Lost Link - Do You Know Where the Drone is Going?

Let’s say you’ve been hired to fly a solar farm in a semi urban area that requires airspace authorization. You have been authorized to fly up to 200ft which is perfect since the mission only requires you to go up to 120ft. Once on site, you complete all your pre-flight checks and begin the mission, everything is going smoothly, and you are monitoring the drone’s progress as it zips through the air.

As you’re watching the drone you notice it has stopped and is hovering. You look down at the controller and see the video feed is grayed out. Wait. The controller has lost connection to the drone. Do you know what your drone is going to do in this scenario? ?

For many, the answer would be a general, “it’s going to return to home.” But do you know the how it will return to home? Many operators will leave the RTH set to the default parameters and never think to look at them, but this can be a fatal mistake. In the scenario from before, the operator knew the drone would return to home, but did not know the how, and failed to set the proper settings for the operation. Because of this, the drone went on its configured lost link procedure and climbed to 400ft and broke the airspace authorization. While the drone returned safely without issue the operator got to have a fun phone call with Air Traffic Control and the FAA and was unable to complete the job.

107.19 requires that before every flight the “the remote pilot in command must ensure that the small unmanned aircraft will pose no undue hazard to other people, other aircraft, or other property in the event of a loss of control of the small unmanned aircraft for any reason.” A major part of meeting that requirement is first understanding the systems our aircraft are equipped with in the event of an emergency. Going through your drone’s manual is a great way to familiarize yourself with the features of the system.

In general, there are primarily two responses that drones will do in a lost link scenario, hover, or return to home. Each of these options should be fully understood as to what the drone will do and when you want to select each.

Starting with hover mode, this one if pretty self-explanatory, although there are some surprises that will trip up even the most experienced operator. When selected, the drone will stop in place and wait until it re-establishes communications. This should be used when in closed off or rural areas as you don’t want a bystander to walk under the drone when you are unable to move it. It can be beneficial when on a long mission that you may night be able to resume if the mission gets disrupted.

The tricky part with hover is that you will eventually hit another contingency plan, low battery mode. If the drone hovers for long enough and doesn’t reestablish communication, the low battery mode will step in, creating the potential for additional issues if those settings have not been carefully set up as well. This is where even experienced pilots can get in trouble as on some drones the return to home height for lost link is a different setting to low battery. The other common option for low battery is to immediately land. Imagine if you were the pilot from the scenario in the beginning, instead of the drone returning home it hovers for a while and then lands on top of a solar panel! ?

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We’ve already discussed return to home mode, but it is crucial to know how your specific aircraft is going to return. Is it going to climb to a minimum safe height first or will it fly directly back to the home point? Many newer drones use obstacle avoidance as a supplement to the RTH feature. This can be beneficial to have turned on, however, keep in mind that they will usually return slower than with it turned off. One additional thing to think about is if the drone will be able to return. There are many different operations that the drone might fly away from the takeoff location and not be expected to return. In these cases, the drone could lose power before making it back to the home point resulting in an unexpected landing.

Having a detailed understanding of your specific drone is crucial to pilot professionalism and will undoubtedly help you be ready for an emergency when they arise.