Been very busy lately, we really need to add more hours to the day...
Bart, your email system alerted me to the post, works great!
To answer the question, how do I find the issue....
If it's something that I've done incorrectly, I very simply go back through my setup, mechanical AND electronic. Here's an example, recently testing a new hexacopter, the initial hover was fine, climbed up to appx 8 ft where it stared a massive oscillation, front to back.
I lowered the throttle, trying to time the oscillations to land it on its feet, but it still ended up on its side, breaking a prop or two, but no other damage.
What I found was that I had written in an incorrect value in the X axis, basically a + instead of - in the IMU setting. Why? Probably distracted, by a phone call, walk in customer, any of 100 things.
My theory on why it hovered initially, THEN started trying to flip? I try to keep the values to a minimum, so while the value was the wrong direction, it wasn't far off. So on liftoff, straight up, it had no issues. But once it encountered some wind, requiring the autopilot to correct for an upset, the negative value sent the correction in the wrong direction... Then how did it just not flip over? MY correction input on the sticks! So basically me and the IMU are fighting one another for level!
Going through the setup again on the bench, verifying my values, is where I find the discrepancy. Subsequent test flights were uneventful, shipped it out last Thursday to the customer.
In the event that I can't find anything mechanically wrong, or in my setup, then I prefer to fly with a DJI OSD MKII, with the data logging capability. With this unit, you can review the logs, see if there was an electronic discrepancy, AND you can send these logs to DJI for analysis.
The point of all this is, as I wrote earlier, it's easy to blame the unit, the aircraft, the wind, the sun, the planet alignments, whatever. But FIRST we should check our own inputs, maybe even have another set of eyes check our work. As a full scale helicopter and commercial airliner mechanic, I ALWAYS had another mechanic look at my work, and I checked theirs. Not because I was a bad mechanic, because I was a good one.
