PA32R, thanks for your inquiry!
1. I applied full power to try to stop the fall, not knowing it was inverted. I was within maybe ten feet of the takeoff and crash site, having only taken the drone to maximum altitude to snap one photograph of my house and lake. My readout on altitude runs about 25 feet in error all the time so I assume it was under 400 feet but I have no way to know for sure. I had just snapped the picture at the maximum altitude and started the descent and a few seconds later, the drone suddenly accelerated its downward travel. I was close enough to tell it was inverted after I realized that full power was not working. I saw the drone hit in the soft dirt and bounce about a foot high, then come to rest still in the upside down position,. The propellers were all bent and broken in this direction and the camera had hit the bottom of the gray area so hard that it dented the material. It is a perfect match with the camera ring, the part that surrounds the lens. The ground was soft because we had received 1.57 inches of rainfall the previous day and the crash site was my front yard, with grass and leaves serving as padding I suppose. Anyway, the drone did not have a soft landing giving the dent the camera caused. I luckily managed to make a video of this dent and camera relation along with a video of the drone some 15 seconds after the crash. The video shows all lights on, the battery with 3 LED's lit and one blinking and the drone waiting on its next command. On the cell phone video, one can hear the clicking of the data transmitter still functioning! In fact, I cleaned the mud out of one of the motors and installed 4 new props and flew it about 30 minutes after the crash. Had the gimbal not been jammed, I would not have sent it to DJI as the only other damage was slight dents in two of the arms that support the motors. AND, had it hit the ground right side up, as you indicated might have happened, the propellers would not have been damaged in the direction of fall and the camera and gimble would have been broken off and the landing strutts warped or broken off. None of this occurred! The entire brunt of the crash was to the top of the drone, meaning that it was upside down!
2. Like I said, the altitude error is and has always been off by 20 to 30 feet except at very low heights. No amount of calibration had ever corrected it so I quit trying, knowing DJI's history of service. My maximum altitude in Litchi was set to 122 meters, which I believe is very near 400 feet and giving the builtin error, I stand by my statement.
SO, any ideas why the Phantom 4 flipped over? Nope, and neither has anyone else on any of the 4 forums either. Of course, it is always a bird strike, or a missing propeller, or a gust of wind, or a UFO, etc. But as you probably know, you can manually flip a Phantom over at say 6 feet altitude and let it go and it will not crash into the ground. It will quickly right itself and hover at about the same altitude you released it at. If a prop had come loose, the drone would not have made a perfect pancake landing but instead would have been spinning out of control in all 3 axis. Same with the gust of wind, it would have immediately corrected its attitude and continued to fly. As far as the UFO, well you got me there.
Any suggestions would be appreciated!
Thanks,
Jim
WA5TEF
