Understanding the DJI Return to Home Failsafe
The DJI Return to Home failsafe is a wonderful safety feature. When it is activated your drone to fly itself back to the take off location and land itself. But if you don’t understand it works or don’t have it set properly you could end up having a very bad day. By that I mean crashing your drone.
There are actually three types of Return to Home:
Low Battery Return to Home
The DJI GO4 app constantly monitors the battery charge levels and warns you when it reaches certain thresholds. If you ignore the warnings and keep flying, the battery eventually reaches a critical level and the controller will give you a stern rebuke for ignoring its earlier warnings. Then it will give you a 10-second countdown after which it will initiate the Low Battery RTH. If the controller determines there is not enough power left to get the drone all the way back to the home point, it will automatically land the drone rather than have it just fall out of the sky. Once this auto landing starts, you can’t stop it. What you can do is take a quick look and the map to see the drone's location. You can also tilt the camera down to see what the landing spot looks like. With any luck it will land in a safe spot and you can retrieve it.
Failsafe Return to Home
If your drone loses its radio connection to the controller for three seconds it will initiate the whatever actions you have set up in the DJI GO4 preferences. The default setting is to ascend to a pre-set altitude and head directly for the home point. Another option is to have the drone go into hover mode until it either re-acquires the signal or runs out of battery and auto lands. The third option is to set it to land wherever it is as soon as it loses signal.
Smart Return to Home
If you lose sight of your drone or lose orientation and can’t tell which direction it heading, you can press the Return to Home button on your controller or tap the RTH icon on the app. Your drone will go to the altitude you have set in the preferences and head straight back to you. The one exception is if it is less than 20 meters away when you press the button, in which case it will just land wherever it is. That could be risky, so I would recommend if the drone is that close, just fly it home manually.
Problem With Return to Home
The problem is not with the Return to Home feature itself . Most problems with RTH are a result of not understanding how it works or not thinking through what is going to happen if it is triggered.
You are flying in a downtown area and have skillfully piloted your drone around the buildings. But then it goes behind an office tower and loses signal. You’re not worried because you know the Failsafe RTH will kick in. Sure enough, you hear your controller telling you your baby is on its way home. You look down at your screen just in time to see it plow head first into the side of the office tower. Then you remember that you have your Return to Home altitude set at 20 meters. That’s plenty high for where you usually fly but not nearly high enough for your current location.
You are flying in the mountains. You take off from the bottom a ravine and fly down a creek for a ways. Then you head up the side of the ravine to the top of the ridge line several hundred feet above you. Your drone is getting pretty far away and you’ve lost track of its orientation, so you just hit the Return to Home button. The trees are pretty tall, but you know you have the Return to Home altitude set at 60 meters, so you’re not worried about clearing them. But when you look at your screen you see that your drone is descending, not ascending, and is getting ready to hang itself in the top of a tree. Your mistake was not realizing that the Return to Home altitude is based on the home point not its location when you signal it to return home.
Sometimes it’s not crashing into obstacles that causes problems, it’s where your drone lands. A lot of people fly drones from boats. That’s fine, just remember that if one of the Return to Home modes gets triggered, the home point is the spot where your boat was when the drone took off, not where your boat is now. If you don’t catch it in time and cancel the RTH, your drone will go swimming. Here’s a tip that may save you a drowned drone someday. Before you take off, set your homeport to somewhere on the shore. That way you always have a safe place to land if you need to.
Use Correct Settings to Avoid Problems
It is absolutely critical that before you take off you check to be sure the RTH altitude is set high enough for your drone to safely clear any obstacles as it is flying back. Here’s how you do it:
Connect your phone or tablet to your Controller. Launch the DJI GO4 App, power up the controller, then power up the drone. Tap the Controller icon a the top of the screen to open the Main Controller Settings screen.
Now tap on the box in the top right and enter the altitude you want the drone to climb to before it starts heading to the home point. Be generous, trees are often higher than your think. For some reason, this number is in Meters, even if you have your preference set to use Feet. I keep mine set at 30 meters, but adjust it higher or lower if needed.