What happened
On March 25, 2010, at approximately 0600 CDT, a Eurocopter AS350 B3 helicopter, registration N855HW, impacted terrain near Brownsville, Tennessee. The flight was being operated by Memphis Medical Center Air Ambulance Service as a positioning flight under 14 CFR Part 91. The aircraft was traveling from Jackson-Madison County General Hospital Heliport (TN05) to Haywood County EMS Heliport (99TN).
Prior to the accident, the pilot had completed a patient transport from Parsons, Tennessee, to the hospital helipad at TN05. During this time, the pilot spoke via cellular telephone with an oncoming pilot at the home base. The two discussed an approaching weather system, and the accident pilot expressed a desire to "get the helicopter out" to beat the storm, estimating he had about 18 minutes before the weather arrived. Although the pilot initially intended to leave the flight nurses behind and return alone, the crew members had actually boarded the aircraft and were nearing the base at the time of the impact.
At the time of the accident, the area was experiencing a mesoscale convective system characterized by a bow echo, which brought localized instrument meteorological conditions (IMC), heavy rain, lightning, and wind gusts. The helicopter struck the ground in an open wheat field approximately 2.5 miles east of its home base. The crash resulted in 3 fatal injuries.
The investigation
Investigators examined the wreckage and found no evidence of preimpact mechanical failures or malfunctions in the engine, drive train, main rotor, tail rotor, or helicopter structure. There was also no evidence of an in-flight fire. The engine showed evidence of power at the time of impact, including foreign object damage to several compressor blades.
Analysis of the aircraft's multifunction displays and weather data revealed that the pilot was receiving NEXRAD weather updates, though there is inherent latency in such systems. Radar imagery confirmed that the aircraft likely encountered the leading edge of a thunderstorm line. The investigation also looked into the pilot's fatigue levels, noting he was nearing the end of a 12-hour duty shift and working an overnight period, though the specific impact of fatigue on decision-making could not be definitively determined.
Findings
- The pilot made a risky decision to attempt to outrun an approaching storm during night operations rather than choosing a safer alternative, such as parking the aircraft or waiting for improved conditions.
- The helicopter encountered a thunderstorm featuring heavy rain, lightning, and severe turbulence.
- The encounter with severe turbulence at a low altitude left no possibility for recovery.
- The pilot was aware of the approaching adverse weather but chose to proceed with the flight into the area.