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Preliminary Safety Board Findings on Fatal EMS Helicopter Crash

Air Safety Week, Jan 21, 2008

Operating Emergency Medical Services (EMS) rotorcraft remains a dangerous enterprise.

According to the National Transportation Safety Board (NTSB), on Sunday Dec. 30, 2007, at 0306 Central Standard Time, a Bell 206L-3 (N109AE) owned and operated by Air Evac EMS crashed while maneuvering near Cherokee, Alabama.

The Air Evac Lifeteam, including a pilot, paramedic, and flight nurse were fatally injured. Night visual meteorological conditions prevailed, and no flight plan was filed for the local search for a lost hunter.

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According to Air Evac EMS, the flight was initiated after they were notified of a missing hunter, who may have been injured or suffering from exposure. The flight was a voluntary mission, as the operator would not receive payment for the flight unless the hunter required air transport to a hospital.

The flight departed Northwestern Alabama Regional Airport (MSL), Muscle Shoals, AL about 0200, and arrived over the search area about 0215.

Personnel were on the ground searching for the hunter and witnessed the accident. They reported that the helicopter crewmembers were about to terminate the search, when ground personnel heard a gunshot, which they perceived as a signal from the lost hunter. The ground personnel followed the gun shot noise, and located the hunter's vehicle.

The helicopter illuminated a searchlight and located the hunter. The helicopter crewmembers intended to maintain the light on the hunter until ground personnel located him.

"At that time, the helicopter was about 100 to 150 feet above the trees, and in a hover or very slow flight, when the witnesses heard a decrease in engine noise, followed by an increase in engine nose. They then observed the helicopter spinning right, with a 'fireball' near the engine exhaust, as it descended vertically into wooded terrain. The helicopter subsequently came to rest inverted, and a post crash fire ensued," the NTSB preliminary report stated.

The wreckage was examined at the site on December 30 and 31. The accident site was located in the Freedom Hills Wildlife Management Area, a large hunting preserve with trees ranging in height about 60 to 80 feet. Numerous tree strikes were noted in the immediate vicinity above the main wreckage, and the terrain near the wreckage sloped 20 to 30 degrees.

The main wreckage consisted of the cockpit, fuselage, and a majority of the tail boom. The wreckage was oriented about a 345-degree magnetic heading, at an elevation approximately 725 feet above mean sea level (msl). The cockpit and fuselage were consumed by fire. The tail boom had separated about 1 foot aft of the tail boom attach point. That separation exhibited crushing damage, consistent with ground impact overstress separation.

The aft section of tail boom separated about two feet aft of the horizontal stabilizer. The aft tail boom separation point exhibited cutting damage from left to right, which was consistent with main rotor blade strike damage. The aft portion of the tail boom, upper portions of the left vertical fin, and tail rotor assembly were found approximately 150 feet southeast of the main wreckage. The forward end of the tail cone also exhibited left to right damage consistent with a main rotor blade strike.

Numerous pieces of tail boom shards and a damaged section of tail rotor drive shaft were found in an arc from east to south, about the same distance from the main wreckage as the aft tail cone and tail rotor assembly. Among the shards was a partial piece of tail rotor drive shaft, and two pieces of the upper left vertical fin, which had been cut from left to right, consistent with main rotor blade contact.

Both main rotor blades were found in the wreckage, and had separated about three feet outboard of the rotor hub. They were partially burned and exhibited leading edge damage and red paint transfer, consistent with one or more tail boom strikes. The outboard sections of the rotor blades exhibited s- bending, consistent with tree and ground impact.

Continuity of the main rotor drive train was confirmed from the engine, through the K-Flex shaft, to the transmission, and through the main rotor mast. The mast was imbedded in the ground and extended through the main rotor hub. The trunion remained attached to the top of the mast by the mast retention nut. The inboard section of the main rotor blades remained attached to the hub at ground level. The main rotor pitch change links were separated mid-span consistent with overstress. Continuity of the tail rotor drive train, and the tail rotor pitch change linkage was established from the engine, to the tail rotor, except for the damaged locations where the tail boom separated.

The Rolls-Royce powerplant sustained post crash fire damage and is undergoing further examination.

The helicopter was inspected four days prior to the accident. The helicopter had flown 4.9 hours since that inspection, and had accumulated 5,087 total hours of operation at the time of the accident.

Government Industry

Preliminary Safety Board Findings on Fatal EMS Helicopter Crash

Air Safety Week, Jan 21, 2008

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