The death of an Air Force civilian contractor last year who walked into the moving propeller of a drone was due to the contractor losing situational awareness, according to the final accident investigation report. Investigators with Air Force Materiel Command also found that in the rush to complete testing supervisors skipped key parts of the safety briefing dealing with how to work around the aircraft when its engine was running.

The contractor, Stephanie Cosme, died on Sept. 7, 2023 while conducting telemetry readings on an MQ-9 drone at Gray Butte Airfield in California. The team of civilian contractors were working into the evening on ground tests on the drone when Cosme walked into the spinning propeller of the MQ-9, seriously injuring her. Crews and eventually emergency responders tried to help her. She was airlifted to a hospital but died soon after. She was 32. At the time, Cosme was working for Sumaria Systems LLC, a contractor hired by the Air Force.

The report from the Air Force Materiel Command Accident Investigation Board looked into the circumstances leading up to her death and what could have been done to prevent it. It found that the situation worsened due to a “clear lack of communication among the test team and ground support personnel,” the investigation found, as well as rushed efforts by the team. 

Cosme “was incorrectly instructed or trained on how to take telemetry readings when approaching the MQ-9A while the engine was running,” a statement from Air Force Material Command said. “Second, she lost situational awareness while walking around the mishap aircraft taking telemetry readings with a hand-held measurement device.”

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Cosme was conducting tests on a hand-held device, walking near the MQ-9 drone. While doing so, she got dangerously close to the aircraft and did not notice. Other members of the test crew noticed her walking toward danger and tried to wave her down, but were unable to reach her before she walked into the spinning propeller.

Ground crews were also rushing to complete their tests, following a Sept. 6 dry run. The mission and safety briefing on Sept. 7 skipped several steps, including important parts about emergency procedures and what the AIB called “aircraft keep out zones.”

As part of its investigation, the AIB staged a simulation of the conditions and layout at Gray Butte Airfield the night of the incident. Investigators found that “the spinning propeller was not visible when looking to the rear of the aircraft from the trailing edge of the right wing.”

Cosme is survived by her parents, two siblings, a fiance and a stepdaughter, according to her obituary shared on

“Throughout her life, Stephanie touched the hearts of everyone she encountered with her warmth, kindness, and unwavering love,” the obituary said. “She had an innate ability to make those around her feel special and valued. Her capacity to love and care others knew no bounds. Her gentle spirit and radiant smile brought comfort and joy to all who had the privilege of knowing her.”

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