History of Flight
On February 15, 2012, about 1301 mountain standard time, a Bell Helicopter model 407, registration N407HL, was substantially damaged when it impacted trees and terrain in the Bridger Teton National Forest near Moran Junction, Wyoming, during a search and rescue (SAR) mission. The commercial pilot and one SAR crewmember received serious injuries, and the other SAR crewmember received fatal injuries. The public-use flight was operated by the Teton County Sheriff's Office (TCSO). Visual meteorological conditions prevailed, and no Federal Aviation Administration (FAA) flight plan was filed for the flight.
The mission was in response to a reported snowmobile injury accident, in order to transport medical personnel to that scene. Initial attempts to locate that victim, based on trail network and geographic coordinate information, were unsuccessful. The helicopter began a search, and the crew observed two snowmobilers signaling to them in a meadow. The helicopter landed in the meadow, and a SAR member exited and spoke with the snowmobilers. They were from the victim's party, and they agreed to lead the helicopter on their snowmobiles to the accident site. The SAR member re-boarded the helicopter, the helicopter lifted off to follow the snowmobilers, flying about 100 to 200 feet above the trees. Since the helicopter was faster than the snowmobiles, the pilot stopped two or three times in a hover to allow the snowmobiles to catch up. On either the second or third hover, the pilot experienced a slight left yaw, which he believed he corrected. The helicopter then started "spinning rapidly" and descended into the trees. The pilot and the surviving SAR member both believed that the spin direction was nose left, but they were not certain.
The SAR member in the rear seat remained conscious throughout the event, extricated himself, despite an injured leg. He assisted the other SAR member and the pilot out of the helicopter after they became verbally responsive. The pilot carried a radio to the top of a nearby ridge and requested assistance. Reports varied as to when the first ground personnel who were originally responding to the snowmobile accident arrived at the helicopter, but the first TCSO personnel reached the helicopter about 1622.
Personnel Information
Federal Aviation Administration (FAA) information indicated that the pilot held multiple certificates and ratings, including a commercial pilot certificate with a rotorcraft-helicopter rating. The pilot reported a total flight experience of about 22,250 hours, including about 4,500 hours in the accident helicopter make and model. His most recent FAA second-class medical certificate was issued in May 2011. He was the chief pilot for Hillsboro Aviation, Hillsboro, Oregon.
Aircraft Information
According to FAA information, the helicopter was manufactured in 2008 and was equipped with a Rolls Royce 250-C47 series turboshaft engine. The helicopter was registered to Hillsboro Aviation, leased to TCSO, and operated by Hillsboro flight personnel. At the time of the accident, the helicopter had accumulated a total time in service of 828.6 hours. The operator cited the maximum allowable gross weight of the helicopter as 5,250 pounds, which agreed with the FAA type certificate value when the helicopter was equipped with kit 407-706-020.
Meteorological Information
The 1251 automated weather observation for the departure location, Jackson Hole Airport (JAC), Jackson, Wyoming, located about 25 miles southwest of the accident site, included winds from 090 degrees at 4 knots, visibility 10 miles, few clouds at 4,500 feet, temperature -6 degrees C, dew point -9 degrees C, and an altimeter setting of 29.96 inches of mercury. Additional relevant meteorological information indicated that the entire region was dominated by a high pressure region, resulting in visual meteorological conditions (VMC) with no or high ceilings, and generally easterly winds of 10 knots or less. The density altitude was calculated to be between 8,500 and 9,300 feet.
Wreckage and Impact Information
The accident site was in a partially forested area, with coordinates of 43.726 degrees N, 110.217 degrees W, at an elevation of approximately 9,550 feet above mean sea level. The ground in the immediate vicinity was relatively flat but sloped, with uneven terrain in the general locale, and the region was mountainous wilderness. The entire area was snow-covered, with deep snow on the ground near the wreckage.
The helicopter came to rest on its right side in a stand of evergreen trees approximately 80-100 feet high. One of those trees bore a diagonal cut, separating its top about 50 feet above the ground. The tree had a diameter of approximately 1 foot at that location. The fuselage was essentially intact, with minimal intrusions into the occupiable volume. All cabin doors remained attached and operable but damaged. Of the ten cabin transparencies, only the aft left door transparency was intact. All four main rotor blades were fracture-separated from the rotor mast/hub. The tail boom was fracture-separated into several sections. The empennage, including the aft vertical fin, tail rotor gearbox, and tail rotor, was fracture-separated from the tail boom. The two tail rotor blades remained attached to the tail rotor hub, which remained attached to the gearbox. The engine remained intact and attached to the airframe. There was no fire.
Wreckage examination revealed no evidence of pre-impact deficiencies or failures that would have prevented normal operation and continued flight. The engine mounted structure was intact and properly secured. No oil or fuel leaks were observed. N1 and N2 rotor systems rotated smoothly, and gear train continuity was confirmed. No impact damage or foreign object ingestion was evident. The Engine Control Unit (ECU) was visually undamaged, and data extraction showed the engine responded normally to control inputs. The Directional Control Actuator (DCA) passed functional checks with no anomalies.
Additional Information
GPS data from two handheld devices showed the helicopter departed Jackson about 1225, arrived in the search area about 1241, and conducted various search maneuvers. The last segment of the flight occurred between 1300:24 and 1301:53, with groundspeed decreasing from about 25 knots to less than 15 knots while at an altitude of about 9,680 feet MSL. The helicopter impacted trees and ground about 1301:53.
A small tree near a trail sign showed a damaged top, but examination indicated the damage was not consistent with being struck by the helicopter or tail rotor. The helicopter's weight at the time of the accident was estimated between 3,965 and 4,100 lbs, and it was within its hover performance envelope.