I and one other Phantom 4 Pro owner (so far) have noted an odd and potentially dangerous RTH behavior: Upon either a manually commanded or failsafe RTH the unit will climb continuously while enroute back to home point until it is either stopped by manually exiting RTH, or finally reaches its home point (at which point it will begin a vertical decent.) As far as we can tell the unit will ascend continuously until stopped, or at least we haven't experienced a limit. The pre-set RTH altitude setting seems to have no effect on this behavior.

This is obviously a serious bug since it could potentially cause loss of the aircraft and/or present a danger to other air traffic. The problem may not be noticed over short horizontal distances but over longer routes it is dramatic.

More discussion here:  http://www.phantompilots.com/thr ... ou-seeing-it.97645/

Has anyone else noticed this behavior during RTH on long-distance flights?I'm not sure if this problem affects only a few units or a large number. If you are only flying out a few hundred feet you may not notice it, but as the horizontal distance grows it becomes very apparent.

What did you set for your RTH height (note that the RTH height is in metres) ?

RTH height is set to 30 meters but the setting appears to have no effect when this problem occurs.

nocaps Posted at 2016-12-5 22:42
RTH height is set to 30 meters but the setting appears to have no effect when this problem occurs.

And was that set with all powered up and connected ?

I believe so, but if advisable I will reset the value with the aircraft powered up and connected in order to be certain. However on one example flight the unit gained 500 feet altitude in only 3500 horiziontal feet once RTH was activated, but I do not see that occur if RTH is activated on short flights. If the RTH altitude value was incorrcetly recorded then I would see the effect at all times. Another used has reported the same problem and he saw a 920' altitude increase before he manually terminated RTH.

On my second flight I was at a height of 112 meters, the distance away was 500 meters, I lost complete signal and it went into returning to home mode, I let it fly back on its own for 400 meters, I then took control and landed myself, the height was 113 meters all the way back, my RTH height was set at 70 meters

nocaps Posted at 2016-12-5 22:46
I believe so, but if advisable I will reset the value with the aircraft powered up and connected in order to be certain. However on one example flight the unit gained 500 feet altitude in only 3500 horiziontal feet once RTH was activated, but I do not see that occur if RTH is activated on short flights. If the RTH altitude value was incorrcetly recorded then I would see the effect at all times. Another used has reported the same problem and he saw a 920' altitude increase before he manually terminated RTH.

Sounds like another one for DJIs R&D it should not gain or lose altitude, but there again does the P4P not create its own 3D map to allow it to retrace its original path ?

Aardvark Posted at 2016-12-6 06:59
Sounds like another one for DJIs R&D it should not gain or lose altitude, but there again does the P4P not create its own 3D map to allow it to retrace its original path ?

My flight was at 100-150 feet, I never approached the 650' I saw on the return RTH portion so the unit certainly was not retracing any part of the prior flight. As far as I can tell the altitude was steadily increasing and would have increased even more if the return distance had been further, and that is potentially quite dangerous.  

This should all be clear in the flight logs, if I can figure out how to submit them.

Snowwolfwarrior Posted at 2016-12-5 22:59
On my second flight I was at a height of 112 meters, the distance away was 500 meters, I lost complete signal and it went into returning to home mode, I let it fly back on its own for 400 meters, I then took control and landed myself, the height was 113 meters all the way back, my RTH height was set at 70 meters

That's what I would expect from my P4, if it's above the RTH set height when RTH initiated then it will stay at that height.

Aardvark Posted at 2016-12-6 07:14
That's what I would expect from my P4, if it's above the RTH set height when RTH initiated then it will stay at that height.

Yes, that is normal behavior, RTH will occur at your current altitude or the preset RTH altitude, whichever is higher.

Would you please sync your flight records through APP?
Then please let us know your APP account username (E-mail address), and the certain time it happened, we'll check the data.

I had mine go up to 900 ft even though I had the RTH setting at 400

Aardvark Posted at 2016-12-5 23:14
That's what I would expect from my P4, if it's above the RTH set height when RTH initiated then it will stay at that height.

Yes that is what I would expect, I was answering the question from the op that mine returned home and stayed at the exact same level it started off at and never increased in height in the 400 meter distance

Seems like all Phantoms ascend or descent while RTH.....

http://forum.dji.com/forum.php?m ... mp;page=1#pid594762

Check your flight log and the records for throttle, maybe somebody (you) pushed the Throttle stick Upwards all the way back home.
Could you please post here your flight log TXT and the recording of the Throttle stick while RTH-Ascending?

Thanks in Advance.

DJI Natalia Posted at 2016-12-6 15:45
Would you please sync your flight records through APP?
Then please let us know your APP account username (E-mail address), and the certain time it happened, we'll check the data.

Hi Natalia,

I am attempting to reply to your question but I cannot seem to send you a personal message via the forum. Can you PM me and then I will respond with the information, or provide an email address I can use?

Thanks

donogl Posted at 2016-12-6 18:04
Seems like all Phantoms ascend or descent while RTH.....

http://forum.dji.com/forum.php?mod=viewthread&tid=74256&page=1#pid594762

This incident is unrelated to this thread, which involves uncommanded RTH altitude increase of the Phantom 4 Pro. Please let's not clutter it up with miscellaneous RTH issues from other models.

Sorry but my Thread  involves uncommanded RTH altitude decrease of the Phantom 4 and nobody can explain it to me and just points the finger on me like it was my fault.
I am trying realy to get some more information and it could be maybe a similar issue / reason for that out of the software.

Could you upload you flightlog.txt here and post the link.
http://www.phantomhelp.com/LogViewer/Upload/

I just wanted to see what your log says during the uncommandet rising during rth for throttle stick value.
Thanks in advance for your help.

nocaps Posted at 2016-12-7 00:44
Hi Natalia,

I am attempting to reply to your question but I cannot seem to send you a personal message via the forum. Can you PM me and then I will respond with the information, or provide an email address I can use?

I've tried to PM you, but not sure whether you could receive it.
And your APP account is the same e-mail address you used on forum or not?

DJI Natalia Posted at 2016-12-7 11:27
I've tried to PM you, but not sure whether you could receive it.
And your APP account is the same e-mail address you used on forum or not?

Hi Natalia,

Yes, the email address is the same for APP account and forum. I was able to successfully reply to your PM and there is more information there.

Thanks

donogl Posted at 2016-12-7 02:19
Sorry but my Thread  involves uncommanded RTH altitude decrease of the Phantom 4  and nobody can explain it to me and just points the finger on me like it was my fault.
I am trying realy to get some more information and it could be maybe a similar issue / reason for that out of the software.

But I thought yours didn't decrease, didn't it just stop RTH climb because you hit down on the throttle?  

Back to the P4P issue...

I tried a few things, including calibrating the IMUs and re-setting the RTH altitude value (with aircraft connected) to another value and then back to the desired value just in case the stored value was somehow corrupted. No change however, every long mission (maybe a mile) resulted in the aircraft climbing steadily upon entering RTH mode (to well above the preset value), and kept climbing until I halted it by manually exiting RTH.

This means that RTH is potentially dangerous on long missions until the bug is fixed. I don't think this is a hardware problem with my particular unit as the aircraft flies perfectly otherwise. I imagine that once DJI has confirmed the issue that it will be corrected promptly due to the possible danger to other aircraft. It is very easy for an unknowing operator to not realize what is happening and inadvertently fly much higher than intended.

I should note that on shorter flights RTH works perfectly (and the precision landing feature seems to work amazingly well BTW) so if you have only flown short missions and haven't seen the problem and thus think you don't have it, I'd think again or make sure you verify all is OK before you attempt to use RTH at longer distances with the P4P.

DRONE-flies-YOU Posted at 2016-12-8 04:22
OK, I may know what this is.  

This is the OA trying to CLIMB over a gigantic obstacle - even if the drone is 400 feet up.  My OA goes bat-crap crazy when I'm at the controls in P-mode and it's flying into a shadow-obscured background.  It beeps & does all the OA warning stuff AND STOPS THE DRONE.  Let go of sticks so it looks straight & level - NO on-screen radar bars, ok try again.  1 second later, stops.  Rinse/repeat.  There was a very light breeze (tested with ATTI mode) yet I had the high wind warnings like there was a hurricane.  Got it down in SPORT mode (wanted GPS positioning).

No, it has nothing at all to do with OA. The unit was way too high to detect any objects on the ground and all flights were made on overcast days so no shadows at all, and is also easily repatable and behaves the same way each time. The problem is definitely a bug of some kind.

nocaps Posted at 2016-12-7 12:27
No, it has nothing at all to do with OA. The unit was way too high to detect any objects on the ground and all flights were made on overcast days so no shadows at all, and is also easily repatable and behaves the same way each time. The problem is definitely a bug of some kind.

You're right.  This is an isolated issue with only a couple drones, namely YOURS.

What is the Flightlog.txt showing for values for the stick commands during the ascending RTH at the few isolated couple of drones involved in this problem?

donogl Posted at 2016-12-8 05:08
What is the Flightlog.txt showing for values for the stick commands during the ascending RTH at the few isolated couple of drones involved in this problem?

I don't think anyone should keep repeating 'few isolated cases' until they have tested with their own P4P at the ranges mentioned and have seen no problem.

I have reviewed my flight logs and they clearly show no stick input whatsoever during the RTH altitude-increase events.

Ok. Thanks for the info.

nocaps Posted at 2016-12-7 22:59
Hi Natalia,

Yes, the email address is the same for APP account and forum. I was able to successfully reply to your PM and there is more information there.

Thanks, and please export the flight date through Assistant 2, upload it to dropbox, and let me know the link, we will help you create a case for data analysis.

DJI Natalia Posted at 2016-12-9 11:08
Thanks, and please export the flight date through Assistant 2, upload it to dropbox, and let me know the link, we will help you create a case for data analysis.

Hi Natalia,

I sent you a PM with a link to the flight log data.

nocaps Posted at 2016-12-9 12:49
Hi Natalia,

I sent you a PM with a link to the flight log data.

Thanks, I've transferred the data to our engineers, they will analyze it and let you know the result, thanks again for your support.

nocaps Posted at 2016-12-9 12:49
Hi Natalia,

I sent you a PM with a link to the flight log data.

Hi Nocaps, we've checked you flight data, while we need more information to locate the problem.
Please export the corresponding data at the right side of the flight data you have sent to us, then add it to dropbox, I'll transfer that to our engineers again, thanks so much!
Just to confirm, you have synced flight records on your APP successfully, right? how many flights listed there?Besides, did you record at that time or enabled video cache on the APP? if so, please upload the video as well, thanks.

DJI Natalia Posted at 2016-12-10 13:17
Hi Nocaps, we've checked you flight data, while we need more information to locate the problem.
Please export the corresponding data at the right side of the flight data you have sent to us, then add it to dropbox, I'll transfer that to our engineers again, thanks so much!
Just to confirm, you have synced flight records on your APP successfully, right? how many flights listed there?Besides, did you record at that time or enabled video cache on the APP? if so, please upload the video as well, thanks.

Hi Natalia,

I have sent you a PM with the requested information.

Hi Natalia,

I have run another test flight to demonstrate the problem. As you will see, after RTH is initiated the aircraft begins to climb continuously from approximately 25 meters to over 200 meters(!) before finally reaching its home point. The RTH altitude was set at 23 meters. There was no control stick input at all once RTH was initiated. Also the unit seems to work perfectly in all other flight modes (so I don't think this is a hardware problem), only RTH is affected by the problem as far as I can tell. I have created a complete set of .DAT flight log files and also have linked the .TXT log files to my account. I will send you a Dropbox link via PM.


I would suggest that engineering use this new data set as it is complete and unambiguous. I think this should be considered an urgent problem as it can be potentially dangerous to other aircraft as the Phantom operator may not even be aware it is happening.

Hi Natalia,

I also need to report something else I just noted during testing: If the aircraft is below the preset RTH value then upon entering RTH mode it will climb to the preset altitude and return home, just as it should. However if the aircraft is above the preset RTH altitude at the time RTH is initiated then it will continue to climb (rather than hold its current altitude, which I beleve is the expected behavior.) So that may explain why some are seeing the problem and some are not, the problem only seems to occur if you are above your preset RTH altitude when RTH is initiated.

Edit: I have now had two other P4P owners confirm this behavior (uncontrolled ascent if RTH initiated above RTH preset altitude.) The flight logs I uploaded today should clearly demonstate the problem.

nocaps Posted at 2016-12-11 02:59
Hi Natalia,

I also need to report something else I just noted during testing: If the aircraft is below the preset RTH value then upon entering RTH mode it will climb to the preset altitude and return home, just as it should. However if the aircraft is above the preset RTH altitude at the time RTH is initiated then it will continue to climb (rather than hold its current altitude, which I beleve is the expected behavior.) So that may explain why some are seeing the problem and some are not, the problem only seems to occur if you are above your preset RTH altitude when RTH is initiated.

Thank you so much for the test and details again, our engineers are analyzing the data you provided. I'll let you know for any news.

Was there ever a fix for this. I am suffering from the same thing. I press RTH and the drone goes straight upwards. I have mine set to 30 meters. It has reached 100 meters before I stopped it and manually flew it home. I am also worried about this. I have tested it multiple times with the same result. I am running a phantom 4.

Craigrn Posted at 5-26 17:35
Was there ever a fix for this. I am suffering from the same thing. I press RTH and the drone goes straight upwards. I have mine set to 30 meters. It has reached 100 meters before I stopped it and manually flew it home. I am also worried about this. I have tested it multiple times with the same result. I am running a phantom 4.

I don't know about a fix but I've read posts that this problem is often caused by the obstacle avoidance function.  If the P4 thinks something is in front of it, it is programmed to back off a bit and then rise until it believes it is clear of the obstacle.  I've read that direct sunlight will sometimes cause this problem.  You might also have a dirty OA lens.  Make sure it's clean.  Consider disabling obstacle avoidance and testing it.  Good luck.  

Craigrn Posted at 5-26 17:35
Was there ever a fix for this. I am suffering from the same thing. I press RTH and the drone goes straight upwards. I have mine set to 30 meters. It has reached 100 meters before I stopped it and manually flew it home. I am also worried about this. I have tested it multiple times with the same result. I am running a phantom 4.

There are a couple of possible explanations.
Post flight data so we can see what was going on.

Labroides Posted at 5-27 05:42
There are a couple of possible explanations.
Post flight data so we can see what was going on.

How do I do that?

Craigrn Posted at 6-2 17:47
How do I do that?

Go here:
https://www.phantomhelp.com/LogViewer/Upload

Follow the directions and it gives you a summary report for teh flight in question.
Come back and post a link to that report.

I found my issue. I turned off the RTH obstacle check and the RTH worked fine. Do you know if there is a fix for this or do I need to just keep it off. I usually fly at higher altitudes than the trees so if I lose signal and RTH kicks in, I should not have an issue with hitting anything.