Hey guys, I have seen a few posts on this but no resolutions.

I have an old Phantom 4 I use for training and it has recently decided that descending will be done very slowly....  Normal speed is 3m/s or 4m/s sport mode.  This one is 0.3m/s in either mode.  It also randomly climbs quite quickly and if you pull full down it usually stops climbing.

Have refreshed firmware and full recalibaration of sensors twice, calibrated controller and IMU, factory reset etc. No change.  Has no extras on it, tried with down sensors on and off.  I am guessing the flight controller is screwed, but seems a very odd fault.

Anyone had the same and was able to work out what it was?

Hi JustAskDave! DJI Natalia here from DJI Support.  We understand with your concern and we would like to apologize for the inconvenience caused. The DJI Phantom 4 can only fly up to 8 m/s.   I highly suggest you to check the wind strength at that time. If the aircraft flies forward at 8 m/s after fully pushing the control sticks, try to turn the aircraft front or fly it in the reverse direction after fully pushing the control sticks. Check whether it can fly to 10 m/s.   I hope you have got the solution you were expecting. Let me know if you have any other questions and have a nice day ahead!

DJI Natalia Posted at 12-4 19:39
Hi JustAskDave! DJI Natalia here from DJI Support.  We understand with your concern and we would like to apologize for the inconvenience caused. The DJI Phantom 4 can only fly up to 8 m/s.   I highly suggest you to check the wind strength at that time. If the aircraft flies forward at 8 m/s after fully pushing the control sticks, try to turn the aircraft front or fly it in the reverse direction after fully pushing the control sticks. Check whether it can fly to 10 m/s.   I hope you have got the solution you were expecting. Let me know if you have any other questions and have a nice day ahead!

Hey Natalia, thanks for the reply, the issue is the descent speed not normal flying speed.

Normal descent speed is max 3m/s, sport is max 4m/s. Mine descends at max 0.3m/s as indicated on the telemetry and randomly will start climbing at 2 to 3 m/s for no reason.

In google searches I have a couple of others that had similar issues, only one posted theirs was working again after recalibrating the downward facing sensors.  I have refreshed the firmware twice, recalibrated sensors twice, recalibrated IMU and Compass, recalibrated the controller. No change.  

I suspect its stuffed, which is a shame as there is no replacement for these in training (we require a drone with manual switching to Atti mode for licence exams in Australia).

JustAskDave Posted at 12-4 19:47
Hey Natalia, thanks for the reply, the issue is the descent speed not normal flying speed.

Normal descent speed is max 3m/s, sport is max 4m/s. Mine descends at max 0.3m/s as indicated on the telemetry and randomly will start climbing at 2 to 3 m/s for no reason.

Aloha Dave,

      Have you checked DJI Go 4 for the speed controls and limitations by operator.  I seem to recall that Go 4 had them.  My apologies if I am wrong.  The recent software has them, I thought Go 4 did to.

     Take care and be safe!

Aloha and Drone On!

JustAskDave Posted at 12-4 19:47
Hey Natalia, thanks for the reply, the issue is the descent speed not normal flying speed.

Normal descent speed is max 3m/s, sport is max 4m/s. Mine descends at max 0.3m/s as indicated on the telemetry and randomly will start climbing at 2 to 3 m/s for no reason.

If you can retrieve a .DAT, it should be easy to determine what the problem is. The .DAT from the P4 is preferrable but there is a .DAT on the controller as well. Use these

instructions

to see how to retrieve a .DAT.

  

  

It will be large so you will need to use a public sharing site like Dropbox or GoogleDrive.

BudWalker Posted at 12-7 07:59
If you can retrieve a .DAT, it should be easy to determine what the problem is. The .DAT from the P4 is preferrable but there is a .DAT on the controller as well. Use these instructions to see how to retrieve a .DAT.     It will be large so you will need to use a public sharing site like Dropbox or GoogleDrive.

Thankyou BudWalker!  

Setup was a little different to your description, but I got there!  I have downloaded the test flights and file is 392mb, uploaded to a shared google drive.  

I tried looking through the logs but couldnt work out what I was looking at!

https://drive.google.com/drive/f ... bYK-?usp=drive_link

JustAskDave Posted at 12-7 15:29
Thankyou BudWalker!  

Setup was a little different to your description, but I got there!  I have downloaded the test flights and file is 392mb, uploaded to a shared google drive.  

The file you submitted,
EXPORT_FILE_2024-12-08_09-20-19.DAT,
contained 7 .DATs from the P4. None of these were an actual flight where the motors were started. A .DAT gets created every time the P4 is powered up. Looks like 6 of the .DATs were from a power up inside the house since no satellites were acquired. There is one .DAT were it looks like you powered up in the back yard but didn't start the motors. That .DAT got created

2024-12-3 7:29:3 GMT

You're close. DJI Assistant should show the flight date.

BudWalker Posted at 12-7 16:48
The file you submitted,
EXPORT_FILE_2024-12-08_09-20-19.DAT,
contained 7 .DATs from the P4. None of these were an actual flight where the motors were started. A .DAT gets created every time the P4 is powered up. Looks like 6 of the .DATs were from a power up inside the house since no satellites were acquired. There is one .DAT were it looks like you powered up in the back yard but didn't start the motors. That .DAT got created

Hmm, ok that is bizarre..  I did a full firmware refresh, reboot, the recalibration of the sensors, reboot then shut down, then power on and an IMU and Compass Calibration, power off fit propellers then power on and 2 test flights, a 1min and 4 min. When I look at the DJIGo4 app the 2 flights are there.

I will do a single flight later and grab the logs from that and see what it shows.

BudWalker Posted at 12-7 16:48
The file you submitted,
EXPORT_FILE_2024-12-08_09-20-19.DAT,
contained 7 .DATs from the P4. None of these were an actual flight where the motors were started. A .DAT gets created every time the P4 is powered up. Looks like 6 of the .DATs were from a power up inside the house since no satellites were acquired. There is one .DAT were it looks like you powered up in the back yard but didn't start the motors. That .DAT got created

OK, just went and did a test flight, set everything up and powered up and waited for all alerts to go (IMU startup took about 20 seconds then IMU warming up took another 20 or so seconds). Launched, climbed up about 5m with a quick burst of throttle, descended at max descent rate (indicated 0.3ms), repeated, landed, shut down engines, shut down P4, shut down controller.

Hooked it up to DJI Assistant 2 and no logs showing at all from today, just the previous ones already exported.  I hooked up to the phone and downloaded the flight logs from the DJI Go4 app and and have put them into that same folder linked above, including the one from the other day that I had copied from the P4 which this version does show the flights .  It would seem that the P4 is not storing the flight logs?? as they are in the Go4 app...  Very bizarre.

Update, I extracted the Fly DAT files from the previous export and the FLY171.DAT has no flight data, but the Fly171 from the controller does (thats the flight from 3rd Dec). Did the firmware update/refresh screw up the on board storage? (no SD card installed)

JustAskDave Posted at 12-8 14:44
OK, just went and did a test flight, set everything up and powered up and waited for all alerts to go (IMU startup took about 20 seconds then IMU warming up took another 20 or so seconds). Launched, climbed up about 5m with a quick burst of throttle, descended at max descent rate (indicated 0.3ms), repeated, landed, shut down engines, shut down P4, shut down controller.

Hooked it up to DJI Assistant 2 and no logs showing at all from today, just the previous ones already exported.  I hooked up to the phone and downloaded the flight logs from the DJI Go4 app and and have put them into that same folder linked above, including the one from the other day that I had copied from the P4 which this version does show the flights .  It would seem that the P4 is not storing the flight logs?? as they are in the Go4 app...  Very bizarre.

No idea why those .DATs aren’t showing up in Assistant 2. But, if you can get them from the controller please provide those. I don’t see any additional files in the GoogleDrive folder you provided in post #6.

  
  

FLY171.DAT doesn’t show a motor start or any stick inputs. But, it does appear to show the P4 being moved around in the back yard.

BudWalker Posted at 12-9 07:22
No idea why those .DATs aren’t showing up in Assistant 2. But, if you can get them from the controller please provide those. I don’t see any additional files in the GoogleDrive folder you provided in post #6.  
  FLY171.DAT doesn’t show a motor start or any stick inputs. But, it does appear to show the P4 being moved around in the back yard.[view_image]

Well thats embarassing, I copied them to  the wrong folder..  They are in the previously linked folder now.
The ones labelled Go4 are from the phone, flight 171 from the 3rd December and flight 177 from yesterday.

I havent got my head around CsvView yet, but the only thing I can see showing is motors, cant work out how to show anything else, unless that is its not there! (EDIT, the Update button at the bottom of the window was off screen..  worked it out now)

JustAskDave Posted at 12-9 13:29
Well thats embarassing, I copied them to  the wrong folder..  They are in the previously linked folder now.
The ones labelled Go4 are from the phone, flight 171 from the 3rd December and flight 177 from yesterday.

Looks to me like the ultrasonic height sensor is either malfunctioning or covered. In FLY177 the ultrasonic height is pinned close to 0.0 while the P4 achieves 6.6 meters altitude. Fly171 is similar.

  
  

The Flight Controller limits the descent speed to 0.3 m/s because it thinks the P4 is close to the ground.

fans00f1a9d8 Posted at 12-9 14:29
Looks to me like the ultrasonic height sensor is either malfunctioning or covered. In FLY177 the ultrasonic height is pinned close to 0.0 while the P4 achieves 6.6 meters altitude. Fly171 is similar.  [view_image]
  The Flight Controller limits the descent speed to 0.3 m/s because it thinks the P4 is close to the ground.

Thank you for that, I will have to have a good play with this  app as I was suspecting the Ultrasonic sensor may be the issue, also explains why randomly climbs, thinking something has come close to it.  Also Sport mode has no effect as that sensor remains active.

There is nothing blocking it, the issue started suddenly and was intermittent at first, but now all the time. I might pop the case open and see if a connection lose, but otherwise I suspect the sensors dying

Did some more testng and the VPS system is faulty    

Tried firmware downgrade to .700, no change (had seen some other reports that the update to .810 caused the problem in theirs)

Lifting the drone up you can see the VPS height increasing, then randomly it jumps back to 0.0 to 0.3 no matter what height.  Works most of the time when lifting by hand, but under its own power it fails at around 1m every time then changes to red and 0.1 to 0.3, not allowing it to descend properly.   Disabling the downward VPS fixes that issue and it flies OK after that, however of course now there is no altitude hold at low heights. Unfortunately these drones are used for training and licencing, so its no longer useful.  

I need to use Phantoms for training as the Australian Regulator (CASA) now says we need to train and assess students in Atti mode as well as GPS hold (despite there no longer being many commercially available drones with Atti mode..).   Since I can't buy anything new with Atti mode, old phantoms its is.