I just took out my shiny new P4 for a flight. It worked like a beauty -- It was windy (20-25 mph winds) and I was very worried that it would be unstable, but the stability of this craft is incredible.

I was tempted to test it, and I tested the obstacle avoidance by driving the drone to myself or towards my wife :-) -- and the bird stopped on its tracks without a problem. I then let it ascend pretty high and took it out far. Then, once it was far out, I invoked RTH from the DJI Go App. On the video monitor, I noticed that the drone turned around and started returning at pretty high speed (it could have been bolstered by heavy winds), but intermittently I noticed a yellow "Forward Obstacle Sensing Not Working" error as it was returning to home. I freaked out, but because my RTH height was adequately set, I suppose, it never ran into any obstacles and came back home safely.

Has anyone else noticed this problem? Is this is a result of the wind (probably additional tailwind causing the drone to go faster on return), or something unique to my unit? When I tested obstacle avoidance, it seems like it works, and I'm still unclear why it gave me this error (it happened twice when traveling afar and returning home).

I received this same warning yesterday, when I was flying my P4 at ~200FT in the air, with some winds. It gave me that warning during RTH. I'm not sure what triggered it either, but I was worried. Hopefully someone has an answer to this
UPDATE
I did fly above power lines, that may have caused some interference (see thread: http://forum.dji.com/thread-4272-1-1.html), but I'm not sure. Can anyone confirm?

Did you run DJI Assistant and properly calibrated the obstacle avoidance cameras before flight?

ArcticM39 Posted at 2016-4-5 17:18
Did you run DJI Assistant and properly calibrated the obstacle avoidance cameras before flight?

i've probably read every thread on this forum and watched every video DJI made about the P4, read the manual (all 65 pages) twice, and nowhere has it been mentioned that you have to calibrate the obstacle avoidance cameras before flying. If this is true, please provide a link/source where you got this information from or, even better, a screenshot of this process you speak of. Thanks.

I very well could have been the angle of the aircraft as it cannot be tilted too much for the obstacle sensing system to work. And you did have it enabled for that part of the flight correct?

FatedFilmsNC Posted at 2016-4-7 01:36
i've probably read every thread on this forum and watched every video DJI made about the P4, read t ...

Those would only require calibrating if there's an issue and it would probably give you a warning that the cameras need to be calibrated.
If you experience issues with the obstacle avoidance then a calibration wouldn't hurt. BUT I don't think the OP had that problem.

DJI-Ken Posted at 2016-4-6 13:51
Those would only require calibrating if there's an issue and it would probably give you a warning  ...

what's the SOP for calibrating the obstacle avoidance cameras? Just in case I have an issue in the future.

FatedFilmsNC Posted at 2016-4-6 10:36
i've probably read every thread on this forum and watched every video DJI made about the P4, read t ...

Guess I worded that poorly. I meant if the user has a problem with the obstacle avoidance system, then it may be prudent to re-calibrate before flight. Page 21 of manual.

FatedFilmsNC Posted at 2016-4-7 02:33
what's the SOP for calibrating the obstacle avoidance cameras? Just in case I have an issue in the  ...

SOP is calibrating cameras if there's been hard impact.

ArcticM39 Posted at 2016-4-7 02:36
Guess I worded that poorly. I meant if the user has a problem with the obstacle avoidance system,  ...

Correct, image from page 21 posted.

DJI-Ken Posted at 2016-4-6 19:49
I very well could have been the angle of the aircraft as it cannot be tilted too much for the obstac ...

The speed maybe but the angle with a tailwind ? I think you're wrong

Ulysse Posted at 2016-4-7 03:28
The speed maybe but the angle with a tailwind ? I think you're wrong

That was headwind, I just saw that OP said it was a tailwind. So the angle wouldn't change much with a tailwind.

Hi,

I have literally just experienced the same issue with the "forward Obstacle Sensing Not Working" alert on my brand new phantom 4.

The obstacle sensors were absolutely fine on a low altitude test but when flying at an altitude of 80m with RTH active I got the alert, I tested it again on the 2nd flight in the same location and got the same message.... did anyone get to the bottom of this? Do I need to return the drone?

Thanks,

Scutterx Posted at 2017-1-11 07:45
Hi,

I have literally just experienced the same issue with the "forward Obstacle Sensing Not Working" alert on my brand new phantom 4.

I would try calibrating the sensors first using DJI Assistant 2 on a PC, connected to aircraft via USB.

Also check and make sure cameras are clean.

What time were you flying , Obstacle Avoidance will not work if it's starting to get dark.


Video below gives an indication of how it should be done, latest version of assistant 2 is slightly different in visual appearance.

Aardvark Posted at 2017-1-11 07:50
I would try calibrating the sensors first using DJI Assistant 2 on a PC, connected to aircraft via USB.

Also check and make sure cameras are clean.

Thank you for your reply, the Phantom 4 was literally brand new and out of the box. I haven't tried the calibration just yet, there was a slight wind and it was a little cloudy.

I was just a bit worried as 'Forward Obstacle Avoidance not working' suggests something is wrong rather than 'not available' if that makes sense?

Scutterx Posted at 2017-1-11 07:55
Thank you for your reply, the Phantom 4 was literally brand new and out of the box. I haven't tried the calibration just yet, there was a slight wind and it was a little cloudy.

I was just a bit worried as 'Forward Obstacle Avoidance not working' suggests something is wrong rather than 'not available' if that makes sense?

Check that Obstacle Avoidance is activated in 'Visual Navigations Settings' menu. (with device, RC & aircraft all connected and powered up, with no props fitted for safety).

Scutterx Posted at 2017-1-11 07:55
Thank you for your reply, the Phantom 4 was literally brand new and out of the box. I haven't tried the calibration just yet, there was a slight wind and it was a little cloudy.

I was just a bit worried as 'Forward Obstacle Avoidance not working' suggests something is wrong rather than 'not available' if that makes sense?

As it's new to you I would suggest you download and read the manual cover to cover at least a couple of times before flying, especially the section on RTH.

Aardvark Posted at 2017-1-11 08:02
Check that Obstacle Avoidance is activated in 'Visual Navigations Settings' menu. (with device, RC & aircraft all connected and powered up, with no props fitted for safety).

Hi, yes it's all activated, worked fine when it was at a low altitude and the warning only ever appeared when it was set to RTH.

Scutterx Posted at 2017-1-11 08:03
Hi, yes it's all activated, worked fine when it was at a low altitude and the warning only ever appeared when it was set to RTH.

Also , don't rely on RTH it is not totally failsafe, best if you can fly it home yourself.

Aardvark Posted at 2017-1-11 08:05
Also , don't rely on RTH it is not totally failsafe, best if you can fly it home yourself.

That's good to know :-) do you think it is worth returning it or would you put it down to a glitch?

Scutterx Posted at 2017-1-11 08:07
That's good to know :-) do you think it is worth returning it or would you put it down to a glitch?

Try the sensor calibration first and see how it performs. It 'may' just have been a glitch, but worth keeping an eye on. If bought locally then the no quibble returns are 2-4 weeks depending on supplier.

I would do a quick run through all the calibrations Sensors(Assistant 2), IMU(on a level surface), Gimbal (right after IMU), RC sticks (with aircraft off) and finally Compass (in an open area, no ferrous materials close to aircraft. i.e. Cars, Rebar in concrete, Big steel structured buildings etc...).

I think you can get that message if it can't seen anything clearly, and the higher you are the more difficult it is to see features in what is ahead, especially if most of the image is clouds, also it can have difficulty seeing if it is flying into the sun and at this time of year in the UK it may not be really bright enough for the tiny cameras even at mid day!

If it is working at low level when there are actually things in front of it then I wouldn't worry as long as it is actually turned on.  Don't ever fly assuming that it will see things and avoid them, it has avoided a lot of accidents and is definitely worth having but it can be blinded by the sun and it doesn't work after sunset - use it like a car airbag, it may save the drones life one day but don't put peoples lives at risk unnecessarily by flying towards them!

Thank you Nigel, that gives me some peace of mind I was genuinely worried that this was a fault. It just doesn't explain why the warning did not appear whilst I was in control but the moment I hit RTH it starting complaining., unless it could have been the speed+wind+cloud as i've noticed RTH seems to fly much faster than manually controlling the P4.

I have seen this too while flying into the sun.. Just the sensors being blinded by the sun..

Since forward sensors worked (

Since the forward avoidance worked I assume you were set to p mode. Upon returning, if the speed exceeds the sensor max speed, the front sensors will be disabled automatically ( the range is cancelled by speed meaning the drone won't be able to stop effectively from excessive speed). Now RTH requires a safe altitude, above land features, where the drone can fly close to max speed. I always fly in p mode where sensors are enabled, but keep the altitude at 30m to make sure she has no obstacles in her path.