Fell out the sky. Flight record help.

SamRaju · Apr 27, 2018

Hi guys,

So I'm new to flying drones. I bought myself a Mavic Air and have been flying it for a week now. Yesterday I was at the park showing it off to the girlfriend as you do. I was only at about 5ft in sports mode going about 22mph and it cut out. Not too sure why.

I have downloaded the flight record but when I go to view it it opens up on note pad and its a bunch of weird letters and numbers. I wanted to post it up on here to see if anyone could work out why my drone decided to crash.

Regards,

Sam.

msinger · Apr 27, 2018

SamRaju said:
I have downloaded the flight record but when I go to view it it opens up on note pad and its a bunch of weird letters and numbers.

Upload the TXT file here.

SamRaju · Apr 27, 2018

msinger said:
Upload the TXT file here.

Wow that gives you a lot of information!! What would I need to upload for people to see? The whole flight? It only lasted a few seconds but there's a lot there!

Simmo · Apr 27, 2018

Just follow the instructions in the link that msinger gave you. Upload the TXT file and then post the link back here.

SamRaju · Apr 27, 2018

Not to sure if this will help but I have attached the flight record file. Can someone please take a look. If you have a look at the height it says it rapidly climb to.....doesn't make sense to me as I know for a fact it didn't go any higher than the 5ft it was originally at.

Thank you

Sam

SamRaju · Apr 27, 2018

Simmo said:
Just follow the instructions in the link that msinger gave you. Upload the TXT file and then post the link back here.

Ah sorry didn't realise I could post the link.

DJI Flight Log Viewer - PhantomHelp.com

Simmo · Apr 27, 2018

Did you hit those goal posts???

SamRaju · Apr 27, 2018

Simmo said:
Did you hit those goal posts???

Nope that satellite image is old. They’re no longer there. It didn’t hit anything at all. I thought it might have had something to do with travelling at speed and when I let go of the right stick (don’t know the technical name for it) the wind caused the drone to flip. I also don’t understand why it went to 32ft as well. No way it climbed at all. I’ve even watched the video footage. Doesn’t climb or hit anything.

SamRaju · Apr 27, 2018

The only other thing I could think of was how these drones cut out if you turn them around right? I’m sure I’ve seen people hold them and flip them to switch them off. Could it be possible that as I pulled the right stick back when traveling at 20something mph it causes the front end of the drone to lift really high and sort of flip and cut the power? Maybe this is why you see the vertical speed increase? The front end went higher which caused it to climb a little before it dropped back down to the ground.

sar104 · Apr 27, 2018

SamRaju said:
The only other thing I could think of was how these drones cut out if you turn them around right? I’m sure I’ve seen people hold them and flip them to switch them off. Could it be possible that as I pulled the right stick back when traveling at 20something mph it causes the front end of the drone to lift really high and sort of flip and cut the power? Maybe this is why you see the vertical speed increase? The front end went higher which caused it to climb a little before it dropped back down to the ground.

This likely requires one of the DAT files to figure out what happened. The txt log data agree broadly with your description, but there is no indication of what actually happened. The drop appears to have occurred before either the pitch or roll exceeded the cutoff levels. Did the motors actually stop?

swooshdave · Apr 27, 2018

Sport mode, 5ft off the ground, showing off... had it a week.

Hopefully it wasn't too damaged.

RayOZ · Apr 27, 2018

Warning about motor obstructed just before it flipped. Did hit a bird or something? Check the motors and props, maybe there’s a trace it hit something.

sar104 · Apr 27, 2018

RayOZ said:
Warning about motor obstructed just before it flipped. Did hit a bird or something? Check the motors and props, maybe there’s a trace it hit something.

The motor obstructed message was at 297 s, so probably after it hit the ground.

swooshdave · Apr 27, 2018

sar104 said:
The motor obstructed message was at 297 s, so probably after it hit the ground.

The ground would definitely obstruct a motor.

swooshdave · Apr 27, 2018

Will you share the video?

laurens23 · Apr 28, 2018

SamRaju said:
If you have a look at the height it says it rapidly climb to.....doesn't make sense to me as I know for a fact it didn't go any higher than the 5ft it was originally at.

The barometric altitude sensor is slow and inaccurate, you can see it gradually going down when the drone already crashed. If you check the sWaveHeight, the measurement from the ultrasonic sensor, you see that you were between 1.5 and 3.2 meter. the 9m from the barometric sensor is wrong.

what I think happened:
But you are on to something. The barometric sensor went rapidly from a correct ~1.5m up to an incorrect 9m for seemingly no good reason. To compensate the drone would have wanted to decrease altitude. At the same time you also go from 35 deg pitch forward to 35 deg pitch back to brake. These two things at low altitude made the drone clip the ground (sWaveHeight =0) after that it tumbled around the roll axis.
Normally the sWaveHeight should prevent the drone from actually hitting the ground. but with the large pitch angle change and low altitude it might have been a case of too little too late to avoid hitting the ground.

my speculation for the rout cause:
Maybe going from 35 deg forward to 35 deg backward caused some pressure differential (lower pressure) in the drone giving false readings to the barometric pressure sensor.

Someone can test it by, at a higher altitude, flying 35 deg pitch forward then 35 deg pitch backward then look at the height readings.

swooshdave · Apr 28, 2018

I doubt the drone relies only on barometric pressure to determine altitude. As you said it doesn’t react quickly enough to give an accurate rough indication of actual height.

Wouldn’t it also rely on the gyros and accelerometer to know it was rising to 9m?

It sounds like the video and DAT are still needed.

sar104 · Apr 28, 2018

swooshdave said:
I doubt the drone relies only on barometric pressure to determine altitude. As you said it doesn’t react quickly enough to give an accurate rough indication of actual height.

Wouldn’t it also rely on the gyros and accelerometer to know it was rising to 9m?

It sounds like the video and DAT are still needed.

The rate gyros don't provide any information about linear motion, but the accelerometers do, and are the highest sample-rate data source.

SamRaju · Apr 28, 2018

swooshdave said:
Sport mode, 5ft off the ground, showing off... had it a week.

Hopefully it wasn't too damaged.

Lol yeah stupid idea I know.

No damage at all. Still seems to be flying perfectly fine.

SamRaju · Apr 28, 2018

swooshdave said:
I doubt the drone relies only on barometric pressure to determine altitude. As you said it doesn’t react quickly enough to give an accurate rough indication of actual height.

Wouldn’t it also rely on the gyros and accelerometer to know it was rising to 9m?

It sounds like the video and DAT are still needed.

Is there an easy way of getting the video up or would I need to upload to YouTube and share the link? Also how do I go about getting the DAT. I have no idea what that is.