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Some advice from P3A "old hands" please (crash report)
1271 19 2016-3-28
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Old Geezer
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Flight distance : 23691 ft
United Kingdom
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Morning all,

I had an issue with my P3A on Easter Friday as described in this Support thread - http://forum.dji.com/thread-46777-1-1.html

I know it's only Easter Monday, but I'm starting to stress a bit that I'm going to be out £700 and DJI will determine it was pilot error that caused the crash, although I can't help but feel it was electronics failure (the support thread explains why I feel that way).

Could I ask some experienced pilots to have a look at all the info I posted and give their opinion here in this thread please?

Thanks in advance

Geezer

2016-3-28
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AG0N-Gary
Captain
Flight distance : 700846 ft
United States
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After watching so many crash videos and reading explanations of what they did, I'm really beginning to suspect a chicken and egg thing.  Instead of loss of GPS causing the crash, I think something else it causing loss of control by the flight system, and the loss of GPS is caused by the bird doing so much tilting and flipping (some are upside down when they spin down) that the antenna is actually losing lock on the satellites.

Good luck with your claim.  So far, no unexplained downings with my P3A.  Just my own error, for which I replaced the affected parts.
2016-3-28
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Old Geezer
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AG0N-Gary Posted at 2016-3-28 16:03
After watching so many crash videos and reading explanations of what they did, I'm really beginning  ...

I'm tending to agree with you about the GPS Gary - the healthydrones analysis shows solid GPS reception throughout the flight (including during the tumbling descent and impact until the battery ejected immediately after impact).  

However the constant flipping between GPS and Atti mode during the descent, and the accelerometer graph shakings are as yet inexplicable to me.  Could the mode switchings be a result of the tumbling or the cause of it?  Are the accelerometer fluctuations the aircraft trying to recover stable attitude or the cause of falling out of the sky?  If either (or both) are the cause of the crash, what caused them to occur?

I'm still very much perplexed about the massive compass interference (reported by the healthydrones analysis) that initiated the fall from flight and the tumbling/shaking/motor speed variations that followed.  You can see from the flight path overlaid on the screenshot of the beach that there were no obstacles or interference sources anywhere near or between the RC and aircraft.

Hoping DJI Support can shed some light on it.
2016-3-28
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Kneepuck
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Just log  at thes,,e thing that would explain all the symptoms would be a bird strike.  Did you notice any birds flying where you were?  The switching between gps and atti could be from the drones tumbling.  Same could be true of compass anomalies.  Spinning the drone in flight can screw up calibration.  Tumbling would,  I imagine,  do the same.

2016-3-28
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Old Geezer
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Kneepuck Posted at 2016-3-28 20:47
Just log  at thes,,e thing that would explain all the symptoms would be a bird strike.  Did you noti ...

Funnily enough I had the same thought at the heart stopping moment when I saw the aircraft start tumbling ... but there were no birds visible anywhere on the beach or waters edge.  Nor had there been during the immediately previous flight (none recorded on the video taken during that flight either).  

If it were something as simple as that, it would have registered with me and I'd be on the phone to Drone Doctor requesting a paid-for repair this morning.

Still baffled ... and have a strange feeling of emptiness similar to when a loved one passes away.
2016-3-29
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showardsh1967
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Hello Geezer, Sorry to here about your P3A. I am a newbe 2 the dji family here, i had a flyaway with a different drone lets just say it was suppose to get 30min. flight time. kinda reminded me of my dog getting off my lease u might get it back. I did look at your flight log and i have now the same P3A as you. one thing did catch my eye was before you took off to fly did the rc an anyway suggest that there was a update for P3A also wind speed was 11mph to 18mph. Now i no a littel bit more about this hobbey , I think i lost my bird flying it to close to cell tower and windy day 25mph with gusts to 45mph. it was stupid of me to fly in that condition. Still have not found my old bird yet but my P3A is now set up with trackimo. had this new one for 2 months an yet to fly to weather conditions are right an for me to get more experince
2016-3-29
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CapitAn
First Officer
Canada
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Old Geezer Posted at 2016-3-29 04:56
Funnily enough I had the same thought at the heart stopping moment when I saw the aircraft start t ...

l'm sorry about your crash.
l can't think of anything that can help understand what happened. The loss of GPS and going into Atti mode is indicative of it spinning and could have happened after the "event" rather than being part of the cause.

The other thing you asked about from the first flight - flipping from Follow to FPV - check to see what your C1 and C2 button defaults are. lt looks like you pressed one accidentally during flight. lt happens.
2016-3-29
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labroides
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Old Geezer Posted at 2016-3-29 19:56
Funnily enough I had the same thought at the heart stopping moment when I saw the aircraft start t ...


Looking at your two threads on this incident ...  I can't tell you why your Phantom fell from the sky, perhaps DJI will have better luck looking at the full record stored in the Phantom.
I can help point out a few red herrings that aren't relevant though.

"I'm a little suspicious that it suffered some sort of failure to the GPS unit"

A total failure of the GPS won't cause a Phantom to fall from the sky.  It would simply hover or fly without the benefit of horizontal position holding.

"Take off at 17.29m GPS & Barometer - - but actual was only 2 metres above mean high water line ... does this mean the GPS and barometer were faulty?"

There is nothing to indicate a fault in either GPS or barometer.  Because GPS is useless for accurate altitude data, the Phantom ignores any altitude reported by the GPS.  The barometer has no idea of sea level and only records altitude relative to the launch point which is zero.

"During the same period, the GPS satellite count held steady at 18 satellites with a momentary dip to 16, however there was an increasing difference between the reported height by GPS and Barometer ... could the barometer have been skewed by flying in and out of cloud shadows. as well as over sand and water - air temperature and density changes?"

Flying through cloud shadows or flying over sand and water would have no impact on altitude accuracy.  As mentioned above, the Phantom doesn't look at GPS altitude so the difference you noted is irrelevant.  GPS altitude fluctuates and this is probably the explanation.

"From 03:48mins until impact at 03:55mins, there was sudden and massive compass "interference" according to exmaps.com's extraction from the .DAT file - did the compass unit fail?"

A compass sensor doesn't usually fail and if it did, your Phantom would not fall from the sky.  What you are asking about is simply the compass recording the spin as it falls.  The compass did not fail.
2016-3-29
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Old Geezer
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Thanks CapitAn - it's always possible I suppose, and I know I have pressed the C1 by accident sometimes when picking up the remote (I have a slight paralysis in my left little finger and it sometimes does things I don't tell it to do, which is why I normally keep it well out of the way when flying).

Labroides - thanks for the detailed and informative reply ... it's somewhat comforting, but adds to my perplexity regarding what happened to cause the fall.

---

On a related topic - the dealer (Quadcopters UK) has sent me an RMA number for return and analysis (and onward return to DJI for warranty repair if applicable and needed) - is this the normal route for UK buyers?  

I also have a ticket in with DJI EU but have only received the auto reply so far from them.  I don't want to queer the pitch with the dealer by holding out for weeks for a DJI RMA number, and don't want to upset DJI by sending it through the dealer if that's the "wrong" way to go.  At the same time, I do want it fully checked and repaired to "as new" condition and status.  Does anyone know if this is what can be done at the named dealer?  Does anyone know if they are a DJI approved service centre?

As you can probably guess, I'm getting a little paranoid and concerned about the airworthiness of the drone when it comes back.

Thanks in advance
Geezer
2016-3-29
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Old Geezer
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Quick update to note that DJI-EU in Holland sent me the Analysis form to complete yesterday afternoon.  Completed and returned it within a couple of hours after information gathering (logs had already been synched to the cloud).

Fingers crossed for a speedy decision from them so I can get the repairs done a.s.a.p. - the weather today is perfect flying weather
2016-3-31
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Old Geezer
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Update (copied from my post in the support thread) -

After taking a week to analyse the flight logs, and DJI-Ken's kind intervention, an RMA number and return collection was organised.  UPS uplifted the box on Monday this week and their online tracking system shows it was delivered to DJI Holland today at 1:36pm, signed for by "Been".

Hopefully they'll repair and return it quite quickly now ... fingers crossed as it's taken 4 weeks to get to this point.

DJI-Ken or others ... will this lost month of use be added to the end of the warranty period?  Just a thought.

Geezer
2016-4-20
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Homestead72
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Old Geezer Posted at 2016-4-20 14:59
Update (copied from my post in the support thread) -

After taking a week to analyse the flight logs ...

Hi Geezer,

Did they tell you what they found after analysing the logs?  
2016-4-28
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edcarold
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Canada
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It looks like it had a collision in the air with something like a bird.
2016-4-28
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Old Geezer
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Homestead72 Posted at 2016-4-28 19:49
Hi Geezer,

Did they tell you what they found after analysing the logs?

The only "admission" they made was that the return and repair would be free of charge due to a "quality issue".

According to the repair tracking system it has been repaired and waiting for despatch for the last 3 days - wish they'd get a move on, it's a holiday weekend this weekend in the UK and lots of stuff happening that I could have been out filming (weather permitting).

Geezer
2016-4-29
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Old Geezer
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Flight distance : 23691 ft
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edcarold Posted at 2016-4-29 02:45
It looks like it had a collision in the air with something like a bird.

I can understand why you say that, but the only bird in the air on the whole beach was my P3A.
2016-4-29
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Old Geezer
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Flight distance : 23691 ft
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Old Geezer Posted at 2016-4-29 15:04
The only "admission" they made was that the return and repair would be free of charge due to a "qu ...

LOL

10 minutes after the above post, the status was updated to "despatched", and 10 minutes after that I got the tracking email from UPS

... now that's action!

It'll still not be here for another 5 days (according to UPS), but at least I know it's on it's way.

Wonder if it'll be the only drone with more time in the air as a passenger in a courier's aircraft than under its own power?
2016-4-29
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nigelw
First Officer
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Old Geezer Posted at 2016-3-29 17:15
I have a slight paralysis in my left little finger and it sometimes does things I don't tell it to do...

I think I have the same problem with my middle finger.  It gets me into a lot of trouble sometimes.
2016-4-29
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Old Geezer
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nigelw Posted at 2016-4-29 17:19
I think I have the same problem with my middle finger.  It gets me into a lot of trouble sometimes. ...

LOL Nigel - I have that problem on my right hand but the doctor says he can't fix it
2016-4-29
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Homestead72
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Old Geezer Posted at 2016-4-29 15:04
The only "admission" they made was that the return and repair would be free of charge due to a "qu ...

Glad to hear you will be flying again soon.  Shame you didn't get it sorted for the bank holiday though.

Just out of interest , did DJI charge you for the shipping for returning the drone?
2016-4-30
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Old Geezer
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Flight distance : 23691 ft
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Homestead72 Posted at 2016-4-30 19:33
Glad to hear you will be flying again soon.  Shame you didn't get it sorted for the bank holiday t ...

No, no mention has been made of me having to pay for anything.
2016-5-1
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