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Vibration while flying down after a crash - Need help to diagnose
205 12 4-29 11:30
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Pierrick35
lvl.1
Flight distance : 101969 ft
France
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Hi,

after a crash that I thought had damaged the camera, my FPV was flying ok. However, after a couple of days, it started vibrating weirdly, especially when I fly downwards.

I have a video that shows it. See how it vibrates at 0:09 and 0:12:
This happens suddenly and can cause the FPV to move to the right or the left or simply spin without any warning.

I would like to repair it but I am not sure which parts are causing the vibration. I have attached 2 pictures of the damages of the crash:
  • Junction in right rear arm. However, this was the result of a previous crash and it never affected my flights afterwards. Or maybe it's getting worse?
  • Camera. I had to push it back to put it back into place. Maybe there is a problem and I should open my FPV? I am just not sure this could affect my flights

Could you help me find out what needs to be done to fix it? Or should I just send it back to repair it?

Thanks!
Pierrick


arm.jpg

Camera

Camera
4-29 11:30
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Duane Degn
First Officer
Flight distance : 425755 ft
United States
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It looks like the right rear arm is broken.
"Or maybe it's getting worse?" This would be my guess.  

Personally, I'd try to use some sort of epoxy with fiberglass or carbon fiber tape to fix it. You could also purchase a replacement arm to fix it. Sending it to DJI would likely result in the best quality fix but I think it would also be the most expensive option.

There's a place in the UK which sells parts. Here's a link to the right rear arm they sell. You can also find people selling parts on ebay and aliexpress.
It's possible you also damaged the internal frame but hopefully fixing the arm will be enough.

4-29 11:44
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tomekyo
Second Officer
Flight distance : 3032835 ft
Netherlands
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you should definitely do something about it if you don't want to smoke up your motors. The vibrations caused by the damage induce so called D-term oscillations, which make eventually your motors very hot up to the point of burning them out. In any case making the quad rigid shoudl do the trick ...
4-29 11:52
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Buster1
lvl.4
Flight distance : 677028 ft
United States
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My non-crashed FPV has some vibrations similar to yours when descending rapidly. Prop wash maybe? There  are many owners that have reported it.

But I’d definitely fix that rear arm, get new props on bro! Oh... and remove the arm stickers!  
4-29 15:43
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Duane Degn
First Officer
Flight distance : 425755 ft
United States
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Buster1 Posted at 4-29 15:43
My non-crashed FPV has some vibrations similar to yours when descending rapidly. Prop wash maybe? There  are many owners that have reported it.

But I’d definitely fix that rear arm, get new props on bro! Oh... and remove the arm stickers!  [view_image]

"My non-crashed FPV has some vibrations similar to yours when descending rapidly. Prop wash maybe?"

Yes, descending through the prop wash isn't smooth even on a drone in good condition.

"and remove the arm stickers!"
That's crazy talk. How will the propellers know which way to turn without the stickers?
4-29 15:58
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youngleeyu
lvl.2
Flight distance : 446690 ft
United States
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I think tomekyo might got it right. You need definitely fix the arm and make it as rigid as before. From your video, I can actually hear the motors noise in sync with the video vibration. The PID feedback of the drone is not fit for flying if the frame's rigidity is altered.

And as others mentioned, a new set of props is a must, at least when you troubleshoot this issue.
4-29 18:59
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DJI Stephen
Super Moderator

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Hello there Pierrick35. I am sorry for the trouble this has caused and thank you for reaching out.  Since there was a crash that happened before on your DJI FPV before and now you are having this issue on the said DJI drone. It would be best to contact our DJI support team at https://www.dji.com/support for further assistance. We have a team that will do there best to check the said DJI drone and give out the best resolution for this issue. Again I am sorry for this trouble and thank you.
4-29 19:51
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Pierrick35
lvl.1
Flight distance : 101969 ft
France
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Thanks for all the replies! Much appreciated. I will get in touch with DJI support and then probably buy new props and a back right arm.
4-29 22:38
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Depp
Captain
Flight distance : 1140292 ft
Germany
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To me it doesn't look like the arm but rather to top plate holding the arm. Definitely replace it.
4-30 03:17
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Buzzyone
Captain
Flight distance : 2417297 ft
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United Kingdom
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Pierrick35 Posted at 4-29 22:38
Thanks for all the replies! Much appreciated. I will get in touch with DJI support and then probably buy new props and a back right arm.

Buy the middle frame too, the screw that is pulled away from the heatsink cover goes through the frame and into the top of the rear arm, if its pulled out then the stub will be split from the rear of the frame.

4-30 13:03
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Pierrick35
lvl.1
Flight distance : 101969 ft
France
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Thanks again to all for the help. My FPV just came back from the service center in the Netherlands and it flies perfectly now!
5-15 11:29
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FlyingSnoopy
lvl.3

Greece
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Pierrick35 Posted at 5-15 11:29
Thanks again to all for the help. My FPV just came back from the service center in the Netherlands and it flies perfectly now!

How much did it cost for this kind of service? Do you know which parts were replaced?
5-15 23:39
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Pierrick35
lvl.1
Flight distance : 101969 ft
France
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FlyingSnoopy Posted at 5-15 23:39
How much did it cost for this kind of service? Do you know which parts were replaced?

150 €

They replaced both parts around the area that was broken (arm and body shells).
One bad thing: they resetted the firmware so I had to re-set all my settings.
5-16 02:00
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