A United States Air Force investigation into the death of an army contractor who walked into a spinning aircraft propeller concluded poor lighting conditions and inadequate briefing were the main causes of the accident.
At around 8 p.m. on Sept. 7, 2023, instrumentation engineer Stephanie Rachel Rodriguez Cosme, employed by army contractor Sumaria Systems, suffered critical injuries while taking telemetry readings around an MQ-9A drone aircraft at Gray Butte Field Airport in California.
According to the Air Force investigation report, Ms. Cosme “inadvertently walked into the parked remotely piloted aircraft’s rotating propeller.”
She died shortly after being airlifted to Antelope Valley Hospital in Lancaster. Ms. Cosme was 32 and engaged.
Accident Investigation Board (AIB) president Brig. Gen. Lance R. French concluded that Ms. Cosme had been “incorrectly instructed or trained on how to take telemetry readings when approaching the MQ-9A while the engine was running.”
The AIB found no evidence that Ms. Cosme was instructed on all mandated procedures. The investigation also mentioned that she had limited experience working with propeller-driven aircraft.
“It was noted that [Ms. Cosme] kept referring to the MQ-9A as a ‘jet’ vice a ‘plane’ like other personnel,” the report read.
“Second, she lost situational awareness while walking around the mishap aircraft taking telemetry readings with a hand-held measurement device,” Mr. French said.
The AIB replicated the accident in near-identical conditions: with an MQ-9 drone parked in the same spot, with the engine running at the same power setting, and in similar twilight—near-dark—lighting conditions with identical airfield lighting present on the day of the accident.
The simulation revealed that under those lighting conditions, the spinning propeller was not visible from where Ms. Cosme had approached the aircraft.
The AIB noted that Ms. Cosme was holding an unfamiliar measuring device that blacks out automatically every 60 seconds and believes that her fixation on the instrument may have distracted her, despite that she likely must have felt the vibrations of the propeller, which was running at maximum speed at the time of the test.
“She continued to look down, fixated on the testing device,” the report read.
The report also noted that Ms. Cosme was not equipped with any communication device while doing the measurements.
According to Mr. French, there was “a clear lack of communication” not only among the Sumaria Systems test team itself but also with other ground support personnel—none of which were military staff.
“The mishap contract employee, aircraft crew chief and maintainers, as well as the test director, mishap pilot and sensor operator in the nearby ground station, were civilian contractors,” Mr. French said.
He furthermore stated that the tests conducted that day “were rushed” owing to previous delays and cancelations.
According to her family, Ms. Cosme was a gentle spirit with a passion for crafting, baking, aviation, and “all things strange and unusual.”
Gray Butte Field Airport, where the accident took place, is owned and operated by General Atomics and is located near Edwards Air Force Base in Kern County, Southern California. The facility is primarily used for the development and testing of Unmanned Aerial Vehicles for the U.S. Military and government.
