What happened
On March 12, 2015, a Eurocopter AS350 B2 helicopter, registration N919EM, crashed into trees and terrain near Eufaula, Oklahoma. The flight was an emergency medical services (EMS) positioning flight operated by Eagle Med, LLC, traveling from St. Francis Hospital Heliport in Tulsa to McAlester Regional Airport.
Prior to the flight, the crew had checked weather reports indicating high ceilings and good visibility. Although the pilot had noted lower-than-expected clouds during a previous flight that day, the crew decided to proceed with the return flight after re-checking the weather on the ground. During the southbound cruise at approximately 1,50 and 1,500 feet mean sea level, the aircraft unexpectedly entered instrument meteorological conditions (IMC).
According to the medical crewmembers, the pilot attempted to divert to another airport after seeing lights to the left. During a left turn, the crew observed trees and issued a "pull up" command, but the helicopter struck trees and terrain atop a wooded hill. The impact resulted in the separation of the tailboom and significant damage to the fuselage.
The investigation
Investigators examined the wreckage and found that the engine, transmission, and flight controls showed no preimpact anomalies. The aircraft's GPS transmitter had sent 39 messages to the company, with the final messages showing the helicopter descending to altitudes between 380 and 414 feet before the accident.
A recent FAA ramp inspection of the operator's facility had identified discrepancies with the radio altimeter indicator and the night vision goggle (NVG) lighting system; both had been deferred for repair.
Toxicology testing performed on the pilot's specimens detected zolpidem, a prescription hypnotic medication used for insomnia, in the blood and liver.
Findings
- The pilot experienced spatial disorientation during a turn following an inadvertent encounter with night IMC.
- The aircraft descended into trees and terrain due to this disorientation.
- The pilot's blood and liver contained zolpidem, which can impair the mental or physical abilities required to operate heavy machinery.