My son and I go out flying in the field out front and some times other locations together, about four times a week, with three batteries each per quad.
Before finding this technique they could regularly (several times a session) drop out the sky, but not predictably. The pattern often was after taking them really high and bringing them down hard would cause the issue (no banking). But it could happen quickly after lift off too whilst messing around. We saw many posts with theories and tried most of them out, but decided there was no pattern, like the banking idea.
I have not had mine drop since, other than a few times where I can pin it back to not doing this calibration or having moved up the field and flying below the level we are started at, standing looking down on the drones from higher up the slope.
My Son has had a few more drops than me, (again not many really) but he is into FPV racing drones, so pushes the envelope much more than I do and hits it on the ground more. So some of these may be due to other things like straw in the motor gears or loose battery etc. One of the HXT connectors on one of our batteries had no solder on it, was just pushed into the connector, I discovered this last night, so that might have been root cause of a couple of his fails, and motor has at failed a few times catching broken guards and thus safety cut out.
One X8HC and other is X8HW both experience same frequency of these drops I would say.
I'm not saying this is the cure - merely what my anecdotal evidence is. I don't even think the calibration is the actually curing it, perhaps it is just a byproduct of the calibration resetting some other values in the controller board that helps prevent this occurring.
Switch on controller, do the usual up down to bind. Then before going to start the motors, make certain the quad is perfectly level and facing in the direction you want the headless to go (away from you). Now bring both stick to bottom left corner at the same time, the quad should respond with some flashes after a second or so. This calibrates the gyro for what is level. Now release the sticks and bring them down to the bottom left corner. Again the lights should respond on the drone. Release the sticks and you should be good to lift off. This should reset the headless bearing, I do both each time I start a new session, or move location to higher or lower location in elevation. You can do it after landing and turning the rotors off too, if you choose without having to restart the radio transmitter.
I stress that I'm just adding to the mad theories and ideas, but it seems to work for us and it feels like a logical explanation to me.
Regarding your banking idea, could this be a different issue, as if you have guards on, they can flex up (especially if they have hit the ground a few times) and foul the blades when banking hard, that can cause the motors to sometimes cut out as it thinks its hit something.- just a thought.
Tim.
