Today I had my first and last crash of my P3P.

Im really confused as to why, as it seems there was some unusual circumstances, so there's a chance of a hardware failure.

Firstly, the P3P lost complete signal @ only 262m from my location, with 100% line of sight and a clear view of the bird from where i was controlling.

Secondly, my RTH was set @ 140m, clearly visible on the the logs below - yet is descended instead of rising with loss of signal ????

Thirdly, once RTH kicked in, my bird didnt rise, it decended as it made it's way towards me, hence clipping by inches the side of the building and crashing into an unrepairable state.

I've flown in this area heaps of times before, as it's where I live, conditons were absolutely perfect and my hardware / software 100%.

I'd really like to know why my RTH ended in a descent rather than rising.

Here's some info, if someone more experienced can look into it an give some feedback I'd be interested to see what went wrong.

Also, the crane on the google images is gone, as the development is completed now, and I was intending to take a few pics of a recently completed park.

Healthy Drones - http://healthydrones.com/main?flight=6710d49ea6338420fcd09bccc9eb428f&page_id=GENERALNotifications

	Flight time	Altitude	Home Distance	Type	Notification
A	00m 00s	0 m	0 m	Mode	[url=]Mode changed to GPS_Atti[/url]
B	00m 00s	0 m	0 m	Tip	[url=]Home Point Recorded[/url]
C	00m 02s	0 m	0 m	Mode	[url=]Mode changed to AssitedTakeoff[/url]
D	00m 02s	0 m	0 m	Tip	[url=]Return-to-Home Altitude:140M[/url]
E	00m 03s	0 m	0 m	Mode	[url=]Mode changed to GPS_Atti[/url]
F	03m 24s	57.6 m	262 m	Data Loss	[url=]Downlink data connection lost for 7.3 seconds[/url]
G	03m 24s	57.6 m	262 m	Mode	[url=]Mode changed to GoHome[/url]
H	03m 25s	58.1 m	262 m	Warning	[url=]Signal Lost. Aircraft is returning home.[/url]
I	03m 36s	26.6 m	178 m	Data Loss	[url=]Downlink data connection lost for 10.5 seconds[/url]
J	03m 36s	22.8 m	178 m	Warning	[url=]Motor Obstructed[/url]

I don't know why the aircraft descended while on RTH! Your altitude was good to clear the tall building. The only thing I would have done differently is when you lost the signal I would have stopped to see if I would regain a signal, then turned around and headed to the home point. After that point you never regained a signal. Give DJI notification and send them the flight records and see if they will replace your aircraft.

mjlstudios@yaho Posted at 2016-3-28 00:36
I don't know why the aircraft descended while on RTH! Your altitude was good to clear the tall build ...

Thanks for the feedback.

I'll be in touch with DJI for sure.

As soon as signal lost I did the obligatory hold up the controller to see if it regained  signal but no luck.

Usually you'll get some degradation in signal and an opportunity to bring it back in range / elevate etc...

I'll give DJI a shot at looking into the case, and cross my fingers.

"Im really confused as to why, as it seems there was some unusual circumstances, so there's a chance of a hardware failure.
Firstly, the P3P lost complete signal @ only 262m from my location, with 100% line of sight and a clear view of the bird from where i was controlling".

This part of the mystery is easily solved.  You flew behind the edge of a 20 storey building at 43 Shoreline Dr. (built on land that is ~7 metres higher than your home point).  Your Phantom's altitude was 58 metres.  You lost line of sight when you flew behind the edge of the building.  Thisbuilding is higher than the altitude you were flying at.

"Secondly, my RTH was set @ 140m, clearly visible on the the logs below - yet is descended instead of rising with loss of signal ????"

It's not clear why it didn't climb but what you've taken to be descending may be due to crashing into the building?

Looks like a close call to be behind that building if it was still LOS or not but the question is why didn't it climb when RTH was initiated.

labroides@yahoo Posted at 2016-3-28 01:15
"Im really confused as to why, as it seems there was some unusual circumstances, so there's a chance ...

Thanks Labroides.  

It's touch and go on your line of sight analysis.  From where i was standing my sight was pretty good.  I did use both my sight and the screen back and forth as i was in the process of adjusting the gimbal down for my shot.  

For the exercise I did take the screen shot and draw a straight line from my location (not take off point) and the point RTH kicked it. if i was well behind the building I could understand the loss of signal, but it's right on the edge and not too far away for my location so I'm still not 100% convinced there wasn't a hardware / software fault of some type.

But the point remains why it the RTH didnt ascend completely vertical as it normally the case when RTH has been utilized.

KeithS Posted at 2016-3-28 01:37
Thanks Labroides.  

It's touch and go on your line of sight analysis.  From where i was standing  ...

" if i was well behind the building I could understand the loss of signal, but it's right on the edge"

6 inches past right on the edge will do it.

It was already losing signal well before it went behind. It might of had major interference from these tall surrounding buildings.

Sorry for the loss of your bird. I agree with you, the only real question is why the RTH altitude wasn't achieved. Hopefully, DJI will find out, and replace your aircraft. Good luck.

dkruseski Posted at 2016-3-28 02:02
Sorry for the loss of your bird. I agree with you, the only real question is why the RTH altitude wa ...

Thanks - fingers crossed.  At least a lesson learnt in investigation.

I believe that it started ascending,  but you moved the throttle stick and it picked up that signal,  which immediately stopped the ascending and made your craft go home on current altitude.

kancur Posted at 2016-3-29 00:04
I believe that it started ascending,  but you moved the throttle stick and it picked up that signal, ...

I've considered that quite possibly happened.

My confusion still arises from what I read as being a drop of altitude from 57.6m to 26.6m.

Any throttle action during the loss of signal was for elevation to get signal back.   

I jut can't work out why there was a 20+m drop in height before any impact from point H to J.

Maybe it's not the exact impact time,  but a bit later when the controller assumed the motor is obstructed.  

I think thats possibly what happened.

For the RTH issue: May be a stupid sugestion!
Was the RTH/Signal lost parameter set to RTH or Hover or Land?

DJI Support will find .. and so sorry for ur Bird LOST . Mate

Don't feel bad, my P3P did the same thing friday, I pressed RTH it never got to 50m just flew straight into a tree then into a lake....

I've notice ever time I do a firmware update it resets some of my setting to default, for instants I live in the trees and I want my RTH at 50 m but it always resets back to 20 m.

Keith, Sorry man. It hurts to lose them babies.
BTW...Why do you have a picture of my wife as your Avatar?.......LOL

SHamers Posted at 2016-3-29 22:11
For the RTH issue: May be a stupid sugestion!
Was the RTH/Signal lost parameter set to RTH or Hover  ...

Hi SHamers,

Was set to RTH @ a height of 140m.

I've got this on record in the flight data.


        Flight time        Altitude        Home Distance        Type        Notification
A        00m 00s        0 m        0 m        Mode        Mode changed to GPS_Atti
B        00m 00s        0 m        0 m        Tip        Home Point Recorded
C        00m 02s        0 m        0 m        Mode        Mode changed to AssitedTakeoff
D        00m 02s        0 m        0 m        Tip        Return-to-Home Altitude:140M
E        00m 03s        0 m        0 m        Mode        Mode changed to GPS_Atti
F        03m 24s        57.6 m        262 m        Data Loss        Downlink data connection lost for 7.3 seconds
G        03m 24s        57.6 m        262 m        Mode        Mode changed to GoHome
H        03m 25s        58.1 m        262 m        Warning        Signal Lost. Aircraft is returning home.
I        03m 36s        26.6 m        178 m        Data Loss        Downlink data connection lost for 10.5 seconds
J        03m 36s        22.8 m        178 m        Warning        Motor Obstructed

mcphipps900 Posted at 2016-3-29 23:45
Keith, Sorry man. It hurts to lose them babies.
BTW...Why do you have a picture of my wife as your A ...

If that's your wife then I better wake her up and ask some questions.

True story ... she ordered me a P4 today cause she thought I was like I'd lost my best friend.

Not available for a couple of weeks here in Australia yet... now I've just got to decide if I should accept her generosity and take the P4, change it to a P3A or P3P and get her some money back, or go back to spending money on my car.

dalegeorge5 Posted at 2016-3-29 23:26
Don't feel bad, my P3P did the same thing friday, I pressed RTH it never got to 50m just flew straig ...

What have you done from here? Contacted DJI?

dalegeorge5 Posted at 2016-3-29 23:26
Don't feel bad, my P3P did the same thing friday, I pressed RTH it never got to 50m just flew straig ...

Have you learned why?
Go to http://www.phantomhelp.com/LogViewer/Upload/
Follow the instructions there to upload your flight record
Start a new thread here with a link to the report you get from that website and someone will be able to analyse it for you to see what went wrong.

This is a very interesting case.  It looks like you were flying on the edge of line-of-sight near buildings which would account for the poor signal and low GPS etc.  As labroides notes: "6 inches past right on the edge will do it."  However that didn't cause the crash.  The fascinating bit is the last track.  It is dead straight, but as you note, it is descending.  It seems to have changed heading correctly to your approximate home position after initiating a RTH.  The constant rate of descent almost seems like it is performing a land-in-place failsafe.  That doesn't explain it's forward movement though and I doubt the wind was blowing that accurately to have done it.  It would be interesting if you can play back your flight record and show your joystick inputs for that last leg and see if there is any response to your inputs, maybe a stick got stuck or you overrode the automatically set directions?

        

It is more likely that the straight line doesn't actually represent your path, rather it is joining two points where the data downlink was still working, approx 11 sec at marker "I".  For all we know it did go up, then return towards home, and fell for some other reason.  Where did you recover the wreckage, on the ground or on someones balcony?  The top of the 20 storey building would be at about 80m elevation and you were lower than that.  It's possible when the signal was lost it went into a hover, waiting for the RTH to kick in, and the wind blew it closer to the building.  Tall buildings tend to have their own micro-weather systems and the wind was likely to be turbulent close to a structure like this (I really miss the estimated wind report on the free version of Healthy Drones )  It may have been a lot closer to the building than you think.  All we can calculate from this data is that in 11 seconds, it has moved 84 metres towards the building and fallen 31.5 metres.  In the last recorded fraction of a second, it fell around 4m.  If it flew straight into the building (go-home without ascending) at 10m/s, that would leave about 2 seconds of fall, which would be about 30m.  You really need the detailed flight data from the aircraft for more accuracy and to fill in the blind spots.  I'd need to confirm that the go-home speed is 10m/s but it sounds about right, if so, these figures would confirm it has flown straight into the side of the building in the 10.5 seconds the data link was down.

That might explain what happened, but not why it did not ascend to RTH altitude.  DJI need to analyze your flight data.

Good luck!

I just realised you set the RTH altitude at 140m, but your maximum flight altitude would probably have been set at 120m or less.  I wonder what happens if a restriction conflicts with the RTH altitude?

Can the RTH altitude be set higher than the restricted altitude? If so, why?

endotherm Posted at 2016-3-30 03:29
This is a very interesting case.  It looks like you were flying on the edge of line-of-sight near bu ...

The mystery has been solved.
There was joystick input after the Phantom began RTH.
As per the manual ...
If you move the throttle after the aircraft rises above 20 m but below the preset failsafe RTH altitude, the aircraft will stop ascending and immediately return to home point.

KeithS Posted at 2016-3-29 20:54
If that's your wife then I better wake her up and ask some questions.

True story ... she ordered  ...

Choices choices choices...wish I had that dilemma...

It's in the hands of DJI now, they've replied back promptly and will look into it.

I can see that my natural reaction to push the drone upwards once signal was lost to try and regain some altitude has likely interrupted to RTH. Must have been a split second only.  

KeithS Posted at 2016-3-30 06:04
It's in the hands of DJI now, they've replied back promptly and will look into it.

I can see that m ...

I am interested in the outcome...was not aware that any input into the sticks causes RTH at the "then" height in a straight line.

Sorry for your crash, good luck.

jredford Posted at 2016-3-31 02:54
I am interested in the outcome...was not aware that any input into the sticks causes RTH at the "th ...

The manual has 3 pages of info on RTH.
Probably the most important section in the manual.
This info is halfway down page 15.
Lots of other good material in there if you read it.

jredford Posted at 2016-3-31 02:54
I am interested in the outcome...was not aware that any input into the sticks causes RTH at the "th ...

Thanks, I'll post the outcome when DJI have had a chance to respond.

I can see that in the end the blame will be most likely be given to me as a result of some members advice that the stick movement caused the crash.

But, picture this scenario, and advise how you would have reacted.

1. P3P is less than 200m from you, at a height of 58m is an area you're familiar with.
2. Signal drops out immediately and doesn't regain as it sometimes does a few seconds later.
3. You can see the drone so you press up to regain a litttle height to get some signal back.
4. The P3P show's no sign  of response - NO SIGNAL message remains on screen and the FPV view isnt regained.  RTH signal is not relayed back to the controller so you don't know what's going on.
5. You sit and wait for the drone to rise, it doesn't and then you hear the death rattle.

In a nutshell, I don't think a slight movement of a stick during a period of NO SIGNAL should initiate a stop in the drone ascending.  Especially when the signal on the screen is NO SIGNAL.

My connection to the drone might have been just a millisecond so that the stick movement was sent, bit no message on screen, no option to cancel etc.. similar to the low battery warning.

With a bit of luck my pain will be other member's gain.

And then you hear the death rattle...???
What....

Death rattle meaning the sound of a P3P hitting concrete from height.

KeithS Posted at 2016-4-2 20:31
Thanks, I'll post the outcome when DJI have had a chance to respond.

I can see that in the end th ...

The catch is that there are two signals .. one from the P3 to the controller and one from the controller to the Phantom.
You almost always lose the video from the Phantom before the Phantom loses your control signal.
This is what the msg in Healthydrones is telling you:  Downlink data connection lost for 10.5 seconds.
The uplink was still live
And that's great in most situations because it means you can fly higher or activate RTH as is appropriate.

There are a number of things that could go wrong if you want to fly behind a building,
With that much  potential for the flight to come unstuck, you can't afford to take chances.

As I anticipated the reply from DJI was pretty straight forward, something along the lines of, We repair, you pay.

Oh well.....

endotherm Posted at 2016-3-29 11:29
This is a very interesting case.  It looks like you were flying on the edge of line-of-sight near bu ...

What program did you use to display his flight like this?

I am obligated to say: Yet another crash that would have been avoided if DJI had return along path implemented rather than just Return To Home. This feature (already available in 3DR's drones) as an option will cause the drone to retrace its course a certain distance (100 meters should do the trick) which is the shortest and safest route to put the drone back into control of the pilot. Return To Home is extremely dangerous because it is autonomous flight. Buildings, trees, hills, mountains and even people can get in the way of a drone and cause crashes. Before serious injury occurs due to an unintended Return To Home, please implement return along course as a user option.
Something to ponder: What does "Return To Home" do if there is a no fly zone between the pilot and the drone? Could the drone end up flying over an active runway?

grangerfx@gmail Posted at 2016-7-8 12:17
I am obligated to say: Yet another crash that would have been avoided if DJI had return along path i ...

Do you happen to know what viewer the poster several above you used to get those graphical depictions of the OP's flight/altitude/etc?