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FailSafe RTH - coordination - crash [+ LOG]
797 13 2017-6-26
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Xavier1984
First Officer
Flight distance : 641171 ft
Switzerland
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[Phantom 4 Pro - Ipad Air 2 - DJI Go 4 - Last firmware on drone, RC, application]

Hi,
I have some questions about the failsafe RTH process :

- Firstly, the failsafe RTH initialize itsel automatically only when the RC SIGNAL is lost and not when the VIDEO SIGNAL is lost. Is it right ?
So, if i lose the video signal only, i can continue to pilot the drone, and the drone react to the command.

- If i lose the rc signal, the drone stop to move and hover immediatly: is it right ?
After 3 seconds, it launchs the failsafe RTH. go to the rth alltitude (60 meters for my settings), lock GPS signal and go home. The drone must be in a bigger radisu than 20m.

So, now i explain my crash (whitout any broken part on my Phantom 4 Pro).

Link to download the aircraft log :
https://www.dropbox.com/s/0033hyy25imfeqr/FLY188.DAT?dl=0

I fly at 400 meters of the take off point (home point recorded and set for RTH). I am in sport mode (no collision detector). I follow a motorbike on a road with the mountain on the right and clear field on the left, the drone is positioned on the left side.

I lose VIDEO signal, and i think RC signal. The RC make bip bip bip and i have a popup on my screen (Ipad Air 2) and i click on the right box of this popup : i don't remind what is this popup, but i think it is initialize rth CANCEL or OK (could someone confirm me ?). The RC makes bip bip bip bip and nothing happens, i move the stick to up and forward nothing, i press rth nothing. finally the drone was crashed in a small tree on the right side of the road.

I have analyzed log with Airdata, it inform me that i have a data lose, but not anny RTH sequence recorder (logical if i don't have RC signal, not any more log recorded, right?). I analyze the aircraft log the drone don't stop it at all and go at 50 km/h in the tree at the same alitude and in the same direction.

I would like to understand if this is a pilot error or a DJI issue.

I have sent an email at DJI to share the log.

Do you have ani advises or info about this case ?

Thanks :-)

2017-6-26
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Nigel_
Captain
Flight distance : 388642 ft
United Kingdom
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The drone should stop if it doesn't have a command to say keep going.  Sounds like you told it to fly forwards when you couldn't see where it was going because the video had frozen, at 50Kph it doesn't take long to fly into a tree.

If you look in the aircraft log, you should be able to see the control stick inputs and the speed so you can see if you were telling it to fly forwards.  It takes the P4 about 10 seconds to accelerate to full speed and the same to slow down again.

If you can't see the stick inputs in the log, try https://datfile.net/index.html and export a csv file to look at...
2017-6-26
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Xavier1984
First Officer
Flight distance : 641171 ft
Switzerland
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Nigel_ Posted at 2017-6-26 02:31
The drone should stop if it doesn't have a command to say keep going.  Sounds like you told it to fly forwards when you couldn't see where it was going because the video had frozen, at 50Kph it doesn't take long to fly into a tree.

If you look in the aircraft log, you should be able to see the control stick inputs and the speed so you can see if you were telling it to fly forwards.  It takes the P4 about 10 seconds to accelerate to full speed and the same to slow down again.

I have checked: the drone goes in the right direction (Nord - West) with speed up and stick forward !

I also learn that when a RTH is initialized, a popup comes to CANCEL or not the RTH, and i have clicked on the right box : it seems this signify "cancel RTH".
2017-6-26
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Xavier1984
First Officer
Flight distance : 641171 ft
Switzerland
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- ADDED DOWNLOADABLE LOG IN FIRST POST -

In the log i see RC_input_throttle. So the Aircraft have the connexion with the remote, so, i just lose the video signal. Why a RTH initialization in this case?

In the field RC_STATUS i have a 4 -> receiver and remote control are disconnected. What is the difference with a 5 -> receiver and flight controller are disconnected ?

2017-6-26
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Nigel_
Captain
Flight distance : 388642 ft
United Kingdom
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Xavier1984 Posted at 2017-6-26 03:34
I have checked: the drone goes in the right direction (Nord - West) with speed up and stick forward !

I also learn that when a RTH is initialized, a popup comes to CANCEL or not the RTH, and i have clicked on the right box : it seems this signify "cancel RTH".

I think you only get the RTH popup if it does RTH due to low battery, then it is normal you get 10 seconds to decide.  If it does RTH due to no communications then it will not display the popup.  If you cancel it then you can still press the RTH button again, although you can also cancel RTH with the RTH button so you need to be careful and check the state.
2017-6-26
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Xavier1984
First Officer
Flight distance : 641171 ft
Switzerland
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I had : black screen -> no signal -> popup (click on right box) -> RC : bip bip bip bip bip (the RC bip always since a come back to the drone)-> nothing -> move stick -> press RTH button -> nothing -> crash at a moment
2017-6-26
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BudWalker
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Flight distance : 150919 ft
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United States
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The P4P never initiated RTH. At 514.46 the P4P was at -15.2 meters height, the signal strength dropped from 100% to 0%, and the P4P became disconnected from the RC. See 1st attached. Since it was disconnected the P4P didn't recieve the RTH command.
The failsafe was set to Landing which the P4P did when it became disconnected from the RC. See attached #2. The P4p must have been very close to the tree because the motorSpeeds dropped less than a second later.
Xavier1984.jpg
Xavier1984.2.jpg
Xavier1984.3.jpg
2017-6-27
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method007
First Officer
Flight distance : 110449 ft
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United States
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Well, that pretty much sums it all up.  Thanks BudWalker.  
2017-6-27
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Xavier1984
First Officer
Flight distance : 641171 ft
Greece
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Hi, thank you very much for this deep analyse! It signify that the failsafe is set over the dji go 4 application to land directly and not to active a rth process ?
2017-6-27
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Antonio76
Captain
Flight distance : 144403 ft
Denmark
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BudWalker Posted at 2017-6-27 07:04
The P4P never initiated RTH. At 514.46 the P4P was at -15.2 meters height, the signal strength dropped from 100% to 0%, and the P4P became disconnected from the RC. See 1st attached. Since it was disconnected the P4P didn't recieve the RTH command.
The failsafe was set to Landing which the P4P did when it became disconnected from the RC. See attached #2. The P4p must have been very close to the tree because the motorSpeeds dropped less than a second later.

BudWalker, awesome! The charts you included are from a website or do you have some special software to read the logs, in both cases, which?  Thank you!
2017-6-27
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BudWalker
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Antonio76 Posted at 2017-6-27 10:25
BudWalker, awesome! The charts you included are from a website or do you have some special software to read the logs, in both cases, which?  Thank you!

Take a look here

http://www.datfile.net/index.html
2017-6-27
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Antonio76
Captain
Flight distance : 144403 ft
Denmark
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BudWalker Posted at 2017-6-27 12:28
Take a look here

http://www.datfile.net/index.html

WOW! I'm impressed! Thank you soo much
2017-6-27
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Xavier1984
First Officer
Flight distance : 641171 ft
Greece
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I Will test with this software! So the failsafe is settable in the app: land - rth ? Or depending the current altitude the process change. I ask this because I take off at 0m  and I go under 0m due to the small hill.
2017-6-27
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Xavier1984
First Officer
Flight distance : 641171 ft
Greece
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Hi any news about my Las question? Is my crash a pilot error or dji issue ? The customer service would like that I send back the drone for a checkup!!! This is just a joke. They have the log and they have the possibility to analyse it.

Is there someone from dji / moderator / admin that can help me please?

Thanks
2017-6-30
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