What does "Sensor Bias" is too big mean"

[pianoflyer]

Hi, in reading the manual and trying to understand everything, I see a flashing 3 red LEDs means "Not stationary or sensor bias is too high". what does that mean and what is "sensor bias
" anyways?
Thanks

 

[EMCSQUAR]

It means your sticks need calibration

 

[J.James]

Or your compass is so out of calibration that it needs to be calibrated to bring the values with in an acceptable range.

 

[thestone11]

Are you in phantom mode or naza m mode? LED lights can mean different things between the two modes!