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M2P mostly ascending/descending, sometimes going forward/reverse by itsekf

afarkas

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Jan 30, 2019
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Slovakia
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attila-farkas.sk
#1
Hi,
I experienced today a very strange behavior of M2P...
I was howering abow water some 2 meters and suddenly mavic started to descend... Luvky i was just watching and could quivkly bring him up. But even after bringing him up it started to descend immediatelly again.
After while it started to ascend by itself.
I noticed that nearly always i start to fly forward, it starts to descend...
Now it started to fly even forward and reverse - very slowly...
(it was in tripod mode)

Anyone else experienced this?
What can be the problem?

There was little wind and cca 10 grades of celsius...
 
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afarkas

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attila-farkas.sk
#2
So... now i even crashed the aircraft... (no damage) ... i was flying in P mode straight forward in altitude of some 60cm above the ground.
When i let off the stick to stop - M2P stopped and immediately started to crab to the right and just hit a tree some 150cm away.

These are the conditions that were met when this strange behavior took place:
- The take off place was higher than the actual operating space where anomalies occured
- Was flying above water (the surface of the water was very calm)
- GPS on the tablet was ON
- Strong wind in the area, but the operating space was in wind-shadow (anyways can the strong wind around affect the barometer and cause the altitude anomalies?)
- Was flying wit DJI GO 4, but DJI Pilot was installed on the tablet as well, but not launched

Can anything of these cause this anomalies?

Thanks
 

paulatkin73

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#3
how many sats did you have on the gps count? if less than 7 - it may have been one reason. other than that - try to do an IMU calibration and review logs, it is difficult to guess.
with bad gps signal vehicle may exhibit weird movements as it gets told by the gps that its position constantly changes. dji got very good gps receivers - my diy models usually get 7-8 sats in 30sec time and mavic gets 13-14. you need to let it hook up with enought satellites prior to take off. and make sure you have enough of the clear sky above and not in the 'tunnel' or in the gazebo where you may have gps reflections or issues.

but, if the movement was a straight line sideways - it is not very likely a gps issue.
 

afarkas

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attila-farkas.sk
#4
how many sats did you have on the gps count? if less than 7 - it may have been one reason. other than that - try to do an IMU calibration and review logs, it is difficult to guess.
with bad gps signal vehicle may exhibit weird movements as it gets told by the gps that its position constantly changes. dji got very good gps receivers - my diy models usually get 7-8 sats in 30sec time and mavic gets 13-14. you need to let it hook up with enought satellites prior to take off.

but, if the movement was a straight line sideways - it is not very likely a gps issue.
Yes, it had 14 sats. And the crabbing took place immediately as it stopped the forward movement...
 

paulatkin73

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#5
Yes, it had 14 sats. And the crabbing took place immediately as it stopped the forward movement...
so, you know that you can kill motors in the air by moving sticks together - it should work. over some tall grass or somethign soft it should not cause much damage, so, i would try to recalibrate imu and compass and try again, carefully, in the tripod mode first, at minimum altitude and be ready to kill it.
obviously, do not do it over the concrete and close to anything.
 

afarkas

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#6
so, you know that you can kill motors in the air by moving sticks together - it should work. over some tall grass or somethign soft it should not cause much damage, so, i would try to recalibrate imu and compass and try again, carefully, in the tripod mode first, at minimum altitude and be ready to kill it.
obviously, do not do it over the concrete and close to anything.
Well, actually im not sure whether i can or can not kill the motors... i wrote about it in an other thread... as i have custom sticks mode, i can not start the motors with sticks - it just does not work... so i am not sure whether it will work to stop them...
But anyways - it was so quick i had not even time to react by pulling the stick to crab oposite way... it was just - my eyes went wide and the drone was on the ground :D
Im glad there was no damage (i was low and slow)
But im going to recalibrate the beast
thanks

(BTW - just after that crash i uninstalled the DJI Pilot app, so there was the DJI GO only and made a test flight... well - it was not lower than the takeoff level and it was not above water, but no anomalies anymore...)
 
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paulatkin73

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#7
Well, actually im not sure whether i can or can not kill the motors... i wrote about it in an other thread... as i have custom sticks mode, i can not start the motors with sticks - it just does not work...
i saw also there were some bugs in the apps/code in those modes. you sure you do not want to use mode 2? it is what it is, of course, but, it would be a path of a least resistance, as mode 2 usually works everywhere OK - as it is the most usual one.
 
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afarkas

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attila-farkas.sk
#8
i saw also there were some bugs in the apps/code in those modes. you sure you do not want to use mode 2? it is what it is, of course, but, it would be a path of a least resistance, as mode 2 usually works everywhere OK - as it is the most usual one.
i can not use mode2 - i woul crash the craft immediately... all my life "PULL" means "pull UP" ... its already a reflex deep in me... if i use mode 2 i will shot the craft to the ground at the first ocasion i will need to increase altitude
 
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