Beeville, TX, USA
N243XT
BOEING CV2
Same as Factual Information
On June 21, 2019, at 0842 central daylight time (CDT), N243XT a Boeing CV2-Cargo Air Vehicle (CAV), unmanned aircraft system (UAS), sustained substantial damage during a contingency landing during a test flight at Chase Industrial airport (TX2), Beeville, TX. This aircraft is a large UAS with 12 electric motors and 12 propellers mounted in the horizontal or near-horizontal plane. It is a developmental platform for unmanned cargo operations. The pilot does not control the flight path, speed or attitude of the aircraft in flight, all flights are preprogrammed. The only ability the pilot or ground control station operator has to affect the flight is through contingency management via the "abort to planned zone" (APZ), "land now" or "cut power" (terminate the flight) commands. Flight testing of the aircraft had been going on for several weeks, with approximately 45 flights completed. Test flights were very short in duration, no longer than 4 minutes. According to the manufacturer/operator, the accident flight was a planned 30 knot flight over the grass area between the runway and the taxiway. All preparations for the flight were normal. After takeoff and turning on course to parallel the runway/taxiway, the aircraft started to deviate from the programmed flight profile. The flight test area included a two-level geo-fence boundary to keep the aircraft contained within a safe area. The aircraft identified the deviation and autonomously triggered an "abort to planned zone" (APZ). The APZ is a contingency plan where the aircraft stops the current flight and immediately turns towards the closest planned landing zone (in this case, the taxiway) and begins the approach. However, the aircraft continued the lateral deviation. The aircraft reached the first geo-fence boundary and then autonomously executed a "land now" command where the aircraft immediately begins a landing regardless of its position. The aircraft appeared to adjust pitch attitude for the abort to planned zone landing and drifted towards the second geo-fence boundary. Upon reaching the outer geo-fence, the aircraft autonomously cut power to all motors and dropped to the ground, as designed. The aircraft was substantially damaged, there were no injuries. The aircraft remained within the test area. A review of the flight data by the manufacturer/operator revealed that the lateral deviation initiated due to higher than expected and accounted for wind, which resulted in high vibration within the aircraft navigation system. The contingency logic was unable to return the aircraft to the planned abort zone prior to reaching the outer geo-fence. The manufacturer/operator determined that there had been insufficient tests related to high crosswinds, and insufficient ability to determine winds during test flights. Additionally, the manufacturer/operator determined that the physical separation between the abort to planned zone (APZ) and geo-fence locations was inadequate for the aircraft to maneuver considering the wind and other environmental factors.
A higher than expected and accounted for crosswind which initiated a lateral deviation, and resulted in the aircraft reaching the limits of the geo-fence area triggering a contingency forced landing.
Source: NTSB Aviation Accident Database
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