Return to home: Confessions of a novice drone pilot


There is no panic quite like that experienced by a child who knows he’s about to lose his favorite toy. Today I proved that fact is true of adults, too.

My heart rate has returned to normal, I’ve stopped shaking, tears are wiped away, and, man, did I learn my lesson! Okay, maybe there’s a little bit of hyperbole in that sentence. In any case, I’ve calmed down.

My wife gave me a drone for Christmas, a DJI Mini 2 SE. It’s a lot of fun to fly. A smart phone attaches to the controller, and the drone sends continuous live video to the phone, so the pilot sees what the drone sees. The drone camera is excellent. The lens is mounted on a gimbal, providing the opportunity to see what is directly ahead of the craft, or directly below it, and everything in between. The camera can take high quality stills or videos. I hope to use my drone to shoot pictures and videos of railroad trains from above, including the R. J. Corman operations here in Greenville. However, this morning, I came very close to losing the aircraft due to my own stupidity.

I wanted some footage of Greenville’s Municipal building, the fountain in the circle, and the Darke County Courthouse, as well as some of the old, stately buildings dotting South Broadway. Had about nine minutes of battery left when the drone took off. Figured that would be plenty.

Um, no.

Flying high over the tall buildings on South Broadway, I wasn’t paying attention to the battery level in the drone and ran it down to about zero. When the controller issued a verbal warning, “battery power low” it caught me completely off guard. If it ran out of juice before I could land it, there were a lot of four- and five-story roofs it could come down on, never to be retrieved. I looked up to locate the drone and fly it back to me—but I could not spot it anywhere, and the battery level was dropping. I began to panic.

The drone has excellent software, including a “return to home” (RTH) emergency routine that kicks in when the battery level falls to a certain point. The RTH function requires the “home point” of the drone to be set before takeoff, and it is set based on signals from the network of global positioning satellites (GPS) overhead. However, the GPS capability is limited. It does not fix the drone’s position in an exact bullseye, but in a circle about six or eight feet in diameter. Anywhere within that circle is counted as the home point.

For the RTH function to execute safely, the drone must be informed by the pilot as to the height of the tallest surrounding objects. This is necessary so that the drone does not collide with anything when returning to home on autopilot. When the RTH emergency function kicks in, the drone first climbs to the programmed altitude (a necessary but counter intuitive move when the battery is low) before it zooms back to the home point. Once it returns over the home point, the drone descends and lands. At least, that’s how it supposed to work. The automated RTH function is a very reliable capability, as long as the pilot of the drone observes some common sense rules.

Which I did not. I made two mistakes. First, I set the tallest object to 400 feet—the maximum altitude for legal flying. This was probably two hundred feet higher than it needed to be on South Broadway. Not good, when the emergency is your diminishing battery power. The aircraft has to waste energy climbing two hundred feet more than is necessary.

My second mistake was setting the drone’s home point too close to the building I was next to. That eight-foot circle describing the home point could have brought the aircraft down on a roof five-stories up. A gust of wind—anything—could have set the drone down on an unreachable roof, and my new favorite toy would be gone forever.

When the controller notified me that the automated RTH function was being enabled, I suddenly realized my mistakes. So I panicked. I just knew that RTH function would land my drone on a roof—and I’d never see it again. I decided to override the RTH function and land the thing myself. But looking up, I couldn’t spot it anywhere (which was my third mistake—you’re supposed to keep the thing in visual range at all times). I couldn’t guide it back to me, because I couldn’t see it. By now I was equally afraid the propellers would just quit and the drone would just fall out of the sky. With my luck it would probably clonk someone on the head (in actual fact, this cannot happen—when the battery level drops to a certain point, the drone begins a controlled descent that cannot be overridden by the pilot and gently lands wherever it finds itself—including on a roof)!

By now, I simply wanted to get the silly thing on the ground without hurting anyone. Any port in a storm, right? I overrode the RTH function and gimbled the camera so it was looking straight down, and then positioned the drone over a sidewalk. I descended rapidly, making corrections when it strayed over a roof and finally landed it in the middle of a sidewalk.

Which sidewalk? Beats me! I was focusing on landing it safely, didn’t pay attention to where in Greenville it was landing. I began to search, convinced that some passerby was accidentally going to step on my toy and squash it, or pick it up and run off with it.

By now you have discerned that I am an idiot. Okay, I’ll own the moniker, and even prove it to you: the drone controller has a function, “where’s my drone?” It’s designed for precisely the situation I was in: looking for a drone that landed who-knows-where.

It never even occurred to me to use the “where’s my drone” capability (Hey—I’m new at this, okay?). Instead, I started watching the video signal, which the drone was still transmitting to the controller. It was showing me cars that were passing by. Getting my nose out of the controller, I looked up and began looking for the cars that had just passed the drone, and finally found the silly thing.


What I learned (after I calmed down): (1) Program the drone properly with the max height of surrounding objects before takeoff; (2) Do not set the home point close to a building or a tree (I’m going to make sure I am at least twelve feet from any object); (3) Never, never, never run the battery down to where the RTH automated function kicks in; (4) keep the drone in visual range.

Earlier in the morning, on a separate flight (with a fresh battery!), I did capture the footage I was after.

You can get a brief (just over four minutes) birds-eye view of South Broadway here.