questions on phantom3 pro failsafe

[mj2019]

hello all, ive just passed by my first experience ever with phantom3pro and dji hardware going before the satellite era!!

i wanted to make a video for a friend some circles around his house, i took off with 14 locked satellites, i was concentrating on the settings of exposure when i felt the p3 flying toooo fast , as i checked the screen oh 0 satellites locked!! i was a bit far some 400 or 500 yards my friend was spotting with me, any way as i came back and descended to 20 feet every thing was fine 14 , 16 ... satellites once i go higher they start to disappear!! this repeatedly happened 5 times!!! what may cause this did it happen with any one and he found an answer??
i will open the shell to check the gps but a more beginner embarrassing question is revolving ever since the incidence , i know if in rc range the p3 will fly without satellite lock, but what happens if rc link disconnects too??? am a student from beta flight but never asked my self what is the dji failsafe in case of both rc loss after gps loss??? is it land or alt hold or what???

 

[Deleted member 62848]

Nothing mounted on top of shell that would block GPS? This bit tricky question and to me sounds like a GPS fault,,it should hold all sats when in normal flight unless atti mode is engaged ,,
There is no failsafe if there is no GPS to lock it in hover or land or rth ,it will drift or probably go into a crash scenario ,,opening the shell is pointless unless your goin to change GPS module,,your better to upload the flight log so someone can confirm what happened and point you in what to replace if needed,,its just guessing without any log as to what went on,,if rc disconnect when it got GPS it will do what is set in loss of signal settings,either hover or land or rth,,if no GPS it dont know what to do which can get scary,,5 times ain't good so mayby imu and compass needs checking in app or upload the flight log

 

[Meta4]

as i came back and descended to 20 feet every thing was fine 14 , 16 ... satellites once i go higher they start to disappear!! this repeatedly happened 5 times!!! what may cause this did it happen with any one and he found an answer??

I've seen similar reports a few times - mostly from locations in Russia.
I would suspect there is some GPS jamming somewhere near where you were flying.
You could check to confirm this is not a problem with your drone, by flying somewhere else >10 km away from where the problem occurred.

i know if in rc range the p3 will fly without satellite lock, but what happens if rc link disconnects too??? am a student from beta flight but never asked my self what is the dji failsafe in case of both rc loss after gps loss??? is it land or alt hold or what???

On loss of control signal, if the drone has no GPS signal, it will just land where it is.

 

[Deleted member 62848]

Ah ok was unsure on that loss of GPS,I thought it would drift and not land,
That cleared that up for me

 

[Meta4]

Ah ok was unsure on that loss of GPS,I thought it would drift and not land,

Neither landing nor drifting is a perfect solution.
Either way it could end badly.
Fortunately, it's very rare to be in a situation where you have no GPS and lose control signal.

 

[mj2019]

hello guys , let me report the tests ive just done, am on a vacation soi had the time to carry out what was happening and make some useful conclusions and share them here, first i went to the same location with another phantom3 pro i started with more than 9 locked sats then 13 or more then the problem replicated exactly the same !!! first conclusion bird 1 was not guilty, i kept moving up and down in altitude i determined that from 90 ft to 500 ft the problem appears below or above the gps locks fine with no glitch andi even noticed that even in the bad zone of altitude moving around is better than hovering at least 2 or even 5 sats still appear, i hesitated a lot to try to turn off the transmitter and check if the p3pro will land (as some members suggested that with gps loss and rc loss landing will happen) .

 

[mj2019]

now the biggest problem is how to live with this that location is where i usually fly, here are my concerns, first for the phantom3 pro i usually set the rth altitude at 300 ft, so in case i was flying even below the 90ft and rc link lost the p3 will start to ascend to the 300ft it will get to the gps dead zone so maybe will start to land but as it descends it may catch gps signal what will happen will it continue to land or go back to rth mode????? we need some one who is very talented in those scenarios for us as pilots and users to learn.

 

[mj2019]

concerning the reason for all this i dont know its either a new communication tower orrr a near by small mini hill like some 300 or 400 ft in altitude above that location some 3 miles or less there is a small radar its ran by the civil aviation related to an air port that is 30 miles away but it has always been there years ago with no troubles earlier to this week!! i dont suspect a jammer who isgoing to have a jammer in the neigbour hood in country side!

 

[mj2019]

i hope freinds here and guys i invited from other threads will cooperate to give scientific answers to all this , so in case such a scenario we will learn take the best reaction

 

[cheddarman]

Very strange scenario. Is there a hill near there which you could carry the drone up to those "no GPS" altitude and see if it's the same problem.
If it is, look at your phone and see if it has a GPS signal - download a GPS checker App.
If it proves that the GPS signal is missing, go somewhere else to fly!

 

[mj2019]

Very strange scenario. Is there a hill near there which you could carry the drone up to those "no GPS" altitude and see if it's the same problem.
If it is, look at your phone and see if it has a GPS signal - download a GPS checker App.
If it proves that the GPS signal is missing, go somewhere else to fly!

i use the app on phone while it is in flight mode, to avoid getting a call in the mid flight, by the way phones use gprs that may depend on network provider and give location regardless of sats so testing gps location by phone is not accurate i have a very old garmin i will use that to test instead !amm gona investgate this , but always sharring and suggestions will shrink the trip cause others may have just passed similar experience and solved what is needed to be solved

 

[cheddarman]

Yes, the Garmin will tell you whether there is a satellite problem in the area...............

 

[mj2019]

Yes, the Garmin will tell you whether there is a satellite problem in the area...............

well this suggestion gave the 100% confirmation of the presence of some thing rendering the gps useless at a certain area ,i drived out to a near mini hill close a mile away with the garmin in hand all the time the garmin was working perfectly , until i went to a point facing north at the suspected altitude only a couple of meters away from that point every thing was fine , but once i stepped there no gps, was detected by garmin!! and more over as i put the garmin on sat detection mode, i gives every couple of seconds a strong signal of some sats as if in a pattern repeatedly but will no location can be detected ... acouple of meters away the gps goes fine again!!!
you are welcome all what areyour suggestions or assumptions to those test results??
and i would like to continue this thread latter towards detailed discussion into how the dji p3 program in the flight controller respond to every case of failure or unusual condition(in terms of errors of speed ,gps ,altitude, compass, battery,....)

 

[cheddarman]

Very interesting, didn't know GPS satellite signals could be blocked in a specific area. Where exactly are you, Log/Lat coordinates if possible.

Just possible that someone doesn't want drones flying there?

Are there any vehicles near where you fly. It is possible that someone has a jammer fitted in their vehicle.

 

[mj2019]

Very interesting, didn't know GPS satellite signals could be blocked in a specific area. Where exactly are you, Log/Lat coordinates if possible.

Just possible that someone doesn't want drones flying there?

Are there any vehicles near where you fly. It is possible that someone has a jammer fitted in their vehicle.

ill work on shrinking down the area to discover the cause , there are a group of buildings of only 4 or 5 floors and a group of houses, am hesitant the jammer theory cause i flew at different times during the day so its not possible the jammer is always on!! it seems some thing related to telecommunication is causing this big trouble.

 

[cheddarman]

It is quite possible that a jammer could be on 27/7, depends why someone is doing it where you fly.

GPS Technology operates in the following frequency bands:

GPS L1 Band: 1575.42 MHz with a bandwidth of 15.345 MHz
GPS L2 Band: 1227.6 MHz with a bandwidth of 11 MHz
GPS L5 Band: 1176.45 MHz with a bandwidth of 12.5 MHz

Anybody operating a transmitter of some sort at those frequencies will interfere or jam the signals.

 

[Deleted member 62848]

What country you in,,I just read its illegal to use drone jammers unless it's a federal department in all of United states of America but they out there,,,they sell for as cheap as $ 50

 

[mj2019]

no am not in the US, ill check the internet provider in the area an engineer told me they might use such bands , and this should be a very new change they have done i only noticed this less than a week ago!

 

[mj2019]

so the first question we need to answer first for the phantom3 pro i usually set the rth altitude at 300 ft, so in case i was flying even below the 90ft and rc link lost the p3 will start to ascend to the 300ft in order to return to home but it will get to the gps dead zone so maybe will start to land ( not sure others told me it drifts in atti mode) but as it descends it may catch gps signal again what will happen will it continue to land or go back to rth mode? we need some one who is from dji or deeply knows the program run by Flight controller on the p3

 

[Deleted member 62848]

Well you could bring your rth height lower if no objects around that high,,rth setting is much the same over most phantoms ,,pretty annoying your issue going on ,,its a strange one,,but something is causing it since happen with 2 p3ps ,,jammers are world wide and I mention USA because that was first article I read,,normally atti mode engages when insufficient GPS is available and will drift but from above post it will auto land where it is if GPS is lost during rth,,,you seem to have found a certain dead zone and reasons unknown and never be know,,phantoms are really good at giving us a challenge sometimes with issues not even dji knows about,I been following this cause I to would like to know what goes on and hope you find out,its handy for future knowledge, as mention your flight log will show what happen but it wont say why GPS was lost ,,very tricky issue

Just want to add,,there is over clever problem solvers on this forum,,if you search in forums you will see some have lost GPS in the past but never to this issue your having trouble with so you probably wont get a definite awnser or a fix apart from not flying there or avoiding that height in that area,it makes it very hard and I bet a lot are stumped,,we are nearly in the Jetsons era now so we can expect the unexpected with all the new technology coming out,,its hard to answer something no one has come across so congratulations on that part,,I really hope you find out but dont hold your breath cause might not happen,,mayby it's just a complete dead zone not that I've heard of that but never know,,might be area 52 lol,best of luck though for a result