Mavic Air Fly-away

[Helgegustav]

Hello!

So my Mavic Air flew away today. I started off with 76% battery, recorded RTH point with gps signal and all, and when I reached 30m altitude it freaked out. It went full speed ahead away from me. activating RTH function had no effect at all and it didnt respond to the controller. ( after some googling I've discovered that sport-mode is your friend in these situations...)

I lost videotransmission at about 250m distance ( 4km range my ***) but somehow it was still transmitting its GPS-position, which made me able to find it about 1km away from starting point.

It had crashed into a pit of sand and gravel. 3 of 4 propellers broken and sand and dust trapped in the motors and air intakes. Amazingly, not a scratch on the lens, and the gimbal seems ok. I brought it home and started to clean it up, and noticed that it sounded like a freaking maracas. This fell out from behind the gimbal after a bit of shaking. I don't dare to start it because of the sand that's trapped in the motors.

I have contacted DJI support and the reseller I bought it from, hoping that some kind of warranty will cover this. I'm hoping their support is not as bad as people say.

Thoughts?

Anyone else who has been in contact with DJI support with something like this?

 

[shaunmichaelj]

Yes, i have experienced this. First time i flew the drone it did something similar and i hit the pause button. I did post and everyone said it was likely to be a pilot error. The other day, I was testing a new battery. My fingers were not touching the Joyce Stick at all, the MA was just hovering and then it freaked out. By freakout i mean it Spun around to face north and then started to elevate from roughly 6 foot off the ground and then decided to fly into a branch.. The controller wouldn't respond and in the end I had to jump and grab it out of the air. That was not a pilot error and its not the first time its happened.

What firmware version do you have may i ask?

 

[RayOZ]

Please post flight logs.

 

[Simmo]

For anyone here to try and evaluate what happened, you would need to upload your flight logs.
DJI Flight Log Viewer

 

[Helgegustav]

How do I upload logs? It is a .dat file, this site doesnt seem to handle it

 

[Simmo]

Click on my link above mate.

 

[Helgegustav]

I had the wrong folder, downloaded FlightLogs when it shouldve been FlightRecords...


I notice now that I started with 76% battery. Not 100. My bad. Hope this doesn't affect the situation.

Log: DJI Flight Log Viewer - PhantomHelp.com

 

[Simmo]

I dont know what happened at 66 seconds battery wise?
However I think you seemed to be pretty quick getting up and away? I'm sure HP wasnt set til you were quite a way out?
The Airspeed, I dont get either.
@msinger or @sar104 are the experts in this field!

 

[Helgegustav]

A little more detailed explanation:

At first when I took off I noticed the weak GPS-signal... So I tried to hover at ~11m to gain stronger signal. Around 20s battery time. After that I went up to 30m where it got full GPS-signal, and boom it takes off. I did not move the right joystick, I only told it to go up! All the horizontal movement it did by it self. ( 81.3mph not bad huh? )

Records RTH-point and flies the exact opposite way? I can see in the log viewer on the app that I moved the joysticks to try to make it come back, and yet it still goes away....

I feel so bad that I wasnt more careful, even if I do think I was careful enough. Keeping visual contact and all.

 

[Simmo]

My amateur take on it is poor GPS reception, hence poor GPS health on take off. When that picked up at height, you were in the wind. I see no control input after that and it just drifted.
At 66-8 seconds, I dunno...crash??
I see no RTH triggered or anything...dunno...
Over to the pro's!

 

[Helgegustav]

Yeah, I saw it was drifting with the wind, but it was only 1-2 m/s of wind so I thought I had it under control. I saw the moment when the motors engaged and it bailed.



Thanks for your help my man. The users you mentioned will get a notification right?

 

[Kevjones777]

It does not look like any GPS active when you took off so RTH would not have been set. It looks like you tried to set RTH while it was in the air. Why was there no GPS coverage where you launched from. The speed readings do not make sense else you have the fastest accelerating drone in the world 0.3 secs 0 to 81.3 mph.

 

[Helgegustav]

It warned for "weak signal" not "no signal", even if the log says no signal at all. So I thought that if I gained some altitude it would be stronger. And I thought it would be no problem without GPS signal because there were very little wind and it was right above me...

I don't know why there was no GPS signal from where I started. It was right next to my house so maybe the satellite wasn't in line of sight or something.

 

[joejaxvic123]

81 MPH?! Wow. I would lean towards false information. In my limited experience, I have learned not to take off without good GPS signal. Sorry for your trouble, Helge.

 

[Kevjones777]

It warned for "weak signal" not "no signal", even if the log says no signal at all. So I thought that if I gained some altitude it would be stronger. And I thought it would be no problem without GPS signal because there were very little wind and it was right above me...

I don't know why there was no GPS signal from where I started. It was right next to my house so maybe the satellite wasn't in line of sight or something.

Ja man, look one of the experienced guys will look at this log and hopefully give you a definitive answer but it does not look right. I would really like to know what happened here as well. It helps all of us.

 

[Helgegustav]

81 MPH?! Wow. I would lean towards false information. In my limited experience, I have learned not to take off without good GPS signal. Sorry for your trouble, Helge.

Yeah thanks. I guess I learned my lesson too. Just hope it won't be an expensive one.

Ja man, look one of the experienced guys will look at this log and hopefully give you a definitive answer but it does not look right. I would really like to know what happened here as well. It helps all of us.

Yeah, I wrote to DJI too. I'll update this thread when I know what happened.

 

[Kevjones777]

Yeah thanks. I guess I learned my lesson too. Just hope it won't be an expensive one.




Yeah, I wrote to DJI too. I'll update this thread when I know what happened.

Ok I think I know why the speed is insane. If the speed is calculated from the GPS and you start off with 0 sats locked on, when the sat signal is picked up they come on in stages to fix your position. It could be that the the first sat gave your aircraft a position that was close but not accurate then when the other sats locked on it repositioned the aircraft relative to the initial position. This could create the illusion that you moved from point A to point B when in fact it was merely getting you correctly positioned accurately according to the satellites. The software then thinks you have moved say 40m in 0.3 seconds and logs this as 80 mph when in fact you were at that point standing still. You can sometimes see this happening in google maps on your tablet where your location moves on the map while it is fixing your position.

 

[Helgegustav]

Ok I think I know why the speed is insane. If the speed is calculated from the GPS and you start off with 0 sats locked on, when the sat signal is picked up they come on in stages to fix your position. It could be that the the first sat gave your aircraft a position that was close but not accurate then when the other sats locked on it repositioned the aircraft relative to the initial position. This could create the illusion that you moved from point A to point B when in fact it was merely getting you correctly positioned accurately according to the satellites. The software then thinks you have moved say 40m in 0.3 seconds and logs this as 80 mph when in fact you were at that point standing still. You can sometimes see this happening in google maps on your tablet where your location moves on the map while it is fixing your position.

That makes sense.

But it doesn't explain why it even took off from the beginning. I never made the joystick input to move it horizontally when it was above 10m.

 

[sar104]

There were two problems with this flight. Firstly, there were no useable GPS data for the first 40 seconds and so it started to drift immediately. The homepoint was not set until 49 s into the flight, 88 m NNE of the controller. Secondly, the pilot continued to climb the aircraft up to its ceiling of 30 m, at which height the wind speed was too high for positional control and the aircraft was already drifting NNE at nearly 20 m/s.



Once the FC had position data it adjusted pitch and roll to attempt to hold against the wind, but it maxed out on attitude with pitch at 21° and roll at -30°. It was unable to hold and drifted away NNE at around 16 m/s.

 

[Kevjones777]

There were two problems with this flight. Firstly, there were no useable GPS data for the first 40 seconds and so it started to drift immediately. The homepoint was not set until 49 s into the flight, 88 m NNE of the controller. Secondly, the pilot continued to climb the aircraft up to its ceiling of 30 m, at which height the wind speed was too high for positional control and the aircraft was already drifting NNE at nearly 20 m/s.

View attachment 34372

Once the FC had position data it adjusted pitch and roll to attempt to hold against the wind, but it maxed out on attitude with pitch at 21° and roll at -30°. It was unable to hold and drifted away NNE at around 16 m/s.

View attachment 34373

Thanks ... this graph makes it much more clear. So in a nutshell you are saying the wind just blew it away ? and by the time the HP was set it was no where near where it took off from ?