Primary finding
Probable cause
An improper altitude indication from a recent software update, which resulted in a loss of engine power in flight.
Investigator assessment
Analysis narrative
The operator of the unmanned aircraft system (UAS) reported that, during a test flight with a new software upgrade, the UAS completed the delivery mission and was transitioning to land, when all six motors suddenly stopped. The UAS fell to the ground and impacted the asphalt taxiway, resulting in substantial damage to the fuselage and wings. Examination of the UAS by the operator revealed that the vehicle erroneously determined it had touched down due to an incorrect altitude reading from a new software installation, which resulted in a loss of engine power. The operator reported that there were no preaccident mechanical failures or malfunctions with the UAS that would have precluded normal operation.