Two things I do not understand regarding the Phantom 4. I flew a friends Phantom 3 for a while and just bought a P4.

1. I occasionally get the error "The downward sensor is abnormal causing the aircraft to become unstable at low altitude, land as soon as possible" (but the error occurs only above 10 Meters)

I have calibrated the sensors, IMU and compass but the craft still does the same thing. Once I "ok" the message, there is no trouble but when I bring the craft back...

2. the rear status lights are solid red. After a few seconds of being under 10 meters and close to the controller, status lights go back to flashing green. I never get any errors other that the downward sensor note.

I have tried turning off the Vision Positioning which eliminates the message, but when it comes back after flight, the rear status lights are solid red, and then turn back flashing green. If I had not read the solid red lights mean critical error in the manual, I would not even worry about it. The Phantom 4 flies super and I have seen no issues with performance at all. I don't know that the two are related, they are both just happening.

Any suggestions or help would be appreciated. THANKS.

Sounds like sensor is bad.

If you just bought it then it should still be under warranty. I would start a case with DJI.

What you describe is similar to issues that have been reported across Phantom/Mavic/Spark.
Apparently that message is a bug and can be disregarded.
https://forum.dji.com/forum.php?mod=viewthread&tid=144685&page=1#pid1347729
https://forum.dji.com/thread-136473-1-1.html

I had it a couple of times and didn't care much. Since the recent Go4 update 4.2.16 it seems to ge gone.

I definitely would not send the drone in!

Eric13 Posted at 2018-5-26 09:59
What you describe is similar to issues that have been reported across Phantom/Mavic/Spark.
Apparently that message is a bug and can be disregarded.
https://forum.dji.com/forum.php?mod=viewthread&tid=144685&page=1#pid1347729

Thank you. I just checked and there is a firmware upgrade. I am downloading it now.  I hope that will fix but I’ll shout back either way!

Thanks!

Red Oak Posted at 2018-5-26 11:36
Thank you. I just checked and there is a firmware upgrade. I am downloading it now.  I hope that will fix but I’ll shout back either way!

Thanks!

Well, the firmware seemed to resolve the downward sensor error, but I still have the red status lights coming on above 10 meters. Distance does not seem to create the red light situation, but elevation over 10M will. No performance issues at all, just the lights.

Red Oak Posted at 2018-5-26 12:22
Well, the firmware seemed to resolve the downward sensor error, but I still have the red status lights coming on above 10 meters. Distance does not seem to create the red light situation, but elevation over 10M will. No performance issues at all, just the lights.

Fly with it and observe what messages you are getting.
Still I wouldn't send the drone in. That usually turns into a long term nightmare resulting in a refurbished drone being sent to you.
Start cautious, fly, get comfortable. I'm 98% sure this issue is not real.

If that issue causes your drone to crash, I'll fedex you a whole case of German beer.
You decide which brand. :-)

Eric13 Posted at 2018-5-26 12:55
Fly with it and observe what messages you are getting.
Still I wouldn't send the drone in. That usually turns into a long term nightmare resulting in a refurbished drone being send to you.
Start cautious, fly, get comfortable. I'm 98% sure this issue is not real.

LOL, ok, sounds good. Ill run with it for a while and see how it goes!

Thank you for your help.

I'm having this same issue. Don't use RTH with the rear lights solid red. My p4 came down super fast and if not for past r/c helicopter experience it would have slammed into the ground. It did not slow itself down as usual. But everything is fine below 10m. I don't get it.

Chip Cash Posted at 2018-5-26 18:34
I'm having this same issue. Don't use RTH with the rear lights solid red. My p4 came down super fast and if not for past r/c helicopter experience it would have slammed into the ground. It did not slow itself down as usual. But everything is fine below 10m. I don't get it.

Exactly... and thanks for the heads up using RTH with the red lights! I've sent a note to DJI support and I'll let ya know what they say Monday.

Thanks!

You're not using third party items as ex a gimbal/camera protector mounted on the legs right?

KedDK Posted at 2018-5-27 04:06
You're not using third party items as ex a gimbal/camera protector mounted on the legs right?

Everything is as it came from the factory.
Thanks.

Red Oak Posted at 2018-5-27 06:13
Everything is as it came from the factory.
Thanks.

okay sounds right then assuming you have found and removed all those strange sensor stickers.
Best luck for a quick solution.

Do you get the same flying in different areas, the rear lights will certainly flash red if low battery or close to a no fly zone.

The Forward, Backward, and Downward Vision Systems can be calibrated with DJI Assistant 2 and DJI GO 4. If there is an error with the Forward, Backward, or Downward Vision Systems, a prompt stating that auto calibration for the Vision System is required will pop up in the DJI GO 4 app. Follow the instructions in the DJI GO 4 app for calibration. It is recommended to calibrate the Forward, Backward, and Downward Vision Systems with DJI Assistant 2. If you don't have a computer at hand, calibrate them with the DJI GO app.

As per your second inquiry, the maximum altitude for Phantom 4 is 10m. The red light showing on the front led light on your aircraft indicates that you already reached the maximum limit.  Please refer on the specs below.

DJI Natalia Posted at 2018-5-27 07:42
The Forward, Backward, and Downward Vision Systems can be calibrated with DJI Assistant 2 and DJI GO 4. If there is an error with the Forward, Backward, or Downward Vision Systems, a prompt stating that auto calibration for the Vision System is required will pop up in the DJI GO 4 app. Follow the instructions in the DJI GO 4 app for calibration. It is recommended to calibrate the Forward, Backward, and Downward Vision Systems with DJI Assistant 2. If you don't have a computer at hand, calibrate them with the DJI GO app.

As per your second inquiry, the maximum altitude for Phantom 4 is 10m. The red light showing on the front led light on your aircraft indicates that you already reached the maximum limit.  Please refer on the specs below.

"As per your second inquiry, the maximum altitude for Phantom 4 is 10m. The red light showing on the front led light on your aircraft indicates that you already reached the maximum limit.  Please refer on the specs below."

This statement is at best incorrect. The limit of the visual positioning system is 10m above surface below. The altitude limit above take off point is 500m as set in the aircrafts firmware.

The front red LEDs are the navigation lights and are always illuminated unless you chose to extinguish them.

Aardvark Posted at 2018-5-27 06:48
Do you get the same flying in different areas, the rear lights will certainly flash red if low battery or close to a no fly zone.

Battery is good... would the air space create a solid red status light? It is not restricted but there are unmanned crop dusting strips around.

Aardvark Posted at 2018-5-27 08:42
"As per your second inquiry, the maximum altitude for Phantom 4 is 10m. The red light showing on the front led light on your aircraft indicates that you already reached the maximum limit.  Please refer on the specs below."

This statement is at best incorrect. The limit of the visual positioning system is 10m above surface below. The altitude limit above take off point is 500m as set in the aircrafts firmware.

We are speaking of the rear status lights.

Red Oak Posted at 2018-5-27 09:23
Battery is good... would the air space create a solid red status light? It is not restricted but there are unmanned crop dusting strips around.

I just had a look at manual, page 55, the rear LEDs flash red if close to or in an NFZ. But your rear LEDs are solid red (Critical error). It looks as if there is a problem with your device, best to get it replaced by retailer if new, or repaired under warranty.

Aardvark Posted at 2018-5-27 10:07
I just had a look at manual, page 55, the rear LEDs flash red if close to or in an NFZ. But your rear LEDs are solid red (Critical error). It looks as if there is a problem with your device, best to get it replaced by retailer if new, or repaired under warranty.

Yes sir, I read that too... and mine do turn solid red but then I drop back below 10 meters and they go back to flashing happy green?? I'm not quite ready to send it off and have a refurbished one sent back. There are no issues at all except for the lights.

Well I downgraded to last firmware then re updated to latest one. Re calibrated the imu and vps with assistant 2 and I am not getting that error or solid red rear lights. Only got one flight in before I started feeling sprinkled so I had to land quickly. If I get a chance any today I'll test so more to see if it really is fixed.

I did another flight once it cleared up and it's still turning solid red after about 10m but when I bring it back down the rear lights return to normal.so ut looks like I'll be sending this back since I haven't even had it a week.

Chip Cash Posted at 2018-5-28 12:15
I did another flight once it cleared up and it's still turning solid red after about 10m but when I bring it back down the rear lights return to normal.so ut looks like I'll be sending this back since I haven't even had it a week.

Exactly what mine is doing. I sent them a note and they said they did not know what it was but it was not a "critical error" or it would not come back to the flashing green. She also said if it were an error, there software should tell us. I'm going to fly a bit more and see what it does. Thanks for your input!

Jay

Chip Cash Posted at 2018-5-28 12:15
I did another flight once it cleared up and it's still turning solid red after about 10m but when I bring it back down the rear lights return to normal.so ut looks like I'll be sending this back since I haven't even had it a week.

Are you anywhere near an airport of any kind? I am a part 61 pilot as well and I am using Foreflight to determine airspace. I have been to three different locations and all of them gave me an message to fly safely due to nearby unmanned airport. (I am in the delta in Arkansas and there are crop dusting strips everywhere).

I am going to get out somewhere else and just make sure it's not something to do with "perceived" airspace issues.

I'm about 2 air miles from a small plane commercial airport but it's not a red no fly zone. Its sounds like a firmware glitch to me. I mean if it was actually failing it would alert us right after take off. Instead it's doing it after I hit a certain height when the downward sensors shouldn't even matter. But when the rear lights go solid red the downward sensors are off because of the warning, meaning RTH will not function right. I mean I could return it but Red Oak is having the exact same problem. I think it would be the same with a replacemwnt.

Same problem here with mine. All seems to be okay besides the lights. A bit annoying. Regular p4 here.

It's got to be a firmware issue. I reverted back to version .0106 and made a test flight and didn't get the error at all no matter what I did. But the old FW has too many issues to stay on it so i upgraded back to the current one. I'm going to cut off my vps and see if it still gives me the error. If it doesn't I'll just leave it off until there is a fix. Don't really need it any except for indoors or little to no GPS signal.

Did you guys find an answer to this?  I am having same problem on my Phantom 4 Pro.  Any help would be greatly appreciated.