The NTSB has retained hydraulic fluid and system components for further examination into the fatal April 26 crash of an air ambulance–configured 2006 Airbus Helicopters AS350B2 operated by Air Methods. The helicopter went down in a wooded area in Northern Wisconsin near Hazelhurst at approximately 10:50 p.m. local time on a Part 91 repositioning flight that originated in Madison, Wisconsin at 9:04 p.m. The helicopter had accumulated 5,152.8 hours total airframe time and had undergone 100- and 600-hour inspections the day before the accident. It was equipped with EGPWS (enhanced ground proximity warning system) and an Appareo Vision 1000 recorder and SD card that were damaged in the crash but recovered for analysis.
According to the report, the helicopter took on 80 gallons of fuel before departing KMSN for the flight to its home heliport, 60WI, about 8.4 nm from the crash scene. Fuel was present at the crash scene but there was no fire. Three area airports closest to the crash scene reported calm winds, 10 miles visibility, clear skies, and narrow/no temperature/dewpoint spreads with the temperature right at/just above freezing. The NTSB noted that the impact path was steep through trees beginning with “a tree about 70 feet tall about 66 degrees and 47 feet from the nose of the wreckage [that] had their trunks and branches broken and linearly separated. A ground impression about 11 feet by 9 feet and 2 feet deep was found in front of the helicopter wreckage.” The cockpit and cabin were destroyed. All three rotor blades were attached to the hub and the hub rotated when the transmission input drive shaft was rotated by hand.
An examination of the hydraulic system revealed “a magnetic plug in the hydraulic system has some particulate on its magnetic end. The filter bypass button on the hydraulic control block was popped. The hydraulic pump was turned by a drill and the pump exhibited a suction and pressure at the pump's inlet and outlet. Disassembly of the hydraulic pump revealed scoring witness marks on the pump housing in its gear's plane of rotation and no debris or obstructions were observed within the pump ports,” the NTSB said.