One minute of horror after 65 flights. What was the cause?

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Hi everyone, maybe someone has had a similar experience to what happened to me today.
Something really weird. I was going to film over the water (7th time) and I placed my ph2 last version on a cement pier. Gopro was on, not recording, wifi gopro is always off. I flight by sight.
I haven’t changed anything compared to previous flight.
I noticed always immediately that the light was blinking red and yellow (this was my very first time).
I don’t calibrate anymore my PH unless I change something important. This location was new but only 5 km away from previous location. So I recalibrated the PH 360° by orizzontal and vertical turn. All lights turned green. I placed it down again, and waited for the green lights and 2 series of fast blinking green. All was green and I waited an extra 30 seconds to be sure. The moment I took off (in GPS mode) I realized it did not look and was going on his own. Red and yellow were blinking again. I tried to recover but had a feeling that the directions was responding because were wrong. So I ignored the movement of the sticks and concetrated to bring my PH back (flying over water). I managed to catch it while flying by near me. I think I must have turned white. Just because I kept cool and had experience I was able to recover. A newbie would probably would have crashed.
So I went home, connected to the pc and the message appeared “Gps not calibrated or magnetic field interference”. Strange also the IOC was off when normally it should be on.
So now I made a reset and calibration at home. Wonder if any of you had the same issue. I’m 100% sure this is not satellite related. I tried to search in internet to see if there is some magnetic field issue at the moment (sun spots that create storm) and it appears there are some disturbances at the moment and will peak tomorrow in a minor storm. I doubt this was the cause. What is really disturbing was that after I calibrated everything was green and the moment I took off it just moved on it's own. I think I will make a test flight on a open field now.
 
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Almost certainly it was magnetic interference to the compass from metal strengthening rods embedded in the concrete that you took off from.
 

ianwood

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Meta4

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Completely unrelated to GPS or solar activity.
As already advised, it's all about trying to calibrate your Phantom in an area that had a strong magnetic field because of the amount of steel reinforcing in the concrete. If you tried a compass there, you'd see that the compass doesn't point north there either.

Your Phantom was telling you that the magnetic field it detected was significantly different from what it is used to and expects.
You calibrated it in the magnetic field so that it now where north was with the magnetic interference present.
But when you took off and flew away from the concrete and it's field, your compass no longer knows where north is because it's still adjusting for the magnetic field it has now flown away from..

This shows the danger of recalibrating unnecessarily.
At 5 km from home, there is no difference in the earth's magnetic field and no need to recalibrate.
You could travel 100 miles (possibly much more) without needing to recalibrate.
If you have a good calibration, don't mess with it unless there is a good reason to - and that doesn't include traveling 5 miles.
 
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Concrete slabs, metal link fences, metal garage doors, metal hangar door, vehicle roofs etc etc. Not the place to recalibrate a compass which was already calibrated. Calibrating on/near any of these which is also near water is asking for a dunking :D

splash.jpg
 
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Thank you for the help. Just returned from my training and testing field. Everything seems ok. Next time I will take a compass with me to put on the ground. I already read about possible rods in a floor can create problems, but I haven't read that this has been really proven.
 
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Also, concrete often has embedded conduits which are metal and have fields caused by the electrical currents inside. If the bird thanks all of the concrete and steel are north, then every direction that it moves away is south. It gets very confused quickly.
 

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Thank you for the help. Just returned from my training and testing field. Everything seems ok. Next time I will take a compass with me to put on the ground. I already read about possible rods in a floor can create problems, but I haven't read that this has been really proven.
Download a gauss app to your phone and use that.
 
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This is really helpful to those of us who are new. Thanks for the very detailed post about the problem and the well thought out answers!
Chris
 

ianwood

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Alternating red and yellow is the error code for bad compass calibration.
Not to be pedantic but it doesn't mean a bad calibration per se. It means the compass is getting a reading that is outside of an expected range. A bad calibration is one potential cause for an implausible reading.
 
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I noticed always immediately that the light was blinking red and yellow (this was my very first time).
.
If this does happen..
Find a box or a different take off point.

If you are insecure and really need to a do compass calibration, get your google maps out and find an open field.
 
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Completely unrelated to GPS or solar activity.
As already advised, it's all about trying to calibrate your Phantom in an area that had a strong magnetic field because of the amount of steel reinforcing in the concrete. If you tried a compass there, you'd see that the compass doesn't point north there either.

Your Phantom was telling you that the magnetic field it detected was significantly different from what it is used to and expects.
You calibrated it in the magnetic field so that it now where north was with the magnetic interference present.
But when you took off and flew away from the concrete and it's field, your compass no longer knows where north is because it's still adjusting for the magnetic field it has now flown away from..

This shows the danger of recalibrating unnecessarily.
At 5 km from home, there is no difference in the earth's magnetic field and no need to recalibrate.
You could travel 100 miles (possibly much more) without needing to recalibrate.
If you have a good calibration, don't mess with it unless there is a good reason to - and that doesn't include traveling 5 miles.
i calibrate my bird everytime I fly. is that bad?
 
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ianwood, nice write up!

I, like N017RW, have only calibrated mine a few times....

I have seen no definitive study done yet on flyaways where calibrate or not just before the event was compiled, but standing back and just looking at the macro picture of all I have read here and on dji.com forum over the last 4-6 months, it SEEMS to me that MOST flyaways happened to people who DID calibrate just beforehand.....

I base my NO CALIBRATE on this seeming data until it is proven wrong. I also go with the KISS principal and why try to fix something that is not broken?
 

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i calibrate my bird everytime I fly. is that bad?
for some reason it makes me feel safe when i calibrate every flight so if a flyaway does happen and I come back here to cry about it I won't hear the "you didn't calibrate blah blah".
The calibrate every time school of thought comes out of not understanding what calibration does and when it is necessary and becomes a superstitious ritual to make you feel better.
Calibrating every time makes as much sense as pushing the elevator button 5 times to make it arrive sooner, and as show in the original post can cause problems.

Understanding compass calibration rather than having a calibration superstition helps you to fly better.
 
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