Crash - unstable hovering since

[Adrian_M]

Hi,

I'm new to this - only had my drone a month or so - and crashed it into a wall

When i tried to restart it one motor was clearly having an issue. the others powered up then quickly shut down because the fourth did not move. i rotated the prop manually and it was a bit sticky, me manually rotating it seemed to loosen and after this it powered up fine....

The problem is when I flew, it seemed to be unstable and wouldn't hover still. It seems to pull forward when I leave the controls untouched....

Is there a way to reset, recalibrate or inspect what might be wrong? Also, I'm leaving on holiday this Friday, is there a hightened risk it could fall out of the sky if I fly it in this condition?

Any advice much appreciated - thanks

 

[Blacksails]

How is it unstable? Twitching and wiggling all over the place? Or just the forwards movement?

You've replaced the props after the crash??

If it was a hard crash then you may have bent the shaft on a motor. This would cause tons of vibration and mess with the IMU.

At the base of the motor bell, there is a small gap between it and the arm. Check each of the motors by spinning them and seeing if this gap remains consistent or closes up and then opens out again. If it doesn't remain consistent whilst you spin the motor then you've damaged a shaft. Check them all. It can be difficult, a feeler gauge may help.

If this isn't the case then you may have damaged something internal.

Personally, I would not fly it. It's damaged and isn't flying correctly. I would say you're chances of it plummeting are high than normal.

 

[Adrian_M]

How is it unstable? Twitching and wiggling all over the place? Or just the forwards movement?

You've replaced the props after the crash??

If it was a hard crash then you may have bent the shaft on a motor. This would cause tons of vibration and mess with the IMU.

At the base of the motor bell, there is a small gap between it and the arm. Check each of the motors by spinning them and seeing if this gap remains consistent or closes up and then opens out again. If it doesn't remain consistent whilst you spin the motor then you've damaged a shaft. Check them all. It can be difficult, a feeler gauge may help.

If this isn't the case then you may have damaged something internal.

Personally, I would not fly it. It's damaged and isn't flying correctly. I would say you're chances of it plummeting are high than normal.

 

[Adrian_M]

Thanks so much for this.

i didn't change the props, there is only very minor damage to them - a few scratches.

it's not really twitching or wiggling, just moves forward slowly, it's like the drone is a bit drunk. i just thought - could this also be due to the fact i did not re-calibrate the compass when i flew it after the crash (i was more concerned about just getting it going to see if it would).

the base of the motor bell seems to the naked eye (i don't have a feeler gauge) to be in line, the gap appears to remain consistent.

is there any way to diagnose internal faults? i called some drone shops in London and they won't touch it - no staff are trained to deal with DJI products.

i'm hoping to be able to take it on holiday in 3 days time

 

[Blacksails]

Ah, doesn't sound like the shafts are bent then. Massive vibration would be seen and heard.

Unfortunately, unless the repair shops are OK'd by DJI (and most aren't) they can't work on them without voiding warranty.

Are you sure you had gps lock when you attempted to fly the second time? If it wasn't locked into sats it would be in Atti mode which drifts. That would be a simple mistake to make if being eager to test after a crash.

Try a compass recalibration. See if it helps. Also, just for the sake of it try a fresh set of props. Very unlikely but you never know.

Bare with me, I'm just riffing on random thoughts of what it might make sense being...

There may be an accelerometer (acc) issue. The accelerometer detects the aircrafts attitude (which way it's leaning) and compensates for that to bring it back level... it's what makes the drone snap back to level when you let go of the sticks in Atti. Theoretically a bad bump could knock the acc slightly. If the acc is then leaning fractionally backwards it would tilt the aircraft forwards to compensate.... but then again I don't know how it's mounted in the mavic and I suppose flying in gps would correct this yet again anyway. In this case I would give an IMU calibration a try.

Also, just double check your transmitter. Have you calibrated the sticks??