What happened
On 17 April 2017, a Falcon 8 Trinity Asctec UAS was being operated for commercial inspection purposes from a vessel located in the North Sea. The mission began successfully, with the pilot performing standard hover checks at an altitude of roughly 20 m and a distance of 20 m from the ship. Following these checks, the pilot transitioned the aircraft into GPS mode, where it maintained a stable position.
As the pilot proceeded toward the intended task area, the aircraft reached a distance of approximately 30 m from the ship when it unexpectedly entered its 'Come Home High' emergency mode. This mode was triggered by a loss of link between the aircraft and the ground station. The pilot attempted to intervene by switching the flight mode to height mode and subsequently to manual mode, but these actions failed to restore control. The UAV descended into the sea, where it remained afloat briefly before sinking. The operator managed to recover the aircraft back to the ship.
The investigation
Following the incident, the aircraft was sent to the manufacturer to undergo technical analysis. Investigators examined the software, the UAV itself, and the ground control station to determine why the command link had been severed. However, these diagnostic tests failed to reveal any specific hardware or software faults.