The United States’ National Transportation Safety Board (NTSB) has released its preliminary findings from an investigation into the crash of two Amazon drone delivery drones and a crane in Tolleson, Arizona earlier this month. There were no casualties.
The MK30 unmanned aircraft systems (UAS) were operating under a Federal Aviation Administration exemption on October 1.
The crane operator reported that the mobile crane arrived at the jobsite at 0530 and was erected between 0730 and 0800. At 0949, the crane operator felt something impact the erected crane that turned out to be a UAS. The crane operator terminated operations and was evaluating the UAS strike when a second UAS impacted the stationary crane. The crane was then retracted, lowered and inspected.
At the time of impact, the crane operator estimated that the crane was extended to a height of about 197.3 ft above ground level (agl) and at an angle of about 25°. The crane operator estimated the impact heights of the UAS as being between 150 – 165 ft agl.
The UAS operator reported that the UAS collided with the boom of a truck mounted mobile crane about 1.25 miles northeast of the departure location. The planned route of flight was at an altitude of about 200 ft agl. The operator told NTSB that normal operational procedures are for Ground Surveillance Crews (GSC) to conduct rooftop scans of the surrounding area twice per day, once in the morning and again about midday. On the day of the incident, GSC’s conducted their scans about 0658 and did not identify any obstructions that would have interrupted normal operations. The timings obtained by NTSB indicate that the crane was erected after the morning rooftop scan was complete.
Examination of the accident site revealed that the first UAS came to rest on the ground near the crane. The UAS battery had ejected and caught fire. Damage to the UAS fuselage and wings was observed. The UAS was recovered, and the flight data was downloaded.
“A review of the UAS flight track data showed that at 0924:40 the UAS activated and prepared for flight,” NTSB’s preliminary report states. “At 0947:10 the UAS ascended to about 1,043 ft mean sea level (msl) and conducted manoeuvres consistent with flight checks. At 0947:24 the UAS ascended to 1,154 ft msl then departed from the operator’s package delivery centre on a northern heading. At 0948:08 the UAS made a turn to the east while at an altitude of about 1,202 ft msl. The UAS remained on an easterly heading until the data stopped recording at 0949:03, at an altitude of 1,218 ft msl (about 200 ft agl), about 150 ft west of the crane’s location.”
NTSB has classified the incident as Class 3. Class 3 investigations seek to identify safety issues that reveal underlying cause(s) of the accident.
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Image: Amazon’s MK30 UAS (Amazon)
