In October, the US National Transportation Safety Board (NTSB) updated its Aviation Accident Preliminary Report on the June 4 crash of the Aurora Flight Sciences “Pegasus” Passenger Air Vehicle (PAV) demonstrator. The unmanned aircraft (N83AU), sized for two seats, was destroyed on its fifth flight. According to the report, “The normal landing maneuver for the PAV was an autoland, which establishes a vertical descent and transitions to on-ground mode using a combination of squat switches and a time derivative of acceleration known as ‘jerk’ logic. When the aircraft contacts the ground and either the squat switches close or an acceleration spike is detected, the logic switches to ground mode and commands the VTOL motors to idle.” The report concluded that “airframe vibration occurred in a resonant mode and was transmitted through the structure into the flight controller. The accelerations resulting from the vibrations briefly exceeded the jerk logic threshold and the aircraft entered the ground mode, subsequently commanding the motors to shutdown.” The second Pegasus is expected to being flying in early 2020.

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