Government UAS pilot reported a lost link during a training flight. The UAS initiated an automatic RTH and landed.

Narrative

Person A conducted a Small Unmanned Aircraft System (sUAS) Pilot Flight Evaluation using corporate-owned asset; a Skydio S2. Person B and Person C served as sUAS Technicians (trainees); while Person D acted as the sUAS Check Pilot. Person E served as the sUAS Technician; and Person F served as the Flight Release Officer. The evaluation took place at Location X The UAS Organizational Risk Management Matrix score was 19 (low risk). Flight release was approved. A pre-flight inspection was completed using the sUAS Checklist. Battery 17-BATT-4 was installed and measured 99 percent charge at takeoff at XA23L. Person A began the flight by performing half-stick maneuvers and system checks; all of which were normal. The aircraft then ascended to 25 feet AGL and executed straight-and-level; square-pattern; and point-of-interest maneuvers. Approximately four minutes into the flight; Person A handed the controller to Person D so she could reposition the aircraft to an area suitable for the recovery-from-unusual-attitude maneuver. About 90 seconds later; the iPad display went black while the battery remained at 78 percent. Person D announced 'Lost link' three times at XA28L; five minutes into the sortie. The sUAS automatically ascended to between 100 and 150 feet AGL. At that moment; the Pilot in Command's position was Location Y; and the sUAS position was Location Z; a distance of approximately 120 feet. The PIC attempted to manually return the aircraft to the home point but was unable to control ascent or descent functions. The aircraft autonomously initiated return-to-home and descended over the landing area while the iPad screen remained blank. After cycling the iPad's power; the display returned; but connection to the sUAS could not be re-established. The sUAS hovered over the home point at roughly 5 feet AGL; then gradually descended to 2 feet AGL and self-landed after approximately 90 seconds. Video recording stopped at 6 minutes 12 seconds; and total flight time was 7 minutes (0.08 hours). The battery charge prior to the lost link event was 78 percent. Post-flight observations noted that the iPad had 83 percent battery at XD16L; while sUAS Battery 17-BATT-4 measured 56 percent at XD19L. The iPad displayed a 'storage full' warning; indicating low available memory. No equipment damage or personnel injury occurred during this sortie.