The National Transportation Safety Board said that decision, along with pilot James Freudenberg's failure to perform a crucial flight maneuver after his engine flamed out, was the probable cause of the crash.
"This accident, like so many others we've investigated, comes down to one of the most crucial and time-honored aspects of safe flight: good decision making," NTSB Chairman Deborah A.P. Hersman said in a release.
The NTSB investigation also found the pilot had made and received multiple personal calls and text messages throughout the afternoon while the helicopter was being inspected and prepared for flight and while flying.
The board said there was no evidence the pilot was using his cellphone when the helicopter lost power, but called the texting and calls a source of distraction that likely contributed to errors and poor decision-making.
"This investigation highlighted what is a growing concern across transportation -- distraction and the myth of multitasking," Hersman said. "When operating heavy machinery, whether it's a personal vehicle or an emergency medical services helicopter, the focus must be on the task at hand: safe transportation."
The NTSB cited four contributing factors: distracted attention due to texting, fatigue, the operator's lack of policy requiring that a flight operations specialist be notified of abnormal fuel situations, and the lack of realistic training for the emergency maneuver that could have allowed the helicopter to land safely.
The NTSB made nine safety recommendations to the Federal Aviation Administration and Air Methods Corp., and reiterated three previously issued recommendations to the FAA.
The Eurocopter AS350 B2 helicopter, operated by Air Methods of St. Joseph, was on a medical evacuation assignment to take a patient from a hospital in Bethany to a hospital 62 miles away in Liberty when it went down a mile from an airport in Mosby. Besides Freudenberg, the victims included paramedic Chris Frakes, nurse Randy Bever and a 58-year-old female patient, OzarksFirst.com reported at the time. The news website said Freudenberg had not been with the company long but had previously flown for the military.
The NTSB said less than 10 minutes after leaving its base, the pilot radioed he had 2 hours of fuel on board. After picking up the patient, he indicated he actually had about half the amount of fuel initially reported and would need more to complete the next flight leg to the destination hospital.
The NTSB said even though the helicopter had only about 30 minutes of fuel remaining and the closest fueling station along the flight route was at an airport about that far away, the pilot elected to go on. He departed the first hospital and the aircraft ran out of fuel within sight of the airport.
The NTSB said the helicopter crashed after the pilot failed to execute what is called autorotation, an emergency flight maneuver that must be performed within about 2 seconds of the loss of engine power in order to landing safely.
Investigators determined the autorotation training the pilot had received was not representative of an actual engine failure at cruise speed, which likely contributed to his failure to perform it properly.
The NTSB said a lack of specific guidance in FAA training materials means many other helicopter pilots also may be unaware of the specific actions required within seconds of losing engine power. The board recommended the FAA revise its training materials to bring pilots up to speed on the maneuver.