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Signal loss in atti mode
2413 16 2017-5-6
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MaxBDS
lvl.4
Flight distance : 161437 ft
Italy
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I have a silly question: what if the P3S loses the signal with the RC while flying in ATTI mode? Does not having activated GPS can do the RTH? I'm trying to practice this mode (ATTI) but during the tests I had this doubt
Thank you
Max

2017-5-6
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kndll
Captain
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Canada
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since you started with P-GPS  and then switched to ATTI ,    RTH will work if signal is lost between RC and AC ,   home point was  established before take off and  GPS will be used for RTH , your GPS receiver in the phantom would have to fail or all of the satellites to fall for RTH not to work .
2017-5-6
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MaxBDS
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Thank you Kndll.
Obviously before takeoff I take all the necessary precautions (P-Mode, RTH position and altitude, etc.) after the standard flight step in ATTI mode and try to control the drone without the help of the GPS. The doubt I had when the Phantom went away at about 100 mt and I was afraid of an ever-possible signal loss. Then switching to P-Mode would have no effect and hence the doubt!
Thanks again
2017-5-6
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Bradders
Second Officer
Flight distance : 862283 ft
United Kingdom
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YEs in ATTI it would just hover mid flight, or if you had GPS before flight it will return to that location as long as it has a GPS signal
2017-5-8
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Phantomski
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and if gps is gone, i think it will either hover and land when battery is low, or it will land immediately, the best it can with no gps...   i am guessing.. do not know for sure, but i think that's a failsafe mode mentioned in the manuals....
2017-5-8
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Mark The Droner
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The last two posts confuse me.  Just to be clear:

In GPS mode, if it loses signal, it will Failsafe, which if set to RTH, it will return to home.

In ATTI mode, if it loses signal, it will Failsafe, which if set to RTH, it will return to home.

Failsafe/RTH will work regardless of the mode.  Exception, of course, is if the AC actually loses the number of satellites required for GPS for whatever reason.  

2017-5-8
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Phantomski
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Mark The Droner Posted at 2017-5-8 13:47
The last two posts confuse me.  Just to be clear:

In GPS mode, if it loses signal, it will Failsafe, which if set to RTH, it will return to home.

u got it, i was just mentioning what would happen if u actually DID lose GPS...
2017-5-8
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MaxBDS
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Hi Mark
Thank you for your answer! Even the latest messages have confused me! I know perfectly well that if my Phantom GPS receiver fails or if all orbit satellites fall off!!! ... the RTH function would not work! My question, perhaps stupid, is: What happens if I switch from P-Mode (RTH memorized before take off) to "ATTI" and I lose the signal between RC and Phantom? Obviously this live test would like to avoid it! Is there any DJI- Jamie that can give me a certain answer? Thank you!
2017-5-11
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Mark The Droner
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Hi = The Phantom doesn't need a connection to come home in ATTI mode.  It's not that ATTI mode doesn't have GPS.  ATTI mode simply ignores GPS unless it needs it for Failsafe.  So if it loses the control signal, it will failsafe/RTH successfully.  
2017-5-11
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MaxBDS
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Thanks MarK,
You have been very clear! I hope your answer will be useful to other beginners who have had my doubts as well!
Thank you again.
Max
2017-5-11
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Soren O
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Denmark
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Mark The Droner Posted at 2017-5-11 02:01
Hi = The Phantom doesn't need a connection to come home in ATTI mode.  It's not that ATTI mode doesn't have GPS.  ATTI mode simply ignores GPS unless it needs it for Failsafe.  So if it loses the control signal, it will failsafe/RTH successfully.

Hi...I interrupt this conversation:  If you go to atti mode like the example you give, and you fly atti because you are far north close to the N.Pole, (reason to fly atti) - you say tha the drone ill go back in P-mode - which in this example would be very bad. Is there a way to ensure the drone stays in ATTI?
2018-3-26
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Labroides
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Soren O Posted at 2018-3-26 13:00
Hi...I interrupt this conversation:  If you go to atti mode like the example you give, and you fly atti because you are far north close to the N.Pole, (reason to fly atti) - you say tha the drone ill go back in P-mode - which in this example would be very bad. Is there a way to ensure the drone stays in ATTI?

Switching to atti mode will cause the Flight Controller to ignore GPS data.
That won't help you at all if you are close to the N Pole and having compass issues.
You will still have the compass issues.
2018-3-26
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Mark The Droner
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Soren O Posted at 2018-3-26 13:00
Hi...I interrupt this conversation:  If you go to atti mode like the example you give, and you fly atti because you are far north close to the N.Pole, (reason to fly atti) - you say tha the drone ill go back in P-mode - which in this example would be very bad. Is there a way to ensure the drone stays in ATTI?

P mode is only P mode if you have a signal.  And in P mode, the AC flies with GPS.  Atti Mode is only Atti mode if you have a signal.  In ATTI mode, the AC ignores GPS.  If you lose signal, your AC goes to failsafe which is neither P mode nor ATTI mode.  And in failsafe, GPS works regardless of how you have set your controller.  

The North pole is another problematic situation altogether involving the compass which obviously won't work correctly.  Yes, losing signal while flying close to magnetic north would cause RTH to become unreliable.  So you would solve the problem in advance.  You would think ahead.  One solution might be to set your failsafe to something else other than RTH - such as hover or land.  
2018-3-26
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Labroides
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Mark The Droner Posted at 2018-3-26 14:01
P mode is only P mode if you have a signal.  And in P mode, the AC flies with GPS.  Atti Mode is only Atti mode if you have a signal.  In ATTI mode, the AC ignores GPS.  If you lose signal, your AC goes to failsafe which is neither P mode nor ATTI mode.  And in failsafe, GPS works regardless of how you have set your controller.  

The North pole is another problematic situation altogether involving the compass which obviously won't work correctly.  Yes, losing signal while flying close to magnetic north would cause RTH to become unreliable.  So you would solve the problem in advance.  You would think ahead.  One solution might be to set your failsafe to something else other than RTH - such as hover or land.

Yes, losing signal while flying close to magnetic north would cause RTH to become unreliable.

Flying close to the North Pole would involve compass problems that exist whether in atti mode or P-GPS mode or any other mode.
Switching to atti mode doesn't do anything to help with compass errors.
2018-3-26
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Bashy
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Labroides Posted at 2018-3-26 14:05
Yes, losing signal while flying close to magnetic north would cause RTH to become unreliable.
Flying close to the North Pole would involve compass problems that exist whether in atti mode or P-GPS mode or any other mode.
Switching to atti mode doesn't do anything to help with compass errors.

Switching to atti mode doesn't do anything to help with compass errors.

Thats good to know for future reference, thanks

To OP, From what i was told before RTH is another mode, GPS, SPORTS, ATTI, RTH, all independent modes.
2018-3-26
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Mark The Droner
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Labroides Posted at 2018-3-26 14:05
Switching to atti mode doesn't do anything to help with compass errors.

I admit I don't have any personal experience in compass errors during flight, but your comment is contrary to what I've read in many other threads.  People are always posting "If you have a compass error, go to ATTI."  And apparently there have been Go warning messages to advise pilot to switch to ATTI during compass errors.  Why do they say that?  I don't know.

https://forum.dji.com/thread-108827-1-1.html

https://forum.dji.com/thread-52515-1-1.html

https://forum.dji.com/thread-112713-2-1.html

https://forum.dji.com/thread-8253-1-1.html

https://forum.dji.com/thread-50211-1-1.html
2018-3-27
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Labroides
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Mark The Droner Posted at 2018-3-27 04:29
I admit I don't have any personal experience in compass errors during flight, but your comment is contrary to what I've read in many other threads.  People are always posting "If you have a compass error, go to ATTI."  And apparently there have been Go warning messages to advise pilot to switch to ATTI during compass errors.  Why do they say that?  I don't know.

https://forum.dji.com/thread-108827-1-1.html

I would say that a lot of things you read here are poorly informed or just plain wrong.
People love to repeat what they have heard without understanding it.
How many times do you see comments on flight incidents where people suggest the cause was not calibrating the compass or that the homepoint was not recorded.

And the DJI Go error message is standard DJI poorly written.
Look at the flight data and you see that the Phantom has usually dropped GPS data, putting the Phantom in atti mode by the time that message appears.
By then flicking the flight mode switch won't achieve anything.
2018-3-27
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