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- Aug 21, 2014
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Even a P3A plagued with compass errors is still flyable (this is the 3rd craft DJI sent me...which is still defective)
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It has to switch to ATTI because without the compass, it doesn't know which way it's pointing. GPS only tells it where it is at any given time, not which way to go.I too have had compass error problems, but mine were caused by flying above 15m steel streetlight poles at about 25m. I still don't understand why it has to switch from gps to atti on a compass error. It is certainly disconcerting when it suddenly changes & begins to drift with the wind. That is a good reason why we all need to be proficient in flying atti mode. Any large steel structure will become magnetised by the earth's field, and/or any current flowing through the conductors in a high voltage line, but my experiences suggest that it is the [semi]permanent magnetisation of the actual structure which causes the most problems.
That's right. The frequency response of the magnetometers irolls off well below 60 HZ. But, I was surprised to find out that some power lines have a magnetic field that oscillates within the magnetometers frequency response. The oscillation in this plot is 1.44 HZPeople, 230 kV AC lines really won't do anything to your compass, during this flight section no errors were reported. AC changes polarity 60 times per second, thus a compass remains still. If I was flying over a dc line that's another story.
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Your right about the dc volts and EMF. AC will cause electrical fields EF, but they still affect the compass, these fields will not travel as far as emf (dc) but still will cause your birds compass to be affected (if you are close enough). Many of us have had this condition affect our bird.People, 230 kV AC lines really won't do anything to your compass, during this flight section no errors were reported. AC changes polarity 60 times per second, thus a compass remains still. If I was flying over a dc line that's another story.
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That's right. The frequency response of the magnetometers irolls off well below 60 HZ. But, I was surprised to find out that some power lines have a magnetic field that oscillates within the magnetometers frequency response. The oscillation in this plot is 1.44 HZ
View attachment 67657
and is occurring when the P3 comes close to these power lines.
View attachment 67658
My theory is that this 1.44 HZ oscillation is excited when load and generator is slightly out of phase. I'm just rambling here, I know almost nothing about electric power generation and delivery. But, I do know this is just a magnetic field, not an electromagnetic field, since at 1.44 HZ this is clearly the near field effect.