THE DREADED YAW DRIFT. Seems many have this where...

Joined
Sep 24, 2017
Messages
113
Reaction score
22
Age
55
My P4P drifts to the left instead of flying straight forward when I command forward flight.. Watch


This was not my video or drone but this is EXACTLY what is going on. I have done everything in this thread nothing works. Any Ideas?
 
Joined
Feb 23, 2014
Messages
683
Reaction score
166
Location
Santa Barbara County, California, USA
Is it possible that the strong cross wind is blowing you off course?
 
Joined
Apr 28, 2017
Messages
399
Reaction score
178
Age
30
Location
TX
My friend, you have encountered the main issue that has plagued V2.0 users. I had the same issue with mine. You can look through the various threads here by searching “yaw drift” and find where some of the gurus went thru my flight logs and found a YAW/magYaw separation in the data. They believed the flight controller was holding one or the other value fixed and rotating the drone until the values matched.

I finally received a new replacement P4P V2 a couple weeks ago, i had to send it off twice. First time it was sent back to me saying “no issue”. I prodded their engineers with the flight log findings of the gentlemen here and they asked me to send it back. At that time they deemed the GPS module was bad and replaced my drone. I havent flown it to see, i was just going to unload it and try to find a V1. Never had an issue there. I hope youre still in the warranty period, and maybe that ive helped.
 
  • Like
Reactions: Curt47
Joined
Oct 24, 2018
Messages
1,182
Reaction score
784
I was lucky. My v2.0 came with the ESC broken. Sent it to DJI and the new bird they sent me has never given me any problems.
 
Joined
Jun 3, 2019
Messages
7
Reaction score
0
Age
31
Location
Pennsylvania
Know the feeling. Mine had some sort of issue similar to this and got progressively worse. ended up drifting right into treetops trying to get a shot. Now I own a mavic 2 pro. waiting for rain to stop to see how it is.
 
Joined
Apr 28, 2017
Messages
399
Reaction score
178
Age
30
Location
TX
After reading this i went and flew my “new” P4P V2 and it began to yaw drift within 15 secs of ascent. There is no hope for this model. Going back to DJI again
 
  • Like
Reactions: oldentimes
Joined
Sep 24, 2017
Messages
113
Reaction score
22
Age
55
Hey thanks everyone. I will be sending it back. This is actually one I had repaired. Before repairs it flew straight. I am covered under DJI Care Refresh. So we will see.
 

sar104

Dic mihi solum facta, domina.
Premium Pilot
Joined
Mar 22, 2014
Messages
5,305
Reaction score
2,700
Location
Los Alamos, NM.
My P4P drifts to the left instead of flying straight forward when I command forward flight.. Watch


This was not my video or drone but this is EXACTLY what is going on. I have done everything in this thread nothing works. Any Ideas?

When you apply forward elevator in P-GPS, the FC attempts to fly a course that matches the aircraft heading - i.e. it should fly in the direction that it is facing. Assuming that the aircraft heading (yaw) actually matches the camera view (i.e. the gimbal is aligned with the aircraft), then it should move in that direction. That's achieved by applying additional negative pitch (forward tilt) relative to the attitude while hovering, and then applying roll corrections if the track diverges from the desired course. The track is computed from the IMU data corrected by the GPS data.

When that doesn't work, as is clearly the case here, there are only a couple of possible causes. Bad GPS data could cause issues, but that's very unlikely to result in a constant course offset. The obvious mechanism is simply that the aircraft has its heading (yaw) incorrect - in other words it is not facing in the direction that it thinks it is. In your examples above, if the IMU yaw value were off by 5° to the left, then that would be the course that the FC attempted, and succeeded, in flying.

The IMU yaw value is initialized at startup from the compass data, which requires a couple of things to go right. Firstly, the aircraft needs to be powered up at a location with no external magnetic interference, so that all the compass sees is the earth's magnetic field (plus the aircraft's magnetic field - but that is subtracted out during calibration). Secondly, it needs to know the local magnetic declination so that it can convert its magnetic heading to a true heading. That's achieved with a global magnetic declination model in the firmware. Interestingly, the P2 shipped with an incorrect model that caused somewhat similar issues, but that doesn't necessarily imply that this is the same problem.

It's impossible to diagnose further without one of the DAT files - the smaller mobile device DAT file is good enough. That contains the raw compass data, the magnetic declination calculation, and the resulting IMU yaw calculation, and should show unambiguously why it is not flying straight.
 
Joined
Jul 29, 2016
Messages
443
Reaction score
229
Age
78
Looking at the video only without any telemetry, the drone is actually pointed in the right direction but is drifting left. The bird is drifting left holding the correct direction.

Two possibilities - there is a strong wind from the right side pushing the drone to the left, or the right hand joystick isn’t properly centered in the left-right axis.

Try flying a tap and fly intelligent flight and see what happens. A waypoint flight would provide the same information. Also try identifying the wind direction, and try a flight parallel to it.
 
Joined
Oct 24, 2018
Messages
1,182
Reaction score
784
As a fellow v2 flyer, I can tell you it isn't wind. A wind strong enough to push the drone sideways would reflect in the video. That video is steady. You also don't see any movement on the trees in any of the passes.
 
  • Like
Reactions: Blade4
Joined
Jul 29, 2016
Messages
443
Reaction score
229
Age
78
As a flyer of a P3 and P4, I can tell you that in a steady sideways wind both will drift smoothly sideways with a perpendicular wind. The only time you see camera motion at all is with strong gusts.
 
  • Like
Reactions: Blade4
Joined
Sep 24, 2017
Messages
113
Reaction score
22
Age
55
When you apply forward elevator in P-GPS, the FC attempts to fly a course that matches the aircraft heading - i.e. it should fly in the direction that it is facing. Assuming that the aircraft heading (yaw) actually matches the camera view (i.e. the gimbal is aligned with the aircraft), then it should move in that direction. That's achieved by applying additional negative pitch (forward tilt) relative to the attitude while hovering, and then applying roll corrections if the track diverges from the desired course. The track is computed from the IMU data corrected by the GPS data.

When that doesn't work, as is clearly the case here, there are only a couple of possible causes. Bad GPS data could cause issues, but that's very unlikely to result in a constant course offset. The obvious mechanism is simply that the aircraft has its heading (yaw) incorrect - in other words it is not facing in the direction that it thinks it is. In your examples above, if the IMU yaw value were off by 5° to the left, then that would be the course that the FC attempted, and succeeded, in flying.

The IMU yaw value is initialized at startup from the compass data, which requires a couple of things to go right. Firstly, the aircraft needs to be powered up at a location with no external magnetic interference, so that all the compass sees is the earth's magnetic field (plus the aircraft's magnetic field - but that is subtracted out during calibration). Secondly, it needs to know the local magnetic declination so that it can convert its magnetic heading to a true heading. That's achieved with a global magnetic declination model in the firmware. Interestingly, the P2 shipped with an incorrect model that caused somewhat similar issues, but that doesn't necessarily imply that this is the same problem.

It's impossible to diagnose further without one of the DAT files - the smaller mobile device DAT file is good enough. That contains the raw compass data, the magnetic declination calculation, and the resulting IMU yaw calculation, and should show unambiguously why it is not flying straight.
OK I'll work on getting some data from my bird up for us all to see here.
 
Joined
Sep 24, 2017
Messages
113
Reaction score
22
Age
55
As a flyer of a P3 and P4, I can tell you that in a steady sideways wind both will drift smoothly sideways with a perpendicular wind. The only time you see camera motion at all is with strong gusts.
yup this video that I posted here is not me or my bird but is the same exact thing that's happening.

This is also happening with no wind. So I've got some kind a directional issue going on and I will work to get some data up.
 
Joined
Oct 24, 2018
Messages
1,182
Reaction score
784
As a flyer of a P3 and P4, I can tell you that in a steady sideways wind both will drift smoothly sideways with a perpendicular wind. The only time you see camera motion at all is with strong gusts.
Wind is never constant, but on the video the movement was. Either way, OP just stated that it does it in 0 wind as well.
 
Joined
Jun 18, 2019
Messages
16
Reaction score
12
Age
49
Hello all.
This is my first post here and I joined because of this topic.

A short bit about myself. I have been flying radio control since 1992 and radio control cars since 1984 and DJI Phantoms since 2015. So definitely not new to the hobby.

I have had this yaw drift from day one with the p4pv2. I regret upgrading from my p4p. There was a firmware update that fixed some of the issues but never corrected the yaw drift entirely. I would correct as best as I could manually in flight.

The yaw drift is not only in forward flight either. Performing a manual POI with every other aircraft has not been a problem. With this p4pv2 it has proven impossible. I fly a friends p4p the other day for the first time in a long time.......and a manual POI was effortless.

I do not know what the fix is. But I have read for some time now this is a wide spread issue. I am getting ready to ditch this p4pv2 and get back into the original p4p.
 
  • Like
Reactions: DKG13CC

sar104

Dic mihi solum facta, domina.
Premium Pilot
Joined
Mar 22, 2014
Messages
5,305
Reaction score
2,700
Location
Los Alamos, NM.
Looking at the video only without any telemetry, the drone is actually pointed in the right direction but is drifting left. The bird is drifting left holding the correct direction.

Two possibilities - there is a strong wind from the right side pushing the drone to the left, or the right hand joystick isn’t properly centered in the left-right axis.

Try flying a tap and fly intelligent flight and see what happens. A waypoint flight would provide the same information. Also try identifying the wind direction, and try a flight parallel to it.

If the wind were strong enough to push the aircraft left then it wouldn't be able to hold position in the hover. The same problem applies to the stick calibration issue - if the aileron were incorrectly zeroed at center then the aircraft would fly left with sticks centered, which it clearly doesn't. It's much more likely to be a compass/yaw issue.
 
  • Like
Reactions: Ansia
Joined
Jun 18, 2019
Messages
16
Reaction score
12
Age
49
My friend, you have encountered the main issue that has plagued V2.0 users. I had the same issue with mine. You can look through the various threads here by searching “yaw drift” and find where some of the gurus went thru my flight logs and found a YAW/magYaw separation in the data. They believed the flight controller was holding one or the other value fixed and rotating the drone until the values matched.

I finally received a new replacement P4P V2 a couple weeks ago, i had to send it off twice. First time it was sent back to me saying “no issue”. I prodded their engineers with the flight log findings of the gentlemen here and they asked me to send it back. At that time they deemed the GPS module was bad and replaced my drone. I havent flown it to see, i was just going to unload it and try to find a V1. Never had an issue there. I hope youre still in the warranty period, and maybe that ive helped.
Could you please direct me to whomever these guru's are so the may be able to help me read the flight logs.
I would love to know if your replaced GPS modual has fixed the problem.
 
Joined
Apr 28, 2017
Messages
399
Reaction score
178
Age
30
Location
TX
Could you please direct me to whomever these guru's are so the may be able to help me read the flight logs.
I would love to know if your replaced GPS modual has fixed the problem.

Sar104 (who has posted in this thread) and BudWalker.

See post 6 I already flew the new Phantom and its yaw drift was observed less than 15secs into the first flight. I, like you, regret ever getting rid of my V1 for this machine.
 
Joined
Jun 18, 2019
Messages
16
Reaction score
12
Age
49
Sar104 (who has posted in this thread) and BudWalker.

See post 6 I already flew the new Phantom and its yaw drift was observed less than 15secs into the first flight. I, like you, regret ever getting rid of my V1 for this machine.
That is a horible to hear the replaced GPS did not correct the problem.

Thanks for the guidance to the flight log guru's.
Maybe some day DJI will address the problem.
It did however take them almost 7 months to correct the 106 firmware release that grounded the p4 standard. So I guess we shall see.

Thanks again.
 

sar104

Dic mihi solum facta, domina.
Premium Pilot
Joined
Mar 22, 2014
Messages
5,305
Reaction score
2,700
Location
Los Alamos, NM.
That is a horible to hear the replaced GPS did not correct the problem.

Thanks for the guidance to the flight log guru's.
Maybe some day DJI will address the problem.
It did however take them almost 7 months to correct the 106 firmware release that grounded the p4 standard. So I guess we shall see.

Thanks again.

I'm really not sure that I count as a guru, but I'm fairly experienced at diagnosing flight problems from txt and DAT logs. In this case we need the DAT files.

Mobile device DAT file: How to retrieve a V3.DAT from the tablet
 

New Threads

Members online

Forum statistics

Threads
140,594
Messages
1,449,132
Members
102,396
Latest member
Henelm