OK, here's what happened.
This is a longer post, but wanted to follow up and share the loss, and eventual recovery, of my drone while it was on an autonomous mission using Litchi. Hopefully someone will find this helpful and reassuring.
In brief, I carefully planned the route online using the Litchi Mission Hub and used Google Maps and elevation charts to plan the waypoints. The flight was up a steep hillside to a fire road at the top of a ridge, which was at about the max altitude the Phantom can fly. (Note: the Phantom was always less than 300 feet over the ground at each waypoint). While I planned it for late afternoon/evening, it was nearly dark when I took off. I'm very familiar with the area though and planned to fly it up and back on a trail I regularly hike. The Litchi Mission Hub calculated the flight to be 2 miles and 11 minutes flight time. With such a steep climb, I left plenty of room for ascent and descent. All seemed good. (See below for mission plan with waypoints).
View attachment 43112
At the takeoff point, I did the usual startup procedure, setting up the camera using DJI Go. On takeoff, I turned on Litchi and once it was in the air sent it on its autonomous mission. It began heading off to the first waypoint.
Within a few minutes, I lost signal and got the big red "Disconnected" message at the top of the app. I knew the Phantom had the waypoints uploaded and that it would fly without being connected, and there was a hill blocking a direct clear path between me and the Phantom. I checked my watch and expected it home at around 11 minutes so I waited as patiently as I could, giving it a max of 20 before I went hiking.
After 10 minutes there was no sign of it. After 15 I was convinced something had gone wrong, so I grabbed my flashlight and started up the (steep) hill, controller in hand. I was hoping it would connect once I got within line-of-sight as long as I had some battery left. Just a few hundred yards up the hill, I looked to the west and high up in the sky (it looked like it was up at least 800 feet, maybe much higher - remember it's night time) and far away I spotted the drone's flashing lights - wayyyy up there. It appeared to be heading far past the takeoff point (and final mission waypoint) but I was hopeful it was on the way back. I quickly ran down the hill to the launch point, and tried frantically to reconnect with the Phantom. I restarted Litchi, tried DJI Go, and restarted the remote, all to no avail. While I was doing all of this I lost sight of the bird and assumed it ran out of battery and auto-landed in a heavily wooded area a long way distant. From where I last saw it in the air I knew it was long gone.
I came home and spent hours analyzing my mission plan, checked the waypoints carefully, and reviewing the software manuals. I could not figure out why it would fly the full mission and miss the last waypoint. Since it did go up the ridge 1600 feet, I figured it was still up at that altitude when it made the last pass overhead on the way back until in ran out of battery and landed itself miles away.
This morning I got a phone call - someone found the drone (with my phone number on it, which is the only reason I got it back). I was very surprised that someone could have found it in that forested area miles away that is also private property. Well, he didn't find it there. He found it on the hiking trail I was flying up. He said it was about 3/4 the way to the top of the ridge, and it was laying upside-down.
I downloaded the logs and video to figure out what happened. Since it was nighttime, the video didn't show much, but between the flight logs, the video I could see, and in reviewing the mission waypoints I found out what happened. In short, I ran into the hillside.
View attachment 43113
I set each waypoint altitude at least 150 feet above the ground level indicted by Google Maps, and most at 200 feet higher, just to be safe. Well, the hill isn't a smooth, even rise up to the top - there are outcroppings, ridges, trees, and valleys that rise above and drop below the elevation at each waypoint. While my altitude at waypoint 4 had plenty of ground clearance, I did not climb rapidly enough to clear a ridge between waypoints 4 and 5. The Phantom hit the ground and there she sat until it was found today. This also explains why I could not reconnect the controller to the Phantom when it was flying overhead – because it wasn't, in fact, flying overhead.
What about the phantom flying way up overhead past the final waypoint?
Obviously this was a misidentification on my part, in the "let's jump to conclusions" department. Since it was in the same area and roughly on the same heading I had plotted, I assumed it was my phantom. This is outside a major metro area and there are flights (far) overhead all the time, so that's likely what I spotted, and at night all I had were steadily moving lights way up there with no other points to reference. Given my set course and all that had taken place, I assumed it was my Phantom and that's what I immediately jumped to.
That's it. Again, this is long-winded and perhaps slightly embarrassing, but I think that's what communities like this are for - so we can all learn from each other. If anyone has any questions I'm glad to jump back in and answer.
And if you haven't done it already, post your phone number on the outside of your drone! That's the only reason I got it back and figured all of this out.
Thanks and fly safe.
