Drone in the air thinks I'm close to the ground

[stickerey]

Hey guys,

Today I took out my Air 2 but it acted very weird. When up in the air at like 20-30m I held down the stick for descending but it didn't do anything, then it switched to auto-landing. This behaviour usually happens when I'm close to the ground like 0.5m then it would go any lower but it switches to auto landing instead, which is fine, because yeah, I'm close to the ground. But why would the drone behave like such in so high up in the sky?

It has never done it before and I'm a bit nervous about it.

 

[new2mavic]

Probably because the IR sensor at the bottom detected something in the air close to it making the FC believe that the craft was close to the ground. There is a recent report on the same issue although the craft was an M2 : Drone Going into Landing Mode

 

[stickerey]

Can it be that the sensors don't work at all on my Mavic Air 2? I have the forward and backward sensors icon red in the app.
Nevermind, it was just that the assistant was turned off. So there was nothing under the drone for sure, and it did every single time I took off.

 

[new2mavic]

The bottom IR sensor of the Air 2 cannot be turned off in the setting. If it was off due to other reasons the craft wouldn't have paused descending. It would have just keep going down until the throttle stick is released or it hit the ground ( hard )

If the forward and backward sensor icon turned red in the app, it means they were off. Either they are turned off in the setting or the craft was in sport mode.

 

[new2mavic]

..... there was nothing under the drone for sure, and it did every single time I took off.

Then the IR sensor must be faulty. If you can post the flight log files by following this thread , it can be confirmed.

 

[stickerey]

Then the IR sensor must be faulty. If you can post the flight log files by following this thread , it can be confirmed.

Not sure if that's okay, but I have the dat file here: EXPORT_FILE_2020-10-11_19-39-19.DAT

Is there a way to determine the cause from this log?

 

[new2mavic]

It seems that this is the log file in the craft. It contains very detailed information but unfortunately only DJI can decipher the content. What's needed is the flight log file in the phone. You can find it by following this thread : Mavic Flight Log Retrieval and Analysis Guide

 

[stickerey]

It seems that this is the log file in the craft. It contains very detailed information but unfortunately only DJI can decipher the content. What's needed is the flight log file in the phone. You can find it by following this thread : Mavic Flight Log Retrieval and Analysis Guide

Ah got it. Here are the txt files from the phone (I tried opening them btw but the info looks encoded)

 

[new2mavic]

The flight data has confirmed what I suspected early. The IR height sensor is faulty consistently. This is one of the flights. Forced landing has occurred three times at heights of 20, 17 and 12 meters



It can be seen from the chart below that the height measured by the IR sensor ( solid red line ) roughly followed that reported by the barometer ( blue line ) at the beginning but once the craft went above 9m, the IR sensor reading dropped to 0.5 m and it stayed at that value basically throughout the remaining part of the flight. If the IR sensor was working normally, The output should follow that of the barometer until the craft went beyond the sensor's detection range of 11 m as indicated by the dotted red line.

 

[stickerey]

The flight data has confirmed what I suspected early. The IR height sensor is faulty consistently. This is one of the flights. Forced landing has occurred three times at heights of 20, 17 and 12 meters

Wow, it is pretty awesome that you could read all this info from the logs, thank you very much for your time! Unforuntely tho, I think I'm not sure, what the next step would be to avoid this kind of behaviour and to "fix" the IR sensor. Could you help me with this?

 

[new2mavic]

The IR sensor at the bottom consists of a IR light transmitter and a receiver. The transmitter shoots a beam of IR light to the ground / obstacle beneath the craft and the reflected light goes back to the receiver. The time of flight of the beam tells the distance. It appears to me that there is a shortcut for the IR light from the transmitter to go to the receiver. Can dirts on the sensor cause that ? I am not sure. I would suggest cleaning it and try again. If the problem persists, sending it back to DJI is the only way to go. It should still be under warranty.

 

[stickerey]

The IR sensor at the bottom consists of a IR light transmitter and a receiver. The transmitter shoots a beam of IR light to the ground / obstacle beneath the craft and the reflected light goes back to the receiver. The time of flight of the beam tells the distance. It appears to me that there is a shortcut for the IR light from the transmitter to go to the receiver. Can dirts on the sensor cause that ? I am not sure. I would suggest cleaning it and try again. If the problem persists, sending it back to DJI is the only way to go. It should still be under warranty.

Oh wow, then I know what could have happened. It was a huge fog in the forest I was in. and in the air it was denser than close to the ground. Can it be that the IR sensor thought that the dense fog is actually ground ?

 

[new2mavic]

Oh wow, then I know what could have happened. It was a huge fog in the forest I was in. and in the air it was denser than close to the ground. Can it be that the IR sensor thought that the dense fog is actually ground ?

That's very likely to be the cause.

 

[InvisibleName]

Oh wow, then I know what could have happened. It was a huge fog in the forest I was in. and in the air it was denser than close to the ground. Can it be that the IR sensor thought that the dense fog is actually ground ?

I think you've just nailed it!

 

[MA2 317]

Oh wow, then I know what could have happened. It was a huge fog in the forest I was in. and in the air it was denser than close to the ground. Can it be that the IR sensor thought that the dense fog is actually ground ?

YES.

I have read stories of the aircraft slowly rising because of the fog and taking a while to land because of it.

Just keep holding that left stick down until you land.