Sudden crash: my fault or DJI's

[MavicCF]

Thanks Cyberpower678, not what I hoped to hear of course but thank you very much for analyzing the logs! It must have been a small bird or something. Thanks again! Now all I need is more money. -CF

 

[Cyberpower678]

I'm inviting @Robbyg and @BudWalker, who are also very experienced with flight analysis, to provide input I may have missed or misread.

 

[Cyberpower678]

Thanks Cyberpower678, not what I hoped to hear of course but thank you very much for analyzing the logs! It must have been a small bird or something. Thanks again! Now all I need is more money. -CF

You can try and submit a case to DJI and see what they say about your flight and if it is covered under warranty.

 

[MavicCF]

You can try and submit a case to DJI and see what they say about your flight and if it is covered under warranty.

Will definitely try! If they don't I might have Thunderdrones take a crack at repair.-CF

 

[Robbyg]

I'm inviting @Robbyg and @BudWalker, who are also very experienced with flight analysis, to provide input I may have missed or misread.

Which one of the files is the correct one Cyber?

Rob

 

[Cyberpower678]

Which one of the files is the correct one Cyber?

Rob

The largest one with the lowest number, I believe.

 

[Cut.Aussie]

Tragic but interesting. I wonder how long it will be when we see a promo video of someone tossing a drone off of a tall building, and then watch it right itself?

Search YouTube for the guys who shut a Mavic down in flight then restarted it and it fully recovered before hitting the ground

 

[BudWalker]

I took a look at this flight; It's FLY028.DAT. It looks almost identical to two other incidents I looked at recently. @Cyberpower678 what is the basis for thinking that the cause was an impact on the right front and then left front motor?

The two other incidents I mentioned are
Drone crashed-- not sure what happened
Unexplained fall from the sky.

These incidents are best analyzed at a higher bandwidth than 30 Hz used by CsvView. By converting first with DatCon the max bandwidth can be seen. All three incidents started with an abrupt high freq gyro noise. From this incident


And from the second of the other two incidents


Note, the brief period no gyro noise in both incidents.

At first I thought these weren't motor/prop incidents. Certainly not like a P3 motor/prop incident as there is no well defined spinning. And, the data doesn't make it obvious that one motor/prop is the cause. I entertained the idea that the cause was a gyro sensor failure and the motor behavior is the Flight Controller's response. But, that dog didn't hunt.

In the current incident in the brief periods of no noise the leftFront and rightBack motorSpeeds going to 0.
EDIT: The following graph is the wrong one and I can't seem to replace it with the right one. You'll have to believe me. See post #72 below


The safe answer here is that I don't actually know what causes this. But, since all three incidents are almost identical I suspect there is some common failure. I.e., it's the Mavic, not the pilot.

My current favorite theory is that the blade attach rivet has started to fail and the blade is vibrating about it's axis. This is the cause of the gyro noise.

What was the condition of the props after recovery?

Good luck.

 

[Cyberpower678]

I took a look at this flight; It's FLY028.DAT. It looks almost identical to two other incidents I looked at recently. @Cyberpower678 what is the basis for thinking that the cause was an impact on the right front and then left front motor?

The two other incidents I mentioned are
Drone crashed-- not sure what happened
Unexplained fall from the sky.

These incidents are best analyzed at a higher bandwidth than 30 Hz used by CsvView. By converting first with DatCon the max bandwidth can be seen. All three incidents started with an abrupt high freq gyro noise. From this incident
View attachment 15563

And from the second of the other two incidents
View attachment 15564

Note, the brief period no gyro noise in both incidents.

At first I thought these weren't motor/prop incidents. Certainly not like a P3 motor/prop incident as there is no well defined spinning. And, the data doesn't make it obvious that one motor/prop is the cause. I entertained the idea that the cause was a gyro sensor failure and the motor behavior is the Flight Controller's response. But, that dog didn't hunt.

In the current incident in the brief periods of no noise the leftFront and rightBack motorSpeeds going to 0.
View attachment 15567

The safe answer here is that I don't actually know what causes this. But, since all three incidents are almost identical I suspect there is some common failure. I.e., it's the Mavic, not the pilot.

My current favorite theory is that the blade attach rivet has started to fail and the blade is vibrating about it's axis. This is the cause of the gyro noise.

What was the condition of the props after recovery?

Good luck.

Thank you BudWalker. I forgot that the sampling rate is low on CSVview. I wish that can be adjusted in the software itself. What is the sampling rate you recommend in these situations?

 

[BudWalker]

Thank you BudWalker. I forgot that the sampling rate is low on CSVview. I wish that can be adjusted in the software itself. What is the sampling rate you recommend in these situations?

The highest possible. In DatCon it looks like

The reason that this isn't a CsvView option is that CsvView is a front end to other converters besides DatCon. I've tried to keep CsvView log type neutral and changing the sampling rate only applies to .DAT files. I had always assumed that this wouldn't be required very often and CsvView could be kept clean. Maybe it's time to change that assumption and add .DAT specific features to CsvView. It's gonna feel dirty though.

 

[MavicCF]

I took a look at this flight; It's FLY028.DAT. It looks almost identical to two other incidents I looked at recently. @Cyberpower678 what is the basis for thinking that the cause was an impact on the right front and then left front motor?

The two other incidents I mentioned are
Drone crashed-- not sure what happened
Unexplained fall from the sky.

These incidents are best analyzed at a higher bandwidth than 30 Hz used by CsvView. By converting first with DatCon the max bandwidth can be seen. All three incidents started with an abrupt high freq gyro noise. From this incident
View attachment 15563

And from the second of the other two incidents
View attachment 15564

Note, the brief period no gyro noise in both incidents.

At first I thought these weren't motor/prop incidents. Certainly not like a P3 motor/prop incident as there is no well defined spinning. And, the data doesn't make it obvious that one motor/prop is the cause. I entertained the idea that the cause was a gyro sensor failure and the motor behavior is the Flight Controller's response. But, that dog didn't hunt.

In the current incident in the brief periods of no noise the leftFront and rightBack motorSpeeds going to 0.
EDIT: The following graph is the wrong one and I can't seem to replace it with the right one. You'll have to believe me.
View attachment 15567

The safe answer here is that I don't actually know what causes this. But, since all three incidents are almost identical I suspect there is some common failure. I.e., it's the Mavic, not the pilot.

My current favorite theory is that the blade attach rivet has started to fail and the blade is vibrating about it's axis. This is the cause of the gyro noise.

What was the condition of the props after recovery?

Good luck.

Thank you BudWalker! The condition of the props does fit you ur theory. The front left and back right was both missing one blade at the rivet. Which is weird as they were brand new with only a few flights on them. Thanks again to both you and Cyberpower678! I love this forum, so many smart people!-CF

 

[BudWalker]

Since I can't seem to replace that third graph in post #68 here it is

 

[MavicCF]

Do you think DJI is likely to cover this one?

 

[BudWalker]

Do you think DJI is likely to cover this one?

They should IMHO. But, it depends on which DJI person analyzes your flight. Generally, they are pretty good. But, not always as in the second incident I referred to
Drone crashed-- not sure what happened
You should contact @Arizona Al to see what his approach to DJI is.

Good luck.

 

[Piers]

Hi all! Hoping to get some help from you guys about todays crash. I was out for a typical routine flight above a friends house. I had been cruising around for a while and decided to flip into sport mode. As soon as I pitched forward in sport mode, it flipped (I think) over the front left corner and proceeded in a succession of summersaults to the ground. The results aren't pretty. The gimbal/camera are almost completely ripped off, the front right landing gear/antenna is broken, and the top of the body is popped up. I'm guessing either a prop or a motor failure although it could have been one of the small birds in the area. I was hoping I could get someone to analyze my flight records for me and tell me if it was my fault or if DJI is likely to eat this one. First though, I need to know how to upload theses records to this sight. Thanks in advance! -CF

I think maybe the propellor was not connected properly!

 

[MavicCF]

Hay Piers! We found the solution thanks to Cyberpower678 and Budwalker. The props were on ok but the front left/back right each lost a blade (half the prop) when the rivets that held them in failed. Thanks for your input! -CF