible to control both times..

Is it possible the compass is malfunctioning / faulty, or is it definitely interference??

The Mavic should not stay in GPS mode and become impossible to control with just some compass interference and no warning?! While I understand the first occurrence of taking off from the car was a bad idea (it was extremely cold outside), the second occurrence with the mavic's reaction is scary...

This isn't a compass calibration issue. So calibrating the compass won't help with these situations.

Unfortunately, it can be difficult to know this situation exists prior to launch. The geomagnetic field is distorted and it's easy for the field's strength to be close to normal while the direction is incorrect. When you look at the magnetometer info in the Go App what it's telling you is based on the field strength; it can't know that the field direction is wrong. The only way for the pilot to know this situation exists is to visually look at the AC and determine it's heading relative to magnetic north. Then compare that with the heading presented by the Go App display; i.e. which direction is the red triangle pointing. Do you recall the AC's heading prior to launch. I'll bet that you pointed it away from your office pointing 72 degrees. If you look on the replay you should see the initial heading -91 degrees

Having said this let me say that I never make this visual check; it's too much of a hassle. But, having seen several of these events has caused me to always think about the possibility of geomagnetic distortion at the launch site. My flying buddy never thinks about this though; and is probably tired of hearing me tell him to worry about it.

This type of compass error can't be directly measured. E.g., it's not like the magnetometers quit altogether. In this particular situation all the AC really knows is that Yaw and magYaw don't agree. It can't know which one is correct. Anyway, the crux is that this type of compass error has to be inferred which then admits the possibility of mistakes. Either a false positive, or not detecting a compass error when one exists. In the case of the P3, it seems that with every firmware update more false positives would occur. The P3 would detect an error, switch to ATTI, and then expect the pilot to do the navigating. With the Mavic it seems the strategy is to reconcile these errors by remaining in GPS_ATTI and continuing to navigate. Doesn't always work so well as you can see. Maybe this strategy will improve with future firmwares.

The Mavic was responding to your control inputs. But, it was also responding to it's own navigation directives. I.e., you and the Mavic were both controlling it. Maybe a distinction without a difference since you may not have had enough control to navigate it effectively.

As to the question of a possible compass malfunction. IMHO the odds are very low. Such a malfunction would have to resolve itself just as the Mavic is leaving the launch site.

 

[R1Mavic]

I experienced this yesterday. When I went into the settings, there was a vision sensor that said "error" in red. I hit calibrate and it had me move the drone in this square motion that never removed the error. Along with this when it took off it said something about not being able to go over 16ft.
As a beginner I gotta say, so much is popping up on screen that I clear not fully understanding why I'm getting it.

 

[Elvis]

This isn't a compass calibration issue. So calibrating the compass won't help with these situations.

Unfortunately, it can be difficult to know this situation exists prior to launch. The geomagnetic field is distorted and it's easy for the field's strength to be close to normal while the direction is incorrect. When you look at the magnetometer info in the Go App what it's telling you is based on the field strength; it can't know that the field direction is wrong. The only way for the pilot to know this situation exists is to visually look at the AC and determine it's heading relative to magnetic north. Then compare that with the heading presented by the Go App display; i.e. which direction is the red triangle pointing. Do you recall the AC's heading prior to launch. I'll bet that you pointed it away from your office pointing 72 degrees. If you look on the replay you should see the initial heading -91 degrees

Having said this let me say that I never make this visual check; it's too much of a hassle. But, having seen several of these events has caused me to always think about the possibility of geomagnetic distortion at the launch site. My flying buddy never thinks about this though; and is probably tired of hearing me tell him to worry about it.

This type of compass error can't be directly measured. E.g., it's not like the magnetometers quit altogether. In this particular situation all the AC really knows is that Yaw and magYaw don't agree. It can't know which one is correct. Anyway, the crux is that this type of compass error has to be inferred which then admits the possibility of mistakes. Either a false positive, or not detecting a compass error when one exists. In the case of the P3, it seems that with every firmware update more false positives would occur. The P3 would detect an error, switch to ATTI, and then expect the pilot to do the navigating. With the Mavic it seems the strategy is to reconcile these errors by remaining in GPS_ATTI and continuing to navigate. Doesn't always work so well as you can see. Maybe this strategy will improve with future firmwares.

The Mavic was responding to your control inputs. But, it was also responding to it's own navigation directives. I.e., you and the Mavic were both controlling it. Maybe a distinction without a difference since you may not have had enough control to navigate it effectively.

As to the question of a possible compass malfunction. IMHO the odds are very low. Such a malfunction would have to resolve itself just as the Mavic is leaving the launch site.

Bud, everything you say seems right on. The triangle was pointing at my building instead of pointing out at the field like it usually does. There is a light pole on the sidewalk nearby about 6 feet away. I thought maybe this pole could be doing the interference, but I checked today and the pole is not metal, but hard plastic. Also the building is a 2 story building with brick at the bottom and the rest of the building is stucco. I was about 15 - 20ft away from the building, so I don't think the building should be causing any interference. The parking lot is not concrete, it is asphalt, and I am 99% sure there is no rebar below. Maybe there are some utilities underground causing the interference, but I don't think there is any rebar or heavy metal in the near vicinity.

Now that I think about it, not on this flight but on a few previous, I do remember seeing "compass redundancy error" a few times on the screen during previous flights. I wonder if 1 of the 2 compasses is having some problems. If it happens again, I think I will seek the help of DJI for possible repair. And the number one lesson learned is I will definitely try to make sure I look and see where the triangle is pointing before I takeoff from now on.

 

[BudWalker]

Bud, everything you say seems right on. The triangle was pointing at my building instead of pointing out at the field like it usually does. There is a light pole on the sidewalk nearby about 6 feet away. I thought maybe this pole could be doing the interference, but I checked today and the pole is not metal, but hard plastic. Also the building is a 2 story building with brick at the bottom and the rest of the building is stucco. I was about 15 - 20ft away from the building, so I don't think the building should be causing any interference. The parking lot is not concrete, it is asphalt, and I am 99% sure there is no rebar below. Maybe there are some utilities underground causing the interference, but I don't think there is any rebar or heavy metal in the near vicinity.

Now that I think about it, not on this flight but on a few previous, I do remember seeing "compass redundancy error" a few times on the screen during previous flights. I wonder if 1 of the 2 compasses is having some problems. If it happens again, I think I will seek the help of DJI for possible repair. And the number one lesson learned is I will definitely try to make sure I look and see where the triangle is pointing before I takeoff from now on.

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.