DJI S800 yaws in flight

[Javajack]

I have more than 100 flying hours on an S800 doing aerial photography. Recently it has begun yawing right or clockwise under high throttle conditions. This usually happens when I am chasing a vehicle for a television commercial or something, flying low to the ground to track it at high speed. Of course this is disconcerting and dangerous, but I don't know what is causing this. Any ideas? It doesn't happen all the time and I used to think it was during lower battery conditions but last night it happened with a brand new battery.

I cannot feather it or joystick to the left enough to compensate and have to rise up and regain control. Does this sound like a motor that is failing, or is this a flight control issue? I'm at a loss. We've actually bridge across our arm contacts as they kept wearing out, especially with a copter that's getting this old. So, every motor is getting full supply voltage.

Would appreciate any good feedback.

Jack Tunnicliffe
Java Post Aerial Photography
www.javapost.ca

 

[Benjamin Kenobi]

Are the little spacers under the motors in the correct position? One on the wrong side could cause this.

Otherwise I'm at a loss. :02.47-tranquillity:

 

[Javajack]

Thanks, we're going to check this out. We got the same suggestion from one of our suppliers, too. Just bringing it into the shop now. I'll let you know what we find. Thanks for the help.

 

[gtranquilla]

Speculating here....

External possibilities: cross wind (FC yaw control and/or motors can't remain ahead of the yaw heading) possibly due to cross-winds etc.
Payload profile is not a symmetrical drag to the oncoming wind.

Internal:
1) Issue with one motor and/or prop or 3 deg motors spacers not inserted correctly. swap motors/prop to troubleshoot by process of elimination.
Examine iOSD flight data on the motors to gain perspective on which motors are spinning faster in straight forward flight.



If you have the iOSD including your problem flight data, check out the graphics on the motors to see if any are struggling harder then the others.....

I have more than 100 flying hours on an S800 doing aerial photography. Recently it has begun yawing right or clockwise under high throttle conditions. This usually happens when I am chasing a vehicle for a television commercial or something, flying low to the ground to track it at high speed. Of course this is disconcerting and dangerous, but I don't know what is causing this. Any ideas? It doesn't happen all the time and I used to think it was during lower battery conditions but last night it happened with a brand new battery.

I cannot feather it or joystick to the left enough to compensate and have to rise up and regain control. Does this sound like a motor that is failing, or is this a flight control issue? I'm at a loss. We've actually bridge across our arm contacts as they kept wearing out, especially with a copter that's getting this old. So, every motor is getting full supply voltage.

Would appreciate any good feedback.

Jack Tunnicliffe
Java Post Aerial Photography
www.javapost.ca

 

[soler]

I have more than 100 flying hours on an S800 doing aerial photography. Recently it has begun yawing right or clockwise under high throttle conditions. This usually happens when I am chasing a vehicle for a television commercial or something, flying low to the ground to track it at high speed. Of course this is disconcerting and dangerous, but I don't know what is causing this. Any ideas? It doesn't happen all the time and I used to think it was during lower battery conditions but last night it happened with a brand new battery.

I cannot feather it or joystick to the left enough to compensate and have to rise up and regain control. Does this sound like a motor that is failing, or is this a flight control issue? I'm at a loss. We've actually bridge across our arm contacts as they kept wearing out, especially with a copter that's getting this old. So, every motor is getting full supply voltage.

Would appreciate any good feedback.

Jack Tunnicliffe
Java Post Aerial Photography
www.javapost.ca

i have the same issue, at full forward after 50-60m it can saddlery yaw one way or another. It seams to happen fast not a gental yaw. Is this the same problem you are having? Using A2 FC.

 

[gtranquilla]

In the case of my Basecam BGC, the camera yaw axis was drifting until I was able to re-calibrate the IMU gyroscope...... then the issue disappeared.

I assume that the FC IMU gyros are in need of recalibration.

 

[koptercam]

I have more than 100 flying hours on an S800 doing aerial photography. Recently it has begun yawing right or clockwise under high throttle conditions. This usually happens when I am chasing a vehicle for a television commercial or something, flying low to the ground to track it at high speed. Of course this is disconcerting and dangerous, but I don't know what is causing this. Any ideas? It doesn't happen all the time and I used to think it was during lower battery conditions but last night it happened with a brand new battery.

I cannot feather it or joystick to the left enough to compensate and have to rise up and regain control. Does this sound like a motor that is failing, or is this a flight control issue? I'm at a loss. We've actually bridge across our arm contacts as they kept wearing out, especially with a copter that's getting this old. So, every motor is getting full supply voltage.

Would appreciate any good feedback.

Jack Tunnicliffe
Java Post Aerial Photography
www.javapost.ca

Hey Jack,

Very interesting you mention this, as I am coming across the similar issue at the moment. It usually happens when im on less than 50% battery voltage around the 21.5v - 22.0v and mostly when descending. I thought it could be a battery issue also, however on new batteries it can do the same.

Usually i can hear when its about to happen, and then it yaws to the left (ccw) sometimes doing a full 360 rotation. during the rotation, it also has the tendency to drop in altitude and have now power to lift for a couple seconds until it stops its spin.
I have checked all the spacers and everything is correct there.
I am running Graupner 14x8 props, so it could be theres a prop that is slipping. so im going to try some new prop adapters that have anti slip pads (t-motor), however I dont understand that it is only happening at the low voltage.

Because of this, we have been landing at 22.0v so basically losing 20% of our flight times.

-Marco

 

[sk8brd]

there been a few s800 evo owners that have experienced and reported this problem. the theory is that under high throttle like fast forward flight the motors are almost peaked out with not much available power or thrust left and even though in atti/gps the fc limits the throttle to less then 100% for stability purposes there just isn't enough power in the motors at their auw to control the craft at high speed so it spins out. These were all a2 evo's- and their auw was at the upper limit described by dji specs. one guy replaced all arms and his battery connection with ec5's and said it got better but didn't solve it 100% so he doesn't fly full out anymore.

 

[flappybird]

I've had this problem from day one. On the first version of A2 software I was a able to reach speeds of up to 27m/s (tail wind + using a decent to pick up speed) and the "spin outs" would happen randomly at speeds as low as 12m/s (higher altitude or a head wind). From all my research and communications with other S800 owners I've come to the same conclusion as SK8brd this is an inherent problem with the S800's "propulsion system" it's essentially under geared. The problem becomes much more visible at higher altitudes, and when batteries begin to age which results in additional voltage sag and less power to the motors. They all seem to spin to the right which might just be the A2 purposefully compensating for the lack of lift. The problem will not result in a crash as long as you have some extra distance between the bird and everything else, but it's a giant PITA and will make you fearful of proximity flying and anything high speed in general.

Solution #1 Buy The S1000. Then you can enjoy pegging the sucker to its maximum (new A2 2.3 Frimware limitation) allowable 20m/s while enjoying a perfect experience every time.

Possible Solution #2 Something I just recently found out about but and is not tested is to buy this KDE triple propeller adapter: http://www.kdedirect.com/KDEXFTPAV2.html This will essentially give the S800 what its missing if it works.

Good luck

 

[gtranquilla]

Whereas the flight computer may be sending the right output in a timely manner to maintain a straight forward heading without any yaw, the rest is up to the ESCs to respond quickly enough. But more importantly, the motor/prop combos have to have the speed/torque characteristics to enable almost instantaneous speed change across the speed range. That is likely not possible at the high end. Also the AUW increased with heavier payloads there is a shifted position on the motor speed/torque curve such that speed change can become more difficult. In such a situation props with less pitch and/or less diameter would help but then we know where that ultimately leads us!

So IMHO - Its a laws of Physics issue and not the firmware.

there been a few s800 evo owners that have experienced and reported this problem. the theory is that under high throttle like fast forward flight the motors are almost peaked out with not much available power or thrust left and even though in atti/gps the fc limits the throttle to less then 100% for stability purposes there just isn't enough power in the motors at their auw to control the craft at high speed so it spins out. These were all a2 evo's- and their auw was at the upper limit described by dji specs. one guy replaced all arms and his battery connection with ec5's and said it got better but didn't solve it 100% so he doesn't fly full out anymore.

 

[flappybird]

gtranquilla

Do you think the 3 prop fix could help? I've considered purchasing but the experiment would set me back about $300 so I've been hesitant.

I've even considered this for my S1000 but only for high altitude above 12,000ft as it wouldn't be necessary for anything lower

 

[gtranquilla]

Sorry I don't know....wish I did though.

 

[Javajack]

Thanks for all your help on this, guys. Sounds like it's more of a problem than I had originally realized. The flight data seems to look pretty normal yet even after replacement suspect motors and arms and changing out the IMU, it is still spinning out. Interesting about some having issues when battery voltage is down. I had a battery this morning, definitely not finished, but near the end of a flight, barely able to land due to constant yaw spinning the S800. The yaw right is not as noticeable in Home Lock.

 

[Javajack]

I'm curious about your comment regarding the IMU gyros possibly needing recalibration. We swapped IMU's and there seemed to be little difference. What can one do to check calibration of these units?

 

[PeterLester]

Imu recalibration is in the manual and assistant software advanced section if i recall correctly.


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[Benjamin Kenobi]

Hey chaps,

Thought I should chime in again. My S800 used to yaw in flight sometimes. To be honest the problem just went away one day, not sure why. It only yawed a little bit under hard inputs so it didn't really bother me as I'm a gentle flyer normally. I think it went away after either finding a spacer in the wrong place or re-calibrating the compass. I'm not entirely sure to be honest.

Could it be a solder joint on one of the arm mounts? Maybe check by placing your hand on the little metal plate where it has the X or 0 to see if any are hotter than the others.

What gains are you using on yaw?

Ps - Battery conditions shouldn't affect the MR in any way during the normal phases of discharge.

 

[Javajack]

Because we have so many hours on this machine for aerial photography work we've hard wired around the arm contacts. We could no longer trust these contacts as these oxidize and corrode over time. We'd tried conductive grease for awhile to improve contact but finally we lost a motor in the air and suffered a crash due to lack of contact. At that point we hard wired the arms and haven't had that issue since. We usually run about 160-180 for yaw gain. I'm at 200 right now as a test but plan to put it back to where it was.

 

[Benjamin Kenobi]

Yeah, I've also put a few hundred hours through mine and have had a similar experience to you, although the two times I've lost a motor I just brought it in to land and popped a new arm on (I blamed the ESC to be honest).

I have my yaw gain at 130% so I guess that's not the issue then.

I hope you fix it. Did you say you've tried replacing all the counter-clockwise arms and the problem persists?

 

[Javajack]

We've replaced the suspect arms but not all of them. I was flying early this morning and had no issues until the wind came up, then control issues under GPS where I had a hard time getting the helicopter into the yaw position I wanted for an approach. In these situations I get it just far enough from home to get it into home lock and fly like that. We needed to do a 360 of a building and I wasn't trusting regular gps flying with some wind but the home lock works fine regardless of how much the craft yaws or spins in circles. The Kraken is on it's way with upgraded motors so soon the tired S800 will sit on the shelf as a back-up

 

[Benjamin Kenobi]

Ah, poor old S800. I still love mine but the day will soon be coming when it needs to retire as it will be a couple of years old in the Spring. It has made back the cost of buying it many, many times over now, so I still think it was a great investment.

If you do manage to fix it please let us know. :02.47-tranquillity: