S800 Instability

[Aviator]

O.K I have been trying for weeks to get my S800 flying nice, and have failed.. It still flys terribly! This is mainly noticable when yawing the machine will drift a few meters then start flashing white lights at me... I have been out again testing and found that if I yaw more aggresively the machine drops in one corner and of course then drifts in that direction and causes the white lights and instability. I am assuming this is a hardware fault? or does this happen to anyone else?
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[BorisS]

When does this drifting off happen in gps or attitude mode ? Do you fly it in manual mode does it also happen there ?

Was there ever something altered on the frame like motors or ESCs exchanged ? Arm reinforced etc.

If it only happens in gps and attitude mode were is the gps unit mounted ? If you recalibrate the compass does it calibrate correctly right away or with problems ?

 

[Aviator]

Hi Boris, I haven`t tried flying this one in any other mode than GPS? I will try today in manual and atti, although it will probably drift in those modes anyhow, without a position hold active.. But I will look for one side dropping when I yaw. Nothing has been changed on the airframe the only thing I have done is balance the motors and props..

UPDATE:
I have flown it today and it appears to be slightly better? I have swapped two arms around and defaulted all settings and started again, the settings are all around 220 now apart from the atti settings which are at 100. There is still a fair bit of drift and the machine drops the back end on aggresive yawing still it does this in all modes including manual, although not so noticible in manual but then the yaw is not so aggresive in that mode either. Still getting a sqealing noise and motor pulsing mainly in around 15mph + flight.. Its the sort of sound you get when the timing is wrong on the motors and you open the throttle up full and they squeal and stop

 

[BorisS]

hmmm i wouldn't fly it anymore ! Make a video and send it to your dealer and DJI support ! To me it sounds like a problem with the motors ! Ball bearings or motors loosing RPM due to an issue with them !

Please also upload a video help to diagnose what actually happening and helps other that might have a similar issue at some point !

Thanks

Boris

 

[Aviator]

Yeah will get some footage off it when I have someone around to film it...

 

[Aviator]

Just been out again and have noticed that if I hold in a little roll I can make the machine yaw perfectly? its almost as though one motor is slower than the rest at times, I think I will increase pitch and roll I to multiply the error further..

 

[BorisS]

does it drift off in a straight line when you don't hold roll, or does it drift of in a spiral form ?

It if doesnt drift of in a straight line when yawing, than i also suspect a motors or ESCs more a motor

Boris

 

[Aviator]

does it drift off in a straight line when you don't hold roll, or does it drift of in a spiral form ?

It if doesnt drift of in a straight line when yawing, than i also suspect a motors or ESCs more a motor

Boris

It drifts in a spiral form until I add a little roll and then it works fine... So it narrows things down to three motors. The bearings all seem fine on the motors, I suppose the only way to check which motor is out of sync would be with a tacho and the machine pinned down? unless I can think of another way

 

[BorisS]

hmmm it spirals out no matter in which direction you yaw ?

If it only in one direction yes it narrows it down to three, but couldn't you check by rearranging this three arms. Always take of straight yaw and see in which direction is spiral off. Should at some point give you the info which arm it could be.

Be aware though if something is already wrong anything can happen. Every test you give it in the air is a risk !

Boris

 

[Kilby]

I just saw a few folks on rcg reporting the same problem in the wookong thread yesterday.