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Weird thing happened with my Mavic 3

bkushner

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I was planning on shooting 3 ships in port. I took off and went into speed mode to fly out to the first ship I wanted to photograph. Around 30 seconds the drone made a sharp right hand turn and started heading for one of the ships. I pulled the stick back to try and back away from the ship but it was moving on it's own headed right for it. I quickly moved the switch out of SPEED Mode in hopes the sensors would kick in and avoid a collision. This got control back and I carried on the flight without any other issues. This has happened before. Anyone know what might be happening? Here is my log.

 
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I can't help you but I can feel your relief when you got it back under control.
 
Just out of curiosity what were the winds like?
I ask because from 3:44 to around 4:08 the drone is flying near full speed in sports mode with seemingly very little nose down pitch.
 
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...Anyone know what might be happening?
Yeah... the primary isn't that the drone seems to continue horizontal flight uncommanded, the drift is instead in the yaw axis... it's like the IMU suddenly lose it's sense about which direction it points & by that don't apply braking as it should to stop the horizontal movement when you release the sticks.

Looked at this section of the flight path (along the yellow hand drawn line)...

1679145168086.png

It's very apparent that we have an uncommanded yaw rotation when it starts to turn towards the ship, the drone even continue to turn in the opposite direction to what you command.

Comparing the IMU & GPS velocities clearly show big deviations ongoing during the incident... & your flight mode change doesn't stop it, instead it looks to be that your drone get away from the ship.

The red is the velocity deviation North
The green is the velocity deviation East
The thin blue dashed is your rudder commands
The thin black is the yaw axis
Pink background is Sport
Blue background is Normal mode

The IMU & GPS velocity deviations should normally be very close to 0mph, here we see deviation growing up to nearly 22mph in Northerly direction & a bit later up to 15mph in easterly direction. The incident calms down (& the velocity deviations) when the drone ends up right above the ship at 43sec into the flight... the velocities gets then somewhat erratic when your drone leaves the ship & then all returns to normal.

1679145627041.png

Without a proper .DAT log we don't have access to all needed data to determine the exact changes in mag field strengths & how the compass were affected during the incident... but my belief is that something severely disturbed the compass just there close to the ship, that made it act up in a similar way as during a yaw error incident where the drone have been power up in a magnetic disturbed spot.
 
Have you checked the KP index before flight? Perhaps a disturbance of the GPS positioning due to solar wind?
Kp Index has no effect on drone flying.
By the time it's high enough to, your drone will be the last of your worries.
 
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If it was high enough, what would be happening?
-Longer time to acquire a GPS fix
-GPS positions (like the HP) may not be as precise
-You lose GPS fix & find your drone in ATTI mode.

All this is with a very big "may possibly happen" & then only up on the absolutely highest KP indexes (7-9), levels that high are also very rare... have never ever seen any signs coming from a high KP index in all hundreds of incidents I've looked into.
 
-Longer time to acquire a GPS fix
-GPS positions (like the HP) may not be as precise
-You lose GPS fix & find your drone in ATTI mode.

All this is with a very big "may possibly happen" & then only up on the absolutely highest KP indexes (7-9), levels that high are also very rare... have never ever seen any signs coming from a high KP index in all hundreds of incidents I've looked into.
Ok, thanks for that information.
 
Just out of curiosity what were the winds like?
I ask because from 3:44 to around 4:08 the drone is flying near full speed in sports mode with seemingly very little nose down pitch.
Yeah... the primary isn't that the drone seems to continue horizontal flight uncommanded, the drift is instead in the yaw axis... it's like the IMU suddenly lose it's sense about which direction it points & by that don't apply braking as it should to stop the horizontal movement when you release the sticks.

Looked at this section of the flight path (along the yellow hand drawn line)...

View attachment 161715

It's very apparent that we have an uncommanded yaw rotation when it starts to turn towards the ship, the drone even continue to turn in the opposite direction to what you command.

Comparing the IMU & GPS velocities clearly show big deviations ongoing during the incident... & your flight mode change doesn't stop it, instead it looks to be that your drone get away from the ship.

The red is the velocity deviation North
The green is the velocity deviation East
The thin blue dashed is your rudder commands
The thin black is the yaw axis
Pink background is Sport
Blue background is Normal mode

The IMU & GPS velocity deviations should normally be very close to 0mph, here we see deviation growing up to nearly 22mph in Northerly direction & a bit later up to 15mph in easterly direction. The incident calms down (& the velocity deviations) when the drone ends up right above the ship at 43sec into the flight... the velocities gets then somewhat erratic when your drone leaves the ship & then all returns to normal.

View attachment 161716

Without a proper .DAT log we don't have access to all needed data to determine the exact changes in mag field strengths & how the compass were affected during the incident... but my belief is that something severely disturbed the compass just there close to the ship, that made it act up in a similar way as during a yaw error incident where the drone have been power up in a magnetic disturbed spot.
Thanks for this detailed response. I think next time I will fly out much further before making my turn :) I did return to the exact ship getting close for pictures with no issues. Also as I mentioned I've had this happen in a different location in open space but again over water. I' fly 95% of the time over water...
 
...I've had this happen in a different location in open space but again over water.
As we don't have access to a readable .DAT log from M3's it's very little data to look at... meaning that we only have one value for the yaw axis for instance, that means that we lack the possibility to compare different yaw measurements from several sensors & say which one that brought in a likely wrong value in the Flight controller computation.

In a .DAT log we have yaw values from the different IMU's (if several), from the VIO yaw (if height is low enough, it's a kind of visual compass using the VPS sensor logging rotation), the gyro rotation & the compass rotation. With all these logging the same but through different sources it's usually possible to determine which one is wrong. And sometimes the FC chose to go with the one that is wrong... & then yaw error like conditions usually occurs.

Have seen VIO induced yaw errors before... but they are very rare & usually occurs like 20-ish feet or closer over water, & the yaw error incident goes away when ascending up outside the VPS sensor operational distance. But in your incident the drone was up on 80-ish feet so the VIO yaw wouldn't have worked.

But if this happens again, over water with a distinct pattern (waves)... try to ascend & see if that restores the flight behavior.
 
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IMU calibration is my first response to any weird or uncommanded drone movements. Might want to invest in a Rescue Jacket for your water flights, reduces the pucker factor. I use one on my Air2 as most of my flights are over water. Of course you still have to have a way to retrieve it, just in case. Have fun.
 
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