As usual I had a good flight with my Phantom 3 Professional last week. Got a low battery warning so I put the aircraft to the ground, smooth landing. Changed the battery for a full one and switched on again. After warming up, DJI Go told me the system was 'Ready to go'. But when trying to start the motors I got a message (in yellow) about the IMU being initialized. First I thought I had to be a bit more patient, but the situation did not change.

I decided to do an IMU calibaration. This stopped at 36% with an 'Unknown error'. I powered off and on again and restarted the IMU calibration, and now it stopped at 2%. From that moment, the app status line says 'IMU calibration required' after powering up, and calibration attemps stop at 2% every time.

Giving the aircraft a few days of rest, and cooling it (to 12 degrees Celsius) did not bring any difference, neither did updating controller, aircraft, and battery firmware.

I don't think it has anything to do with a stuck sensor. X/Y values for gyroscope and acceleration show values from -0,01 to +0,01 in rest position, and they increase/decrease when I move the aircraft.

Being desperate, I gave it a chance and tried an IMU calibration while the aircraft was positioned upside down. And gues what: this results in a 100% complete calibration! Now I was able to start the motors, but I didn't risk to fly with an aircraft calibrated upside down:-)

So I again tried calibrating with the aircraft in normal position. This resulted in an unknown error again, the first one at 22% and after that it was 2% again. This situation is reproducable:

- upside down calibration always succeeds 100%.
- then first normal positioned calibation ends at some random percentage (often 22%).
- following normal positioned calibration attempts end at 2%.

I read about Phantom 4 IMU calibration errors due to fan vibrations but I don't know if this issue relates to the Pantom 3 too. I can imagine that these vibrations have less impact at the calibration process when the aircraft is upside down, in opposition to when it is standing on its soft rubber feet.

A last notice:
Looking at 'Aircraft status/Overall status' in the DJI Go app, I see a rectangle containing the text 'Latest firmware!' followed by 'Abnormal' in red. I don't know since when this is, and if it has any relation to the calibration problems.

Does anyone have an idea what's causing this problem?

That's certainly an odd IMU reaction. Particularly calibrating it upside down.

Unless you are planning to fly inverted, not sure what to suggest.

I know what the mods will say: Send it in. ;-)



RedHotPoker

quadpilot Posted at 2017-10-1 15:06
do dji on here ever give any advice how to resolve problems
or is just a case of send it in to us

Yes, of course they offer plenty of advice... When it's a known issue.



RedHotPoker

quadpilot Posted at 2017-10-1 15:06
do dji on here ever give any advice how to resolve problems
or is just a case of send it in to us

People give advice on here all the time.  When it's not an "easy" solution (and yours is not), here's how it usually goes:

A person or two will step in and tell you to update your DJI Go 4 app, as if that has anything to do with how the aircraft flies.  Some others chime in and tell you to update your firmware.  Even though your aircraft was flying fine yesterday, and firmware doesn't just "go bad" from sitting there.

Now a moderator shows up and tells you to format your SD card.  I mean that always causes gimbal problems, right?  Nope, that didn't work.  "Update your IOS operating system" or whatever you use.  No go there, either.

And finally they just say send it in.   That's about where you're at now (if anyone at DJI would have responded by now).  Fortunately you didn't have to go through all the teeth-pulling I outlined above.

Almost never does anyone get into any real technical troubleshooting here.  Talk about accelerometer values and their eyes just gloss over.  It is unfortunate, but that's the way it is.

As for your question, I don't have any suggestions myself.  But 3 hours isn't enough time for someone else to happen to swing by who has had this exact problem before.  Give it a few days and maybe someone with an actual answer might respond.  That person will not have a DJI next to their name.  They'd probably get in trouble if they suggested opening stuff up and what not.

Some additional information:

- I just did some cautious flying in my backyard after IMU calibrating the upside down aircraft. It reacted quit normal! (no inverted flying:-). Camera operation seemed normal too. But I don't dare going above 2 meters because I know there still is something wrong...

- The 'Abnormal' message at the 'Overall status' line disappears after the  successful (but upside down) IMU calibration.

Irate Retro Posted at 2017-10-1 16:15
People give advice on here all the time.  When it's not an "easy" solution (and yours is not), here's how it usually goes:

A person or two will step in and tell you to update your DJI Go 4 app, as if that has anything to do with how the aircraft flies.  Some others chime in and tell you to update your firmware.  Even though your aircraft was flying fine yesterday, and firmware doesn't just "go bad" from sitting there.

Opening up the aircraft can result in a warranty being voided. The steps suggested are what is advised in many of these cases. Unfortunately, if we get passed that point, the person's time is considered and it does require for a technician to look at as you can only troubleshoot so much over the forum.

quadpilot Posted at 2017-10-2 14:30
hi Irate Retro
i'm not saying everyone should open the shell and dive inside
what i am saying is all i read from DJI is send it in for repair

I completely agree.  DJI should sell spares.  They should also publish technical information.  Nothing terribly proprietary, just the same info that they would give a 3rd party repair shop.

I'm as cynical as the next guy, but I don't think that DJI is making much money on repairs.  Selling brand new replacements, that's a different story.  You betcha.

Irate Retro Posted at 2017-10-1 16:15
People give advice on here all the time.  When it's not an "easy" solution (and yours is not), here's how it usually goes:

A person or two will step in and tell you to update your DJI Go 4 app, as if that has anything to do with how the aircraft flies.  Some others chime in and tell you to update your firmware.  Even though your aircraft was flying fine yesterday, and firmware doesn't just "go bad" from sitting there.

agreed...

Unfortunately this is not only the case on here but on a lot other forums. I think it's a double-sided coin; members looking for a quick easy fix which may very well not be the case and other members who are quick-fast-mcgraw to provide an answer that potentially makes for a bigger problem.

IMHO

quadpilot Posted at 2017-10-2 15:35
sorry i don't agree with the quick easy fix comment
members ask the questions because other members may of had the same problems
and the easy fix as you put it! may be able to be rectified by the end user

No problem quadpilot. Perhaps it will yield some extra views

flihi Posted at 2017-10-2 09:45
Some additional information:

- I just did some cautious flying in my backyard after IMU calibrating the upside down aircraft. It reacted quit normal! (no inverted flying:-). Camera operation seemed normal too. But I don't dare going above 2 meters because I know there still is something wrong...

Dam hadn't tried calibrating it upside down - it's working!! I'm having the exact issue, did you ever get it resolved? sounds like a fan is rubbing somewhere - wondering if that's interfering. No crashes, not sure what to think.

djiuser_XHBRl7cec2c7 Posted at 6-14 22:00
Dam hadn't tried calibrating it upside down - it's working!! I'm having the exact issue, did you ever get it resolved? sounds like a fan is rubbing somewhere - wondering if that's interfering. No crashes, not sure what to think.

To be honest I barely did any flying since then, and never had the problem properly solved. Did you do some serious flying after calibrating upside down?

I don't know exactly what you're telling about the fan. Do you mean your fan is making an abnormal sound?

Anyway it's good to hear that my 'solution' works for you too. Of course I would be very pleased if you share details in case you might find a real solution! :-)