No you didn't tell us the facts,
You told us that OA didn't work when it did,
You flew out of visual line of sight, illegally and lost signal,
You cancelled the RTH height rise but claim it malfunctioned,
You flew into an area of turbulent wind but claim zero wind,
You hide the log so that we can't confirm these facts.

People who really want help in understanding a crash give all the info they can and listen to suggestions on possible causes, you just seem to be requesting information you can use to pin the blame on DJI and get them to pay for your accident that was caused by multiple pilot errors and illegal flying.

Nigel_ Posted at 2017-4-15 23:56
No you didn't tell us the facts,
You told us that OA didn't work when it did,
You flew out of visual line of sight, illegally and lost signal,

Nigel your a plum now go report me to the police    I will break this down one last time for you .

No you didn't tell us the facts YES I DID
You told us that OA didn't work when it did, A working AO that flys in to a wall ?   
You flew out of visual line of sight, illegally and lost signal, WRONG two man team radios private land  
You cancelled the RTH height rise but claim it malfunctioned,  AGAIN WRONG check below log
You flew into an area of turbulent wind but claim zero wind, 3 ON beaufort Gentle breeze also enclosed area
You hide the log so that we can't confirm these facts. Its work related i cant share get over your self sherlock

Your wrong on all counts but thanks for proving my point about the terrible condescending and patronising attitude of some ot the people on this forum.  

Fact is the RTH altitude did malfunction its  shown below it did not set its self until i was 79 feet in the air after 7 seconds of flight. Drone was set for 80 meters height  RTH. Building is 40 meters tall . Drone  comes back at about 38  meters and give the wrong readings throughout. When faced with the building it stopped then flew left a bit and up and it mistook a different color panel for clear sky the AO should have picked up this and stopped the drone.

ENDCRASH.jpg appears to show that RTH was cancelled at 7m 12.1s. After that it was only in the air for another couple of seconds, perhaps no time for you to recover it. (Though shouldn't it just hover when RTH is cancelled, unless you are pushing the sticks?)

But, regardless of that, what seems noteworthy is the altitude. Your earlier diagram suggested that you were at 131m, and this log extract shows an altitude similar to that - 442ft. So it should have been way over the top of the building and couldn't crash in to it. Perhaps there was a barometer problem and at commencement of RTH it didn't ascend because it thought it was already above RTH altitude.

It headed home too low (and OA didn't save it because of low-light). Your argument with DJI, if any, is not about the OA but about the RTH at too low an altitude.

Not sure if it helps, but I think it might be helpful to be aware there are always going to be wind currents (you cannot feel on the ground) when flying the drone upwards into the airspace. It is even more so when flying around and in between buildings, because there are additional flows that can arise out of nowhere.

Post your logs, or STFU!

Simon Child Posted at 2017-4-16 03:33
ENDCRASH.jpg appears to show that RTH was cancelled at 7m 12.1s. After that it was only in the air for another couple of seconds, perhaps no time for you to recover it. (Though shouldn't it just hover when RTH is cancelled, unless you are pushing the sticks?)

But, regardless of that, what seems noteworthy is the altitude. Your earlier diagram suggested that you were at 131m, and this log extract shows an altitude similar to that - 442ft. So it should have been way over the top of the building and couldn't crash in to it. Perhaps there was a barometer problem and at commencement of RTH it didn't ascend because it thought it was already above RTH altitude.

Thanks for your input Simon and commodon . Yes your correct the RTH cancel registered about 2 seconds before the crash I gave no user input . Like you said I was expecting it just to remain where it was until I could get my signal back .

Regarding the wind yes your correct  you do get gusts in and around buildings but again the P4 is capable of handling far stronger winds and in my opinion was not a  factor in this crash at 40 meters altitude in this case .  

Regarding the OA and low light . The visibility was good a range of ten KM . Even at ground level is was still light and clear. What are you basing your measurement of light on ?  what is your refrence for a  definition of low light ?.

Because if what your saying is true then the  OA system would be redundant indoors with the vision Positioning  and in cloudy and overcast conditions outdoors. While I understand it may not be at optimal performance it should still function in these conditions. If this is the case DJI need to look at there user manual and advertising  video .

In my experiance i have never considered the below to be low light . Shadows can be cast at any time of the day .

I said low light because your flight was near to sunset, plus your photo above gives the impression of an overcast day - no strong shadows.

Phantom 4 vision system needs >15 lux to operate: https://www.dji.com/phantom-4/info#specs.

Wikipedia suggests 40lux at sunset on an overcast day https://en.wikipedia.org/wiki/Daylight  so you must have been near the lower limit of lighting, especially being between buildings which must cause some shading.

Indoors would be much lighter than that, with normal indoor lighting https://en.wikipedia.org/wiki/Lux  And note that it was dim enough for those inside that building to have their lights on, and these showed brighter than the light outside.

There is also the need for the surface in question to have a clear pattern, and it looks as though you crashed into a plain white panel.

But regardless - I'm no expert and not interested in an argument about light - why was it RTH at below 80m, and reporting altitude of 442ft? If it had been at 80m then it would not have needed OA, so the RTH at wrong altitude was your problem

Simon Child Posted at 2017-4-16 14:37
I said low light because your flight was near to sunset, plus your photo above gives the impression of an overcast day - no strong shadows.

Phantom 4 vision system needs >15 lux to operate: https://www.dji.com/phantom-4/info#specs.

Thanks for your break down of the light, just a debate not argument each to their own and all  . I would agree picture 1 is lowlight around 40 luxFully overcast, sunset/sunrise. But the picture of skyline i posted  showed a clear evening and the light was well over 200 lux in my opinion .

Will see if I can pick up some readings from that evening maybe i am wrong but it looked well over adequate lighting (lux>15) DJI recommends. As for a clear pattern what in the natural world has a clear pattern ? The building did have a pattern and it was clear . Difference between a clear pattern and a pattern variation is whats been mixed up here.

120,000 lux         Brightest sunlight
111,000 lux         Bright sunlight
20,000 lux         Shade illuminated by entire clear blue sky, midday
1,000 - 2,000 lux         Typical overcast day, midday
<200 lux         Extreme of darkest storm clouds, midday
400 lux         Sunrise or sunset on a clear day (ambient illumination).
40 lux         Fully overcast, sunset/sunrise
<1 lux         Extreme of darkest storm clouds, sunset/rise

Yes the RTH is what I don't understand. For some reason it set its RTH point 60 seconds in to the flight when it had a altitude of  78 feet. I think this threw it out of sync for the rest of the flight. Will speak the retailer then send it in for inspection and take it from there  nothing more to discuss until i get a diognostics , Cheers

Looks like you took off before it had acquired very many satllites and so before it had set the home point automatically - which it did once it went higher and was no longer shielded by buildings. But it still set a RTH altitude of 80m, not 78ft.

You told us that OA didn't work when it did, A working AO that flys in to a wall ?   
The obstacle avoidance stopped the aircraft before it hit the wall - the OA worked.

You flew out of visual line of sight, illegally and lost signal, WRONG two man team radios private land  
We will have to take your word for that, but normally it is very difficult to get permission from the CAA to fly dangerously, and flying out of line of sight of the pilot behind a building is dangerous because you loose radio communications and you have just demonstrated the result!  For amateurs using the FPV flight rules with an observer, the observer has to stand adjacent to the pilot specifically so that when the aircraft is about to go out of line of site of the pilot, it is also about to go out of line of sight for the observer and the observer can warn the pilot that it is about to happen and he is likely to loose control if he continues.


You cancelled the RTH height rise but claim it malfunctioned,  AGAIN WRONG check below log
There is not enough log there to show that you didn't cancel the RTH height gain, or for me to understand what has happened with the altitudes, I'm not convinced that the VPS column even matches what is in the log...
Did you not notice that your barometric altitude was showing a wildly incorrect value before you flew the aircraft into a position that required a reasonably accurate value?  Would have been sensible to check that along with your home point etc. given the nature of the flight.

You flew into an area of turbulent wind but claim zero wind,  3 ON beaufort Gentle breeze also enclosed area
Well a force 3 maybe no problem for a Phantom, but the turbulence it causes on the downwind side of a rectangular tower block can be, and to me the only sensible explanation for the instability in the last few seconds of flight is turbulence.

You hide the log so that we can't confirm these facts. Its work related i cant share get over your self sherlock
OK, but given that you have already shared some of the log, maybe you could show us the measured roll, pitch, yaw from the gyro, the x y and z speed from the accelerometer and the stick inputs for the last few seconds of flight, same time period as endcrash.jpg...   It may allow us to judge the cause of the final collision.



Your wrong on all counts but thanks for proving my point about the terrible condescending and patronising attitude of some ot the people on this forum.  

Fact is the RTH altitude did malfunction its  shown below it did not set its self until i was 79 feet in the air after 7 seconds of flight. Drone was set for 80 meters height  RTH. Building is 40 meters tall . Drone  comes back at about 38  meters and give the wrong readings throughout. When faced with the building it stopped then flew left a bit and up and it mistook a different color panel for clear sky the AO should have picked up this and stopped the drone.

I don't see any evidence of the OA failing.  Potential reasons contributing to the final collision given the information you have provided include some combination of:

Low light and poor contrast -  The OA could see the building from a distance but close up it had a view of plain concrete in low light on the shadow side of the building, the OA has a narrower FOV than the main camera.

Stick input - since it had left RTH, it is possible the sticks were moved to fly it into the wall, we haven't seen the log that would prove that false.

Poor GPS - The GPS satellite count had fallen to half, it could only see half the sky due to the building blocking the other half, that makes a good triangulation impossible so GPS accuracy would have dropped to maybe 10 meters - a poor GPS fix could easily have flown it into the building when it was attempting to hold position. You were too high for VPS to hold position, plus there was low light.

Air Turbulence - it is clear in the video that it was having difficulty maintaining it's attitude, there is even a gimbal yaw error in the log as it struggled to point the aircraft in the correct direction, this also resulted in the OA sensors pointing in the wrong direction so that it could no longer see what was in it's path.  In the final couple of seconds it appears to fall into a low pressure area that develops against the wall as a gust of wind passes by.

Other causes of the crash:

The barometric altitude looks wrong, always check the barometer before your need it to be accurate.

Pilot flying behind a building thus loosing control due to blocked radio communication.




The only aircraft problem I can see is the altitude measurements, hard to judge without full actual logs but neither column seems to have sensible data in your jpgs.  You should have checked that your home point was set before take off and checked that the barometer was giving a good value before flying into a dangerous situation.

Think we are moving in to the realm of fantasy now Nigel   . Your desperately trying to clutch on to any straw to put it down to pilot error. Fact is this, two systems did not work as intended are advertised. AO that only works once in a flight is not acceptable and the RTH altitude was no where close to the  80 meters it was set at .The wind and the light where both well within the acceptable  environmental variables set out in the user manual .

I will let you the outcome of my warranty claim . You make some good points that I will keep in mind for future. But the rest of your assumptions and your accusations of  dangerous illegal activity  that you throw around on the forums are a joke. You want to fly around big empty fields with a few daisy great I am happy for you but think about the insects .

fact is drones are used in many different environments in a safe manor and the rules are open to interpretation and until things change your best of keeping your assumptions to your self your not the drone police {:4_173:}

I rather just let this rest now , I will update it when I get some feedback from the engineers

Why does no one tell the guy what REALLY has happened? I mean the SD function?

Ok – let me do it:
The P4P has highly sophisticated on-board software.
It can detect if the pilot is conducting illegal activity - like in this case filming into apartments.
Did anyone notice the woman (in nightgown?) at the window?
Well – maybe you guys didn't but the P4P for sure did.

And it did what it is being told to do:
It triggered highly complex procedures resulting in SELF DESTRUCTION.
It completed its mission perfectly and I don't understand what all the fuss here is about.

Eric13 Posted at 2017-4-18 03:11
Why does no one tell the guy what REALLY has happened? I mean the SD function?

Ok – let me do it:

Unfortunately, Drone2621 has omitted the SD column from the log fragments that he gave us so there is no proof that your suggestion is correct.  However it may tempt him into giving us more information as previous suggestions did and thus allow us to find more genuine evidence of faults in the flight...