P4 cannot return home and LOST after upgrade
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3949 89 2016-5-29
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chbrian.cheung
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Hi,

  Just did an upgrade of firmware today and tried to hover around. After finished a flight, I took it off again and it was just a few hundreds feet away. With about 42% of battery left, I initiated return-to-home but after that, aircraft disconnected. And then it never came back.....

  While flight log says good GPS signals throughout the flight, battery temperature went up over 120F. Not sure if that was a battery problem or interference. But it just totally disappeared all of a sudden. Sent email to DJI and waiting for a reply...

Flight logs:

First flight after upgrading:
  http://www.phantomhelp.com/LogViewer/HTV1EM3MC4PQCBNDY1C5/
  http://healthydrones.com/main?share=aiFRxt
Last flight:
  http://www.phantomhelp.com/LogViewer/LOKWIISIG0EMH7C92X10/#
  http://healthydrones.com/main?share=jXrrHD
2016-5-29
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labroides
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Your flight records look perfectly normal and don't give any clues as to what might have happened.
Unfortunately the record just ends 4 seconds after RTH was initiated and RTH appears to have been working normally for the 4 seconds we can see.
WHatever the problem was, it happened after this.
The altitude appears to be sufficient to clear the buildings you flew over half way.
What is the height of any of the high buildings around the end of the flight record?

2016-5-29
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chbrian.cheung
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On its way to home, there is no tall buildings, but only small houses (i guess they wont be any higher than 100 feet)..
2016-5-29
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labroides
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It started to RTH and should have come home.
Unfortunately we only have flight data for 4 seconds after RTH commenced so the flight record doesn't help understand what went wrong.
Is this definitely the last flight record for that day?
2016-5-29
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chbrian.cheung
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Yes, I am sure about that. Is it possible that DJI would replace with a new one? It was a software error...
2016-5-29
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labroides
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chbrian.cheung@ Posted at 2016-5-30 00:14
Yes, I am sure about that. Is it possible that DJI would replace with a new one? It was a software e ...

Unless you can prove it was a software error I don't think you will have any luck.
And there's nothing in your flight record that gives any clue that there was any kind of error.
Why do you say it was caused by a software error?
2016-5-29
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leanlinao
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chbrian.cheung@ Posted at 2016-5-29 21:39
On its way to home, there is no tall buildings, but only small houses (i guess they wont be any high ...

30m or 100 feet is a bit too low, there can still be obstacles at that height in small house areas especially when you don't know the topography of the land and it can go up or down.

If you have a complete disappearance of the p4 after 4 seconds of rth

Most likely that means your aircraft hit something and the battery came off due to the initial collision.

Why didn't you go to the drones' last location?
2016-5-29
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leanlinao
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Or maybe someone shot your drone and that usually knocks out the battery.

If you went to it's final location on the map, it should be around there but someone could have cleared the debris already if it is far.
2016-5-29
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labroides
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leanlinao Posted at 2016-5-30 00:49
30m or 100 feet is a bit too low, there can still be obstacles at that height in small house areas ...

The Phantom was 423 feet up and in RTH when the flight record ends - not 100 feet.
People shooting a Phantom out  of the sky in Hong Kong sounds pretty unlikely.
Hong Kong isn't the wild west.
2016-5-29
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chbrian.cheung
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The RC was disconnected after RTH was initiated, so the record wasn't sent to the RC. And therefore, I think it was still returning home. I just doubt that the battery temperature was the cause. As it went beyond 120F at the end of the log and (maybe) there was a power cut. I'm just guessing around..
2016-5-29
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leanlinao
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labroides@yahoo Posted at 2016-5-29 23:11
The Phantom was 423 feet up and in RTH when the flight record ends - not 100 feet.
People shooting ...

Oh haha then I guess your p4 must have returned not home but elsewhere. Gps and compass error maybe?
2016-5-29
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labroides
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leanlinao Posted at 2016-5-30 04:04
Oh haha then I guess your p4 must have returned not home but elsewhere. Gps and compass error mayb ...

You're just making crazy guesses without even looking at the flight data.
The compass and GPS were fine
2016-5-29
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leanlinao
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labroides@yahoo Posted at 2016-5-30 07:02
You're just making crazy guesses without even looking at the flight data.
The compass and GPS were ...

So where did it go to? Did you even bother checking the final location and the route towards homepoint.
2016-5-29
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Alari
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Switzerland
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It would help if you had found pieces of it anywhere between the 2 points.
What Dji will ask you to do anyway is to sync your original flight logs from the app, so they can analyse the flight themselves, but without recovering the aircraft your chances for a replacement are unfortunately very slim..
Even though it seems that your altitude for the area was sufficient. What you could also do, is upload the last video you have stored on your app from the flight if any..
I always record as much as possible, even on returns and discard the footage I don't need (just in case) I've also never dared to use the RTH from all the horror stories I read here and rather just fly it back myself manually (and it's more fun also)
2016-5-29
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labroides
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Alari Posted at 2016-5-30 15:30
It would help if you had found pieces of it anywhere between the 2 points.
What Dji will ask you to  ...

" I've also never dared to use the RTH from all the horror stories I read here and rather just fly it back myself manually"

RTH horror stories are usually from people that have never tried RTH and don't know how it works.
The day you need RTH is not the time to start learning about it.
2016-5-29
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DJI-Paladin
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Sorry for your loss,Cheung. Actually the firmware has nothing to do with the fly-away issue.Could you leave me your ticket number here? Thank you.
2016-5-29
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markaguille
Second Officer
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Take a look at the area on Google Earth. My guess is it's stuck up a tree right next to the small, 30 storey house. Approximately 250m from where you took off, take a walk across Sha Tin Rd, as you turn left into Shui Chuen Au St you will see sky scrapers to either side of you and a high bank on your left with lots of tall trees, have look in these trees.

I think you will have better luck here than down the software error path.
2016-5-29
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SajidShah
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Sorry for ur lost
2016-5-29
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leanlinao
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markaguille Posted at 2016-5-30 15:21
Take a look at the area on Google Earth. My guess is it's stuck up a tree right next to the small, 3 ...

The guy should have searched in between the final point and the home point.
2016-5-30
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leanlinao
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Also you were on a highway and the land from there is higher, highway poles are usually high. My guess could only be you hit something like a pole and that knocked off the battery.. still you should have searched for it.
2016-5-30
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leanlinao
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You had final location data, the most valuable information to find your drone. Although there was a chance of it getting stolen, still it looks like you just sit there and waited for nothing.
2016-5-30
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labroides
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leanlinao Posted at 2016-5-30 22:45
Also you were on a highway and the land from there is higher, highway poles are usually high. My gue ...

You really need to look at the  data before you make guesses like that.
There is only a few metres difference in land elevation between start and end of the flight record.
It's near flat and the  Phantom was up 423 feet!
Power poles aren't going to be involved - they don't make them that high.
2016-5-30
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leanlinao
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labroides@yahoo Posted at 2016-5-30 20:52
You really need to look at the  data before you make guesses like that.
There is only a few metres ...

It's not a guess anymore. I looked at the visuals from the satelite and the highway which is going up alone is a good 100m high excluding the pole.

Your drone definitely hit a highway pole and I'm afraid you did not bother running and picking it up. Phantoms are very durable and that would have been repairable. Sorry it's your mistake to make the wrong calculation and also it's another not to go find it.
2016-5-30
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leanlinao
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Likely it was the pole or the wires of the pole which are pretty tough and when you hit them that can loosen or knock out the battery.

Don't take this the wrong way but there's no other reason because your final location is on a highway bridge going up and it had poles which the satelite visual showed.
You hit RTH and it took only 4 seconds. It is definitely a collision.

You made 2 mistakes
Wrong calculation
And
You did not go and pick it up.
2016-5-30
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leanlinao
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labroides@yahoo Posted at 2016-5-31 00:10
I don't know what you are looking at but it's not where he lost his Phantom.
The main road he flew ...

That bridge is high, it even has a road under it.
2016-5-30
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leanlinao
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Infact it's higher than the 7 story building beside it.
2016-5-30
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labroides
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leanlinao Posted at 2016-5-31 02:07
Likely it was the pole or the wires of the pole which are pretty tough and when you hit them that ca ...

What's the GPS location of this pole that you can see?
2016-5-30
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Alari
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labroides@yahoo Posted at 2016-5-30 07:48
" I've also never dared to use the RTH from all the horror stories I read here and rather just fly ...

I know exactly how RTH works and what is the result of it depending the drones distance from the homepoint, all different ways to cancel it and how to still have control over the aircraft during. I was very excited waiting for my drone to arrive, so I did a lot of manuals and other materials reading (It's just how I am, when excitedly expecting my new toys to arrive)

I also managed to learn how to fly the craft from the very first minute I took it off. It was my first drone ever and no, I didn't go crazy, I just checked if I know what I'm doing in simulator tested controls while hovering low, it was all pretty straight forward, did the first few flights only in beginner mode and was confident enough to switch it to expert the next day. Have been flying as often as possible for a month now. Of course My physics and engineering background may have helped a little..

What I'm trying to say I don't appreciate being presumed incompetent, It's just my preference not to use the RTH when not necessary, because I like to have more control over the drone and situations in general. And based on the horror stories I read and hear of RTH being the cause of flyaway, I feel that not relying on it is justified.
2016-5-30
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chbrian.cheung
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@Alari RTH was initiated by the disconnection between RC and the aircraft.
Not trying to justify myself or whatever here,
With the data provided by the flight log, the last known location was 22.37440219N        114.1959707E

So, I have done a bit of physics here.
Considering the last few data that the log provided. It indicated that the aircraft had no change in yaw (so we could reasonably assume that its direction was pointing to home)
If it kept heading back to home, that is, RTH working normally, it should not have hit the pole. (Moreover, fyi, the altitude of the highway was even lower than the home point. And a typical pole has an height of less than 6 meters in Hong Kong. Note that the altitude above home point was 128.9m, way higher)

Assume that it got hit by a fast moving object (to be reasonable, say, a bird) and the battery came out, the drone lost its power immediately, with a horizontal velocity Vx = 1.7ms-1 and vertical velocity Vy = 0.
So we are now considering a projectile motion, (Autorotation is neglected for the sake of calculation and with the relatively heavy drone body when compared to the light and thin propellers, autorotation would not take any significant role here.)
Vertical motion:
By s = ut+1/2 at^2      ........ air resistance will be neglected as the drone has an aerodynamically favourable shell and heavy body.
    (128.9+31.55) = 0 + 1/2 (9.81) t^2       ........ 31.55m was added to the equation to get the maximum range of motion when we later calculate the horizontal distance that it could travel.
    t = 5.72s
Horizontal motion:
    v = u +at
    v = u    ....... again, a = 0 as the air resistance in the x-direction was neglected to deliberately overestimate the range of horizontal motion.
So for the 5.72s, it could have travelled 5.72*1.7 = 9.72m ~10m
Look at the map again, for this distance, it would have dropped onto the highway if it travelled along its initial direction. Yes, @leanlinao. After doing some real calculations it should be on the highway. And you may want to check the exact location based on the evidence provided by the GPS.
But after driving out to the highway immediately, nothing was found.
So if RTH was working normally, it should have been on the highway.
2016-5-30
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labroides
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Alari Posted at 2016-5-31 02:47
I know exactly how RTH works and what is the result of it depending the drones distance from the h ...

"And based on the horror stories I read and hear of RTH being the cause of flyaway, I feel that not relying on it is justified."

Most "horror" stories" are due to user error and misunderstanding.
I haven't read any incident reports that showed a problem with RTH, but plenty where the problem was the operator's lack of understanding.
RTH is very reliable but if you don't know how it works and how to initiate it, it's just another thing to misunderstand and make mistakes with.

I've read several "horror stories" of people that lost their Phantoms simply because they didn't even know how to properly push the button to activate RTH.  
2016-5-30
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Phantomski
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Agreed, the RTH horror stories rarely seem substantiated, but I know there are some special options in the app to enable in China... not sure why and how they work.. but could that be enough where you see the last point here, but it's actually a significant number of feet away from the mapped point? Also keep in mind, that online maps are not olways on par with GPS coordinates for every location.. there's a lot of streaching and compressing required to make layers and sections fit together...  If you have the ACTUAL coordinates, can you use your phone to go to these specific coordinates and investigate?
I know, this is not the most comforting thing overall.. but if you want to try another recovery, maybe this way of thinking will help a bit.. or not.. If you do recover the aircraft, the actual logs from it can be extracted, most likely, and DJI may be able to figure out what happened and why... worth a try!
Good Luck on this! I can only imagine the pain of dealing with this!
2016-5-30
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soundbyte58
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labroides@yahoo Posted at 2016-5-30 16:50
"And based on the horror stories I read and hear of RTH being the cause of flyaway, I feel that not ...

One of the most common user errors is failing to confirm an updated home point, before lifting off. However, according to the log, it was within feet of the take-off point. According to the data, the craft was hovering on heading 195 when RTH was initiated. It immediately went full left rudder and started accelerating on heading 42. However it only got up to walking speed before it went dark. It seems to me, judging by the abruptness of the lost data link, that the battery may not have been seated properly. The P4 can be powered up with the battery still unsecured by the clips, at least mine can. The battery simply vibrated loose. RTH was initiated buy the PIC and was functioning as it should, the attitude data confirms this. I've plugged the KML file into google earth where you can see the flight path in 3D, not just top down. It should be on the road but someone could have grabbed it easy enough. It definitly didnt hit a pole, thats just pure conjecture.
2016-5-30
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leanlinao
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You successfuly initiated return to home and after 4 seconds, suddenly your drone magically disappears?
No. Your drone most likely hit something and knocked out the battery. Don't rely on obstacle avoidance because it can't see power lines or it can get stuck returning home.

The biggest mistake you made is you did not hustle to go and get your drone. Too bad for you.
2016-6-4
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labroides
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leanlinao Posted at 2016-6-4 18:52
You successfuly initiated return to home and after 4 seconds, suddenly your drone magically disappea ...

What could he have hit at the level he was flying?
What happened to your invisible pole?
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leanlinao
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labroides@yahoo Posted at 2016-6-4 16:53
What could he have hit at the level he was flying?
What happened to your invisible pole?

You need to go take a walk out there and look for it. There are many poles on the highway in the picture and even a signboard.


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leanlinao
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You also talked about 400 feet, well the land and highway + obstacles can be that high or higher.

Like I said you made 2 mistakes wrong calculation and no hustle. Too bad for you.
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labroides
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leanlinao Posted at 2016-6-4 19:07
You also talked about 400 feet, well the land and highway + obstacles can be that high or higher.

...

Can't you read at all?
It's  not my Phantom.
I live thousands of kilometres away.

And as has been mentioned by several posters above, you're idea of heights in that area is very, very wrong.
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leanlinao
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labroides@yahoo Posted at 2016-6-4 17:11
Can't you read at all?
It's  not my Phantom.
I live thousands of kilometres away.

When your phantom cracks, don't cry okay?
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labroides
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leanlinao Posted at 2016-6-4 19:16
When your phantom cracks, don't cry okay?

Sure ... you get everything else completely wrong and expect me to believe that you have a magical knowledge that my Phantom will crack up.

You're cracking me up.
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leanlinao
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labroides@yahoo Posted at 2016-6-4 17:27
Sure ... you get everything else completely wrong and expect me to believe that you have a magical ...

It's not magic lol just physics

Too bad for you.
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