UAS crew reported during a test flight the UAS departed its preprogrammed path and ascended above 400 ft. The UAS crew took manual control of the UAS and initiated a return to home.

Narrative

Our research team was flying at Location X. Our hex-copter uses the Px4 stack with a Jetson NX onboard. Our own software which we have used on numerous missions was installed on the Jetson. A mission was sent from our Ground Station to the Jetson and the drone then configured itself for the mission. In this case the mission was simple (e.g.; arm; takeoff; fly to some waypoints; return home). The operator who launched the mission from the Ground Control station; monitored the mission using QGroundControl. We had planned a route for our hex-copter to go out over the farmland along a route that we had tested in the simulator and previously flown successfully. We set a circular geofence; however we accidentally did not set a geo_fence action. The route intersected the geofence at the southwest corner and this is where the incident was triggered. As the Visual Observer (VO); I maintained VLOS throughout the entire mission and held a Radio Controller for use in an emergency. After hitting the geofence; the drone flew due north (which was not part of our planned route). It also ascended rapidly. Although I didn't realize it at the time; it ascended to 774 ft. The planned mission should have completed at a maximum altitude of 130 ft. After realizing that the drone had departed from its planned route; I assumed manual control by using the handheld RC to issue a Return To Land (RTL) command. The drone responded immediately and started its return to its home coordinates where it landed safely. The drone remained within the circular geofence at all times; however; it exceeded the Part 107 allowed altitude of 400 ft. AGL.To ensure that a similar incident does not occur; we have instituted several changes in our procedure as follows: Prior to each mission we will set a perimeter geofence and a corresponding geofence action. We will also set an upper altitude geofence to prevent flights above 400 ft. AGL. The operator at the ground control station will be trained to monitor for altitude; the VO will check for altitude on our RC screen if the drone appears to fly too high.In addition; we are figuring out why this situation occurred. Even though we believe it is preventable with a proper geofence_action set in Px4; we are also investigating why the drone flew too high and in the wrong direction after the geofence breach. We will make any adjustments needed and then run controlled tests to validate that the problem is properly resolved.