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Mavic Air 2 unstable flight on return path

Korrd

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While recording a sunset, my drone suddenly became unstable, as if the gimbal had overloaded and was aiming randomly around.

A wind warning was issued, despite winds being not that strong, and the drone became jumpy when coming back for an emergency landing.

On landing, it would not stop the motors, so I had to stop it with CSC.

Logfiles attached.

Any ideas as to what could have caused it?

I noticed that despite the DJI app showing 12 sats, flight logs display between 9-11, which is weird.

I've also noticed that there are no flight logs on aircraft, but only the mobile app ones.
 

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  • DJIFlightRecord_2021-10-25_[19-21-33].txt
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eEridani

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Winds rarely feel as strong as they really are... and you nearly landed your drone in the harbor. The gimbal angles all look reasonable, too. Nothing stands out. And winds there yesterday were 18 mph - gusts probably higher - so near the drone's limits.

My guess the gimbal was overloaded on landing - the camera hitting something laying on the roof.

Capture.JPG
 
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Korrd

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It became unstable at the point marked 90% battery. That's what made me go back.


Near landing in the bay was not so for landing, but to capture this beautiful pic:
 

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Korrd

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Regarding wind, this is the wind at the general area when that flight took place. It's not that strong. I've flown on 55 km/h winds many times, with no issues at all.
 

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Phantomrain.org

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Regarding wind, this is the wind at the general area when that flight took place. It's not that strong. I've flown on 55 km/h winds many times, with no issues at all.
I can see by the picture that the wind was not that strong, So there are two issues that are strange < the drone not turning off and becoming unstable can you post any of the video that was recorded ? The transmission crashing would cause the gimbal to go crazy ,

The bigger issue is why the drone did not shut down , almost seems like the sensors got confused from the sun reflection although i have tested flying into the sun many times without issue.

Got me interested : 🤔

Phantomrain.org
Gear to fly in the Rain.
 

eEridani

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Gorgeous pic.

  • Max Wind Resistance​

  • 8.5-10.5 m/s (Level 5) ~~ 28 to 37kph
The forecast above shows 33kph - pretty is close to the drone's happy limit. Considering that's a steady wind forecast, and knowing gusts are often quite a lot higher, seems the wind warnings were appropriate.

I'm a bit dubious of flights in 55 kilometer winds - the drone's top speed is around 70 kph in sport mode.
 

Korrd

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While I do tend to record screen when flying, sometimes I forget to do so, this being one of those.

the sequence of events was as follows.


1. Engines on idle while waiting for a gps lock
2. Liftoff on homepoint set message
3. Go all the way to the docks, and hover mast high to capture that picture.
4. Go back to altitude, and fly to the point marked 90% battery.
5. At that moment. The drone shakes as if hit by something. I was looking at itand there was nothing around it.
6. I get a strong wind warning, and the gimbal begins shaking and aiming at random spots as if a huge hand were shaking it. That when I turn around and beeline for the rooftop I was at. The attitude indicator was showing the drone fully tilted forward.
7. I descend, and notice that the drone is not slowing down nor autolanding, despite it being mere centimeters from the ground, aux light turned on and all. at that point, it was next to me, shaking shaking wildly.
8. CSC command, then it goes into forced landing. Props don’t stop, yet it lands by hitting the ground with front right leg. At that point, props stop and it comes to a halt.

I’ve inspected it. No damage of any kind. I restarted it, and it hovered, then flew again without issues.

I’m intrigued as to what may have caused such chain of events.
 
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eEridani

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I can see by the picture that the wind was not that strong, So there are two issues that are strange < the drone not turning off and becoming unstable can you post any of the video that was recorded ? The transmission crashing would cause the gimbal to go crazy ,

The bigger issue is why the drone did not shut down , almost seems like the sensors got confused from the sun reflection although i have tested flying into the sun many times without issue.

Got me interested : 🤔

Phantomrain.org
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The visions sensors were offline - so it might be the drone didn't really know it had landed.

There's only this bit of info towards the last:
OSD.flightAction = Landing (Vert Low Limit)
OSD.flycState = Forced Landing
 
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Korrd

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Gorgeous pic.

  • Max Wind Resistance​

  • 8.5-10.5 m/s (Level 5) ~~ 28 to 37kph
The forecast above shows 33kph - pretty is close to the drone's happy limit. Considering that's a steady wind forecast, and knowing gusts are often quite a lot higher, seems the wind warnings were appropriate.

I'm a bit dubious of flights in 55 kilometer winds - the drone's top speed is around 70 kph in sport mode.
Agreed. Still, specs are conservative. It can handle some more than that, as in this example (see weather, inflight wind tab):



I do have more flight records on higher winds. Gotta find them among a sea of flight records though.
 

Korrd

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The visions sensors were offline - so it might be the drone didn't really know it had landed.

There's only this bit of info towards the last:
OSD.flightAction = Landing (Vert Low Limit)
OSD.flycState = Forced Landing
Weird though, as it uses an IR altimeter in order to determine that instead of vision sensors (you can see it emitting dim red light in the dark if you stand right below the drone). That’s how it can land in total darkness when aux light is set to off.
 

Korrd

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The bigger issue is why the drone did not shut down , almost seems like the sensors got confused from the sun reflection although i have tested flying into the sun many times without issue.
Weird as well. The sun was already below the horizon, and landing spot was in the dark behind buildings.

All those aforementioned factors are the reason why I posted it here. It’s really vexing. I can’t see anything that would point to the issues observed during this flight.

Curiouser and curiouser.
 
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eEridani

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The IR isn't infallible, it has a cone of sensitivity, and the fact the gimbal bumped something on the way down is probably a hint. Was the drone landing on a flat smooth surface? Or did it land on something?

The last three seconds of flight are the only part of the flight that seems sketchy - the drone reports a stuck gimbal then rolls and pitches. Sounds like it struck something coming down.
 

sar104

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While recording a sunset, my drone suddenly became unstable, as if the gimbal had overloaded and was aiming randomly around.

A wind warning was issued, despite winds being not that strong, and the drone became jumpy when coming back for an emergency landing.

On landing, it would not stop the motors, so I had to stop it with CSC.

Logfiles attached.

Any ideas as to what could have caused it?

I noticed that despite the DJI app showing 12 sats, flight logs display between 9-11, which is weird.

I've also noticed that there are no flight logs on aircraft, but only the mobile app ones.
Did you look at the wind speeds during that flight (~ 30 mph / 13 m/s)?

 

PhiliusFoggg

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A point, unless you have changed the response to the CSC postion from the default of "Emergency only" or something similar, I suspect that your "CSC" did not stop the motors and that what did stop them was the throttle being held fully closed, there is an important to understand difference between the two scenarios.

I would be somewhat surprise in the lack of vision senors had anything to do with the motors not stopping. The other night I hand caught my Mavic Mini in darkness, no VPS, the motors stopped as normal.
Did the drone move on the ground after it landed? If so that may be the problem, when hand catching the hand holding the drone must be fairly still until the motors stop otherwise the drone starts to fight the capture.

Is the GPS count in that area normally that low? 10 to 13 being the maximum I see in the Airdata data.
Where I fly I would consider 18 low-ish, I think I have seen 24 with the one of the Minis and maybe 26 with the FPV.
 
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Korrd

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The IR isn't infallible, it has a cone of sensitivity, and the fact the gimbal bumped something on the way down is probably a hint. Was the drone landing on a flat smooth surface? Or did it land on something?

The last three seconds of flight are the only part of the flight that seems sketchy - the drone reports a stuck gimbal then rolls and pitches. Sounds like it struck something coming down.
The gimbal started acting up on the 90% data point of your 3D flight path. It was in the middle of the air then.

Terrain on landing spot was flat cement. A rooftop. Nothing to bump into.
 

Korrd

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A point, unless you have changed the response to the CSC postion from the default of "Emergency only" or something similar, I suspect that your "CSC" did not stop the motors and that what did stop them was the throttle being held fully closed, there is an important to understand difference between the two scenarios.

I would be somewhat surprise in the lack of vision senors had anything to do with the motors not stopping. The other night I hand caught my Mavic Mini in darkness, no VPS, the motors stopped as normal.
Did the drone move on the ground after it landed? If so that may be the problem, when hand catching the hand holding the drone must be fairly still until the motors stop otherwise the drone starts to fight the capture.

Is the GPS count in that area normally that low? 10 to 13 being the maximum I see in the Airdata data.
Where I fly I would consider 18 low-ish, I think I have seen 24 with the one of the Minis and maybe 26 with the FPV.
I've never seen so many sats. I usually fly on 16ish or so. Most I've seen was 19.

Maybe, count is lower on the southern hemisphere, which is where I am right now.
 

Korrd

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Did you look at the wind speeds during that flight (~ 30 mph / 13 m/s)?

Yeah. As stated on earlier posts, it can fly stably on higher winds than its specs state. I've done it so myself several times without issues. There is an example above.
 

Phantomrain.org

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Weird as well. The sun was already below the horizon, and landing spot was in the dark behind buildings.

All those aforementioned factors are the reason why I posted it here. It’s really vexing. I can’t see anything that would point to the issues observed during this flight.

Curiouser and curiouser.
Im ruling out the wind, and stacking my chips on the Transmission signal failing , that would explain the loss of camera control and why the Drone could not shut off. Number of sats does not always equate to transmission signal being strong.

When we tested the Camera under water , we loose the transmission signal to the camera and it goes crazy but than finds the signal again as is fine.

On my last long distance flight i lost signal even though I had GPS signal and Sats.

Phantomrain.org
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Meta4

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While recording a sunset, my drone suddenly became unstable, as if the gimbal had overloaded and was aiming randomly around.
There is no hint of instability in your flight data at or around 90% battery.
The pitch, roll and yaw data show perfectly normal\, smooth flight.
Did you see teh drone flying in an unstable manner, or just see the camera acting up?
It's common for the gimbal to glitch in a strong side wind.
 

Korrd

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There is no hint of instability in your flight data at or around 90% battery.
The pitch, roll and yaw data show perfectly normal\, smooth flight.
Did you see teh drone flying in an unstable manner, or just see the camera acting up?
It's common for the gimbal to glitch in a strong side wind.
I saw the drone shaking with my own eyes, as I was looking at the 90% mark, and also saw the gimbal on screen do weird stuff too. Can't explain why, unfortunately.

I will conduct a test flight tomorrow and see if I can replicate its behaviour under similar conditions, as it'll be windy during the morning. I will do the same under no wind conditions later in the day, as it will be windless at about 1800, this time recording screen too.
If I can't make it fail, I'll just archive it as a fluke and leave it at that. Otherwise, we should get some more data to analyze.
 
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