Accident Summary
On March 14, 2023, at approximately 1030 central daylight time, a Bell Textron APT70 unmanned aircraft, registration N314AL, was substantially damaged in an accident near Mineral Wells, Texas. The aircraft was being operated under Title 14 Code of Federal Regulations Part 91 as a flight test.
Sequence of Events
During the flight test, the aircraft returned to base and entered a transition to hover. The flight control computer registered a low battery voltage reading and initiated an emergency automatic land in place flight command. The ground safety officer (GSO) attempted to override the system, but the system rejected the commands. The crew then observed the “F BATT CRIT LOW VOLT” warning, which triggered a descent for the aircraft to land at its current position. At that time, the aircraft was in a hover at an altitude of about 100 feet above ground level over a large bush. The Land Failsafe command was activated. A command was sent to override the landing command, but the ground control station indicated the override was rejected. The GSO then attempted to change the land in place waypoint, but the system again rejected the command. The aircraft performed the land in place maneuver and collided with a shrub, causing the aircraft to tip over and come to rest inverted.
Damage
The accident resulted in substantial damage to the lower left wing section.
Post-Accident Findings
The operator reviewed the aircraft systems and determined that the low voltage threshold was overly restrictive. Additionally, a software limitation prevented the crew from overriding the land in place command by changing a waypoint.