Help: Drowned Mavic Pro

[cojobt]

Hi,

Could anyone help interpret my flight log etc for my Mavic Pro's last airborne moments, before it decided to roll over and swim with the fishes?

I was flying low to the surface of a lake, then began to lift, when the controller beeped with the warning 'Drone has rolled over', and I looked out just in time to see it do a backflip and go straight under the water.

I hope these are the right files.

Thanks in advance, if anybody has the time!

 

[brett8883]

Hi,

Could anyone help interpret my flight log etc for my Mavic Pro's last airborne moments, before it decided to roll over and swim with the fishes?

I was flying low to the surface of a lake, then began to lift, when the controller beeped with the warning 'Drone has rolled over', and I looked out just in time to see it do a backflip and go straight under the water.

I hope these are the right files.

Thanks in advance, if anybody has the time!

Unfortunately it looks like you got too close the water and got wet.
The blue line at the bottom is the height as measured by the ultrasonic sensor. You had been lowering it closer and closer with the left stick till this point until it got to 2 feet (.6 meters) above the water and then you floored the right stick forward suddenly. This caused the aircraft to pitch forward suddenly and you were on your own at that point because the aircraft is pitched forward so far it cant accurately read the height anymore. You must have realized how close you were because you suddenly release the right stick while flooring the left stick up but it was too late. The props may have even skimmed a wave or something causing them to stop since you were pitched so far.

 

[naiku]

Never fails to amaze me the amount of information you guys are able to extract from the logs.

 

[Trollistika]

Logs are easy to read. A monkey can do it, just sit down and learn to read it once and it becomes second nature. Good skill to have to analyze crashes. I wish it would have more info like exact coordinates on the hardest impact. Or maybe even a selfie shot of the operator when it crashed. Hehe. Last one is a joke.

 

[cojobt]

Unfortunately it looks like you got too close the water and got wet. View attachment 69819
The blue line at the bottom is the height as measured by the ultrasonic sensor. You had been lowering it closer and closer with the left stick till this point until it got to 2 feet (.6 meters) above the water and then you floored the right stick forward suddenly. This caused the aircraft to pitch forward suddenly and you were on your own at that point because the aircraft is pitched forward so far it cant accurately read the height anymore. You must have realized how close you were because you suddenly release the right stick while flooring the left stick up but it was too late. The props may have even skimmed a wave or something causing them to stop since you were pitched so far.

Thanks for taking the time to reply.

I lowered the drone to 2 ft off above a concrete jetty first, then pushed the right stick forward fully sending it out over the lake at full speed. The surface of the lake was approx. half a foot below the starting point, which means the drone was flying at around 2.5 ft over the surface of the water, and the lake water was vary calm, so no waves.

After about 15 metres, I began to push the left up, and that's when I got the 'drone rolled over' alert, and must have let the sticks go. The drone literally did a back flip, with the front rotors rearing up and over the back rotors, so that the drone slid down on a vertical axis into the lake water.

I've added a video of its last flight/first swim on Vimeo, in case anyone is interested:

 

[Trollistika]

Yep. A gremlin. It will he hard to diagnose this one. All so sudden! Did you recover it?

 

[cojobt]

Yep. A gremlin. It will he hard to diagnose this one. All so sudden! Did you recover it?

No, I'm afraid not. I ran back to my car, changed in to a pair of shorts, jumped into the very very cold lake, swam out a few metres, tested the depth, realised it got very deep very quickly, and swam back in again.

I've contacted a scuba diver who may be able to retrieve it but advises that the lake is very deep, so it might be difficult to find...and as 5 days have passed the chances are getting slimmer and slimmer as it may be concealed, and definitely beyond repair. It's a freshwater lake though...but dirt, plant life and the Dobhar-Chú (a legendary dog-otter hybrid monster that roams the depths) have probably made it impossible to fix.

 

[Trollistika]

No, I'm afraid not. I ran back to my car, changed in to a pair of shorts, jumped into the very very cold lake, swam out a few metres, tested the depth, realised it got very deep very quickly, and swam back in again.

I've contacted a scuba diver who may be able to retrieve it but advises that the lake is very deep, so it might be difficult to find...and as 5 days have passed the chances are getting slimmer and slimmer as it may be concealed, and definitely beyond repair. It's a freshwater lake though...but dirt, plant life and the Dobhar-Chú (a legendary dog-otter hybrid monster that roams the depths) have probably made it impossible to fix.

Ahh man! That sucks my dude! That's part of drones sadly. I've been advice by other that flying fast and low near a water body is not a good idea. I plan on never doing that seeing that it has made drones crash like yours. I suspect one of the sensors gave out a wrong output due to the physical nature of liquid. Hopefully you recover from this.

 

[STUFF2C]

Hey are there any YouTube videos that show you how to read these logs?

 

[Trollistika]

Hey are there any YouTube videos that show you how to read these logs?

I started with this link... I'm still a noob and learning but getting better every day.

Reading the Flight Log...What Does It All Mean?

I have been reading several threads that request folks to download their Flight Logs and then provide a link to the report so they can analyze whatever problem the operator had. This is a very useful capability and interesting as well. However, to a noob such as myself there are several...

forum.dji.com

 

[cojobt]

Ahh man! That sucks my dude! That's part of drones sadly. I've been advice by other that flying fast and low near a water body is not a good idea. I plan on never doing that seeing that it has made drones crash like yours. I suspect one of the sensors gave out a wrong output due to the physical nature of liquid. Hopefully you recover from this.

And just found out my household insurance doesn't cover drones, even though I have Miscellaneous Personal Items cover, so my phone, cameras, laptop, and even music production gear are covered, but not drones, even though my drone lives beside my camera in the boot of the car most of the time, and is considered equally valid as 'personal effects' to my mind. Drones are obviously too high-risk and aren't covered at all.

 

[Trollistika]

And just found out my household insurance doesn't cover drones, even though I have Miscellaneous Personal Items cover, so my phone, cameras, laptop, and even music production gear are covered, but not drones, even though my drone lives beside my camera in the boot of the car most of the time, and is considered equally valid as 'personal effects' to my mind. Drones are obviously too high-risk and aren't covered at all.

Yep. You can't fly a DSLR into a volcano, a drone you can. Too high risk. Maybe that care thing from dji might be worth it. But don't know the rules with them. Don't know if it does water damage or lost altogether. Next step is probably saving a little to get another.

 

[SpinRush]

I have to ask, and you can be honest with me, is this my destiny? As a new drone owner, am I going to crash my drone into a lake or ocean? Do they always flip or spiral out of control? I bought a Mavic Air. It’s my very first drone. How often do these things fly away even with GPS and RTH properly set?

 

[Trollistika]

I have to ask, and you can be honest with me, is this my destiny? As a new drone owner, am I going to crash my drone into a lake or ocean? Do they always flip or spiral out of control? I bought a Mavic Air. It’s my very first drone. How often do these things fly away even with GPS and RTH properly set?

Only YOU know your destiny, grasshopper. Grab it by the wooble goobles and ride it onwards!

Sadly, it's not uncommon. These random fly away\crashes do happen. Don't give up though it's part of the journey!

 

[Montana John]

I have to ask, and you can be honest with me, is this my destiny? As a new drone owner, am I going to crash my drone into a lake or ocean? Do they always flip or spiral out of control? I bought a Mavic Air. It’s my very first drone. How often do these things fly away even with GPS and RTH properly set?

If you don't fly over water at high speed and low altitude, this won't happen to you. Assuming you don't get stupid with battery power levels and come ashore when the wind warning shows up on your screen.

 

[naiku]

Logs are easy to read. A monkey can do it, just sit down and learn to read it once and it becomes second nature. Good skill to have to analyze crashes.

Oh I have no doubt if I were to sit down and spend a little time analyzing a flight log I could read them (hell, my job is spending all day long looking at data). But, it does not take away from how great it is that other members are able to read the log within a couple hours of it being posted, then break it down as such that anyone reading can understand exactly what happened to the drone. It's also really helpful that along with the written explanation, the graph is posted so someone reading can start to correlate the two and understand what they are looking at.

 

[Trollistika]

Oh I have no doubt if I were to sit down and spend a little time analyzing a flight log I could read them (****, my job is spending all day long looking at data). But, it does not take away from how great it is that other members are able to read the log within a couple hours of it being posted, then break it down as such that anyone reading can understand exactly what happened to the drone. It's also really helpful that along with the written explanation, the graph is posted so someone reading can start to correlate the two and understand what they are looking at.

Never doubt yourself my dude!

 

[moosedrooln]

I have to ask, and you can be honest with me, is this my destiny? As a new drone owner, am I going to crash my drone into a lake or ocean? Do they always flip or spiral out of control? I bought a Mavic Air. It’s my very first drone. How often do these things fly away even with GPS and RTH properly set?

I was so nervous the first time I flew my MP I was literally shaking. After a few flights and becoming familiar with it I gained confidence and really started enjoying it. Before long I was flying all the time and taking greater risks with close fly-by's etc... for cool footage. Thunderdrones is literally putting my MP in the mail today sending it back to me after repairing it. $300 is what my first crash cost me, but it was 100% all my fault. I hit a powerline flying too low. From what little time I've spent on this forum it appears to me that most of the disasters are the fault of the guy running the sticks, not the bird itself.

 

[BudWalker]

Hi,

Could anyone help interpret my flight log etc for my Mavic Pro's last airborne moments, before it decided to roll over and swim with the fishes?

I was flying low to the surface of a lake, then began to lift, when the controller beeped with the warning 'Drone has rolled over', and I looked out just in time to see it do a backflip and go straight under the water.

I hope these are the right files.

Thanks in advance, if anybody has the time!

The "back flip" happened because an "obstacle" (probably the water surface) was detected and the emergency brake was applied. The response was the aggressive pitch up that you saw. The pink background below shows the emergency braking.

Also, note that usonic_h was invalid indicating that it wasn't getting a return. The .txt will show a value of 0.0 when the usonic_h is invalid.

The MP had been climbing for about .8 secs when the emergency brake/pitch up occurred.


I looked at the motor data and it doesn't look like any of the props contacted the water.

 

[sar104]

The "back flip" happened because an "obstacle" (probably the water surface) was detected and the emergency brake was applied. The response was the aggressive pitch up that you saw. The pink background below shows the emergency braking.
View attachment 69872
Also, note that usonic_h was invalid indicating that it wasn't getting a return. The .txt will show a value of 0.0 when the usonic_h is invalid.

The MP had been climbing for about .8 secs when the emergency brake/pitch up occurred.
View attachment 69873

I looked at the motor data and it doesn't look like any of the props contacted the water.

That's exactly correct, with one additional factor that in my opinion may be a firmware problem:



The aircraft did not actually backflip as described by the OP, but it reached 76° pitch in braking, followed by motor shutdown:



That's confirmed in the event stream:

1156.864 : 62593 [L-FDI][CTRL]: fault on , tilt_ctrl_fail​

1156.880 : 62594 [L-FMU/MOTOR] Stop. reason:roll over or atti fail​

1156.882 : 62594 [L-FMU/MOTOR]Total start times: 1, time:1156.88​

1156.882 : 62594 [L-PWM]set actuator mode:IDLE​

1156.882 : 62594 [L-FLYMODE]CTRL reset all by motor stopped​

1156.882 : 62594 [L-RC]craft ctrl failed!!!​

1156.883 : 62594 [L-FMU/FSM]state changed. cur: motor off​

1156.884 : 62594 [L-FDI][CTRL]: fault off, tilt_ctrl_fail​

1156.899 : 62595 [L-IMU]set imu switch level = 1​

1157.062 : 62603 [L-RC]Emergency break. rc vib!​

1157.199 : 62610 [L-FDI]NS(0) GPS(0): fault on , abrupt​

Unless the parameters on this aircraft have been modified, allowing 76° of pitch during braking, the firmware should not shut down the motors in flight as a result.