DEN01FA058
DEN01FA058

HISTORY OF FLIGHT

On February 28, 2001, at 1024 mountain standard time, an air ambulance configured Bell 412 helicopter, N412SM, operated as Care Flight for Saint Mary's Hospital, Grand Junction, Colorado, by Petroleum Helicopters, Inc., was destroyed when it impacted the ground approximately 11 miles south of Grand Junction. The commercial pilot, the only person aboard, received fatal injuries. The flight was a local area post maintenance check flight flown under Title 14 CFR Part 91, and a company flight plan was filed. Visual meteorological conditions prevailed. The flight departed the hospital helicopter pad about 1000 and proceeded to the southeast.

The maintenance action involved replacement of both drive links, part number 412-010-405-109. With the change of these dynamic components, a check flight was required following the maintenance action. Vibration and autorotation characteristics were to be checked during the flight.

Witnesses described seeing the helicopter proceeding in a southerly direction at an altitude of 1,500 to 2,000 feet above the ground. One witness said the helicopter made some turns and headed back in a northerly direction. A witness, close to the accident site, said she saw the helicopter proceeding toward her and when it was within several hundred yards, it appeared to descend rapidly and slow down. Then, the rotor blades slowed and folded up over the helicopter. It then came down with little forward speed in a right hand turn, impacted the ground, and immediately began to burn. She said that when the rotors were slowing, she saw parts come off the helicopter and go through the rotor system. Other witnesses in the accident site area described seeing similar events with some describing one or more postimpact explosions.

One of the witnesses said she called 911 on her cell phone when it was obvious to her the helicopter was "in trouble." The fire department arrived approximately 10 minutes following the accident.

PERSONNEL INFORMATION

The pilot held a commercial pilot certificate with a rating in rotorcraft/helicopter and an instrument helicopter rating. He held a second class medical certificate, with no limitations, issued on February 10, 2000.

According to records provided by his employer, he received his initial flight training through the United States Army at Fort Rucker, Alabama. He was trained as a helicopter pilot with his initial training taking place between March 1, 1989, and January 1, 1990. He was rated as a helicopter pilot by the Army on January 9, 1990. His employment with Petroleum Helicopters started on February 6, 1997, and his previous employer was the Army National Guard.

As of January 31, 2001, he had accumulated 23 hours in single engine fixed wing aircraft and 3,703 hours in helicopters. His records provided information that as an employee of Petroleum Helicopters, he had 3 hours in the Bell 206, 1,859 hours in the Bell 212/412, 376 hours in the Bell 214, and 31 hours in the Aerospatiale 350. His military flying experience consisted of 300 hours in the UH-1H, 20 hours in the OH-58, and 1,090 hours in the AH-64. Of that time, 36 hours were spent conducting maintenance check (test) flights.

According to available information, the pilot had received no training from Petroleum Helicopters regarding the conduct of a maintenance check flight, nor does the Federal Aviation Administration (FAA) require such training.

As an employee of Petroleum Helicopters, the pilot had one physiological event where he passed out. Medical evaluation determined the episode was due to sleep deprivation and no repeat events took place. No other records of physiological events were found, and the pilot had no previous accident history recorded.

AIRCRAFT INFORMATION

According to Federal Aviation Administration (FAA) and Bell Helicopter records, the aircraft was manufactured in 1989 and the initial owner was Samsung Corporation of Korea. The helicopter was returned to the United States and placed in operation by Petroleum Helicopters in 1997, with a reported total airframe time of approximately 2,000 hours. According to Petroleum Helicopter records, the helicopter was configured for emergency medical operations with accommodations for 2 pilots, 4 passengers, and 3 litters. At the time of the accident, it had accumulated approximately 5,481 hours on the airframe.

The engines on the helicopter were PT6T-3B model/series engines manufactured by Pratt and Whitney of Canada. They were rated at 900 shaft horsepower each. The number 1 engine, serial number CPPS-62759, was manufactured in January 1984. It had accumulated 6,808 hours total time, 4 hours since overhaul, and was last inspected on February 10, 2001. The number 2 engine, serial number CPPS-TB0066, was manufactured in August 1998. It had accumulated 1,452 hours total time and had not been through overhaul. Like the number 1 engine, it was last inspected on February 10, 2001.

WRECKAGE AND IMPACT INFORMATION

The helicopter impacted on a southerly heading and came to rest in an upright position. Fire consumed the fuselage. The tail boom was fragmented from its forward attach point to approximately 18 inches forward of the horizontal stabilizers. The engines were detached from the airframe due to impact and fire, but remained in the area where they would have normally been mounted.

Based on witness information concerning pieces coming off the helicopter in flight, an extensive search was conducted back along the projected flight path of the helicopter. Several pieces of transmission cowling were found along this path. The pieces all came from around the top of the transmission cowling. They were fragmented, but did not exhibit heat or fire damage. In addition, pieces of main rotor blade cover material and blade core honeycomb material were found in the same area. Witness marks provided evidence that the main rotor control rod ends were at the level where impact damage was incurred on the cowl pieces.

The main gear box (transmission) remained intact but was damaged by both impact and fire. Rotation of the input quill produced normal rotation of the mast, and the main drive shaft outer coupling remained attached to the drive gear of the combining gearbox. The drive shaft forward inner coupling was intact as was the complete aft coupling assembly. Radial scoring was present on the exterior of the shaft.

The main rotor controls were still present on the mast but were damaged by both impact and fire. The controls were examined and no evidence of preimpact failure or malfunction was found.

The main rotor hub and blade assembly was damaged by impact and fire. The yokes were fractured in the inboard flexure area. The fractures were consistent with overload. The core portion of each fractured yoke remained attached to its respective spindle and damper bridge, and all were damaged by both fire and impact. No evidence of preimpact failure or malfunction was found.

All four main rotor blades were accounted for. Three of the blades were damaged by fire. All the blades were fractured between 51 and 84 inches from the inboard attach points in the area where the spar narrows. Triangular shaped skin sections were broken out of two of the blades adjacent to the fracture areas. The fracture areas exhibited upward bending indicative of overload failure and the leading edge of all blades contained damage consistent with object impact during rotation.

The hydraulic servo actuators were all damaged by impact and fire and exhibited numerous fracture areas consistent with impact overload. No evidence was found of pre impact failure or malfunction.

The tail boom was fragmented forward of the elevators and a crease was noted on the left side. The crease angled downward to aft of the elevators. The size and shape of the crease was consistent with the leading edge shape of the main rotor blades. The left stabilizer separated from the tail boom and was crushed aft from the leading edge toward the spar. The vertical stabilizer was fractured consistent with impact overload.

The tail rotor drive shaft was fractured in numerous places and the forward portion was damaged by fire. The hangar bearings and couplings were all accounted for and exhibited no functional defects. Both the 42 degree and 90 degree gear boxes were accounted for and exhibited impact damage. One tail rotor blade exhibited fire damage and the other exhibited impact damage with bending of about 45 degrees toward the tail boom. The control linkage was intact, but deformed from impact forces.

The engines exhibited both fire and impact damage, and the combining and accessory gear boxes were consumed by fire. There were no no indications found of any pre-impact failure or malfunction of any of the engine components examined. Both the left and right engine power turbines displayed light rotational signatures and static imprint marks characteristic of low rotational energy at the time of impact. Both the left and right gas generator section internal components displayed strong rotational signatures characteristic of the gas generator sections developing significant power at the time of impact. According to the manufacturer, this condition could result from high power selection and high power turbine back pressure due to low rotor speed.

TESTS AND RESEARCH

According to information provided by Bell Helicopter Textron, as the main rotor system slows while under aerodynamic load, the main gear box can "walk" (horizontal orbital movement) on its mounting structure. When this occurs, the control rod ends can come in contact with the transmission cowl.

ADDITIONAL DATA / INFORMATION

The wreckage was released to the insurance company representing the owner on March 6, 2001. No parts were retained.

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