Problems with staying in GPS lock mode

Taytayholl · Jun 30, 2016

While flying recently I've noticed even though I am connected to what I would consider to be ample satellites (13-16) about 2 minutes into the flight my p3 professional will switch into attitude mode and back to GPS mode sporadically. Any ideas why this would be happening?

Gulfstream · Jun 30, 2016

If you are located in the Western U.S., there was a NOTAM published for the entire month in June re: GPS Interference Testing that was being conducted at China Lake NWS.

It affected GPS reliability down to 50ft. AGL -- Even some automotive manufacturers had issues.

That testing has concluded as of today, as far as I know. If you're located elsewhere then maybe it's just atmospheric conditions.

https://www.faasafety.gov/files/notices/2016/Jun/CHLK_16-08_GPS_Flight_Advisory.pdf

Taytayholl · Jun 30, 2016

Eastern US. The randomness of the flipping between flight modes and sometimes the speed of the flipping leads me to think it has to be something technological. Not saying it can't be atmospheric just would still be open to anymore troubleshooting

Andrea · Jun 30, 2016

Taytayholl said:
While flying recently I've noticed even though I am connected to what I would consider to be ample satellites (13-16) about 2 minutes into the flight my p3 professional will switch into attitude mode and back to GPS mode sporadically. Any ideas why this would be happening?

It happened to me as well a couple of times.
I think it has nothing to do with GPS.
It's more likely your compass.

Just my experience... but check the compass values.
Don't calibrate it everytime you lift off, but get used to check it's readings before flying.

Taytayholl · Jun 30, 2016

What would normal compass values look like?

alokbhargava · Jun 30, 2016

I had noticed varying GPS lock timings but once it was locked, I didn't see any issue. May be I fly in clear sky conditions.

Taytayholl · Jun 30, 2016

When I flew today it was very clear conditions. Did not take off until it had GPS lock still lost it a few minutes in then went into the cycle of GPS lock and attitude

Gulfstream · Jun 30, 2016

Taytayholl said:
When I flew today it was very clear conditions. Did not take off until it had GPS lock still lost it a few minutes in then went into the cycle of GPS lock and attitude

Maybe you can upload the flight logs to this site, and hopefully they can see the problem: https://www.phantomhelp.com/LogViewer/Upload/

* Make sure you post the link here so people can see it, and possibly offer a solution.

Andrea · Jul 1, 2016

Taytayholl said:
What would normal compass values look like?

The "module" (the final value) of the compass should be around 1.4. Please notice that this value is decomposed in its x, y, and z components that have to change when you move your craft, but the "sum" of those values (it's not the sum, but the square root of the sum of the quadratic of the tree components) should be almost constant, and close to 1.4.
In between 1.3 and 1.5 should be fine.

Mark The Droner · Jul 1, 2016

What's the satellite count as it's toggling?

AussieScott · Jul 1, 2016

I bought my second P3Adv and took it for it s first flights today. I had exactly the same problem, gps lock before take off. During close flights 100-200 meters a couple of times it lost the lock and then flicked back. 15 satellites lock. ???
My first P3A which i still fly has never done that .
Scott.

WetDog · Jul 1, 2016

I have been seeing this recently on both P3Ps. Comes up in odd places - like the middle of the ocean where you don't expect much 2.4GHz interference. I'm in Alaska, well away from China Lake. Unless the CG has put GPS jammers on their helicopters it is probably internal to the bird. I usually don't bother with compass calibrations although I did do it on both birds recently and still intermittently come up with the issue. I've just flown in ATTI mode for a few minutes and the problem goes away.

There are enough of these threads to indicate Something Happened recently. I'm guessing that DJI tweaked some firmware that downgraded GPS sensitivity or something - hard to know. We should probably keep talking about it and I should probably download my log files when this happens. Too busy taking pictures though and flying in ATTI is OK most times.

Something else that I've not noticed before is that if I put my hand over the GPS the P3 instantly squawks it's in ATTI mode. I've not noticed it being that twitchy before but I can't really recall if that is true or just something that has come to my attention.