The fatal Sept. 8, 2017 crash of an Airbus BK117C2 helicopter air ambulance occurred after the pilot shut down the number-one engine after the number-two engine began to fail, according to an NTSB final report. “The complete loss of engine power likely occurred at an altitude and/or airspeed that was too low for the pilot to execute a successful emergency autorotative landing,” it added.
Operated by Air Methods, N146DU crashed near Hertford, North Carolina, at 11:20 a.m. local time en route to the Duke University Medical Center, killing all aboard—the pilot, both flight nurses, and patient.
Eyewitnesses reported that the helicopter was trailing thick, dark smoke befoe an impact described as “straight down.” The NTSB investigation found that while the number-two “engine experienced a bearing seizure; the engine continued to run” for a brief period before losing all power and that “neither engine exhibited damage consistent with rotation at time of impact.”
An NTSB review of maintenance records found that oil tests on the number-two engine in the nine months before the accident revealed that “metallic contaminants” detected in it, while within manufacturer specifications, were at levels “considerably higher” than the other engine. Further, “The oil test evaluation procedures did not include steps to monitor trends of contaminant concentration levels over time. If the engine manufacturer’s procedures had included appropriate trend monitoring criteria, the impending bearing failure in the No. 2 engine might have been detected and mitigated.”