Risk Analysis for Level 4 Drone Maneuvering: Safety in GPS Signal Loss

“The Roadmap for the Application and Technology Development of UAVs in Japan” classifies the flight operations of unmanned aerial vehicles (UAVs), more popularly known as drones, into four levels, the highest of which is “beyond visual line of sight operations without assistants in populated areas.” This study performed a risk assessment of Level 4 flight operations. Using failure mode and effects analysis, we identified the loss of the global positioning system (GPS) signal as an important failure mode. When the GPS signal is lost, drones are often designed to enter the ATTI (attitude) mode, a manual control mode, but this mode supports only altitude maintenance and is susceptible to environmental factors. We conducted an experiment using a drone flight simulator to observe the behavior of operators when the GPS signal was lost and examined possible risk factors to propose countermeasures. The participants (N = 21) performed five scenarios of delivery tasks around Akihabara Station, with the location of the GPS signal loss changing in each scenario. By analyzing the results of behavioral observations and interviews, we found that the behavioral patterns differed based on the information used by the participants, and they made decisions regarding the relationship between the distance to the destination and distance to the emergency landing points, among other options.