The recent rains and snows in California have left a lot of image ready landscape out there. Today while driving in the desert I saw an image I had to get, the snow capped Sierra Nevadas on one side and the equally snow capped Panamints on another.
I got the P4 out of the case, inspect the aircraft, insert a battery, calibrate the compass, and get ready to fly for a few minutes. The battery had been in the case for a bit over a week and the temperature was cold, so it was not 100% but still showed over 55% and this was going to be a short hop. The intent was to climb to 100 feet, do a couple slow 360's with video running and then grab some stills in multiple directions, climb to about 200 and do it all again, and maybe up to 300 after that. Land and go home.
The launch point was about 40 feet north of my vehicle. I was just going to go straight up from that to do the imaging.
When I launched I ran it up to about 15 feet to check things out. I did notice the quad seemed to be less stable than I was accustomed to, drifting a bit in location and altitude. Not bad, just noticeably less stable. There was no wind. The quad seemed to stable out, so onward I went.
Up to 100 feet, take the video. Up to 180 feet and do the same thing. Most of the time eyes on the drone, but sometimes head down to see how the vid / pics were going. During one point while eyes on the drone I got 6 beeps from the tablet / controller, but when I looked down there was nothing unusual on the screen.
Just before I was going to land, and still hovering at 180 feet, I went head down for about 30 seconds, looking at the image on the tablet. At about the time I started to go eyes out to visually find the drone I realized it was getting louder, fast.
I looked up in time to see it plummeting downwards, level flight, all propellers turning, coming down very fast, faster than I have ever been able to make it descend. Further, it was centered right over my truck, which was behind me in relationship to the launch point. I went full up on the stick, but this did not slow the descent in the least.
The P4 impacted the center of the roof of my truck hard enough to dent the roof. Two of the blades got tangled in one of the antennas on the roof of the vehicle, causing a Motor Obstructed warning, the other two blades still turning.
After getting everything shut off I started looking at damage. Surprisingly there did not appear to be much, other than the dents in the top of the truck. One of the P4 blades was broken, from the marks apparently on impact with the antenna.
After an inspection of the P4 I put 4 new blades on it and turned everything on to see if anything worked. The battery still showed over 40%, and all indications were fine. After convincing myself the drone was, maybe, fine I launched it again and flew it, at low level, for a few minutes. There was no sign of abnormal operation.
On playback of the flight on my tablet I can see that at about the time the P4 shot up in altitude about 40 feet, without stick input form me, to about 220 feet on the data (if it can be believed). It then slid sideways (to the position over my truck) while visually rapidly descending on the video, and showing a slight descent in the data. On impact with the top of the truck, and the Motor Obstruction warning, the altitude in the data still shows about 120 feet above launch point. Obviously it could not be at 120 feet and still be putting those dents in my roof, but either the data is wrong or the World moved.
It might be worth noting the downwards collision sensors appear to have done nothing to stop the impact.
Further analysis of the flight data, both the DJIFlightRecord for that flight and the .DAT file data, seem to show that initially all was well, but about 77 seconds into the flight the GPS altitude data and the barometer altitude data started to diverge. The barometer data seems to slow and lag behind what the P4 was actually doing. For example at the time it impacted the top of my truck, and the first motor obstructed indication, the barometer altitude data showed the drone in a descent, but still over 35 meters above the top of the vehicle.
Since then I have had two more uneventful flights, showing no abnormal indications.
Have other people had similar failures?
T!
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