PHOENIX, AZ, USA
N100PL
Kaman HH-43F
Ground witnesses reported seeing the helicopter disintegrate in-flight, about 250 feet above ground level. The helicopter impacted the ground in a nearly inverted attitude, scattering rotor blade fragments on both sides of a canal. The ex-military, medium lift helicopter with twin intermeshing rotors was en route to perform an off-airport lift operation. It operated in the 'restricted' category and was required to fly over unpopulated areas. At the time of the accident, it was flying parallel with a canal. Examination of the wreckage revealed that the fixed horizontal stabilizer left outboard leading edge attach fitting had fractured and exhibited evidence of a pre-existing crack. A second attach fitting aft of the leading edge attachment was also fractured. Additionally, the operator had installed automotive dampers in lead-lag positions on the rotor blades.
HISTORY OF FLIGHT On September 25, 1999, about 0642 hours mountain standard time, a Kaman HH-43F helicopter, N100PL, was destroyed when it collided with terrain at Phoenix, Arizona. The commercial rated pilot and crewman were both fatally injured. Moseley Aviation, Inc, d.b.a. Pro-Lift Helicopters, Litchfield Park, Arizona, was operating the positioning flight under the provisions of 14 CFR Part 91. Visual meteorological conditions prevailed and a company flight plan was filed. The flight originated about 0620 from an off-airport location at the west end of Phoenix. The operator obtained prior approval from the Federal Aviation Administration (FAA) to lift 58 air conditioning units onto two co-located buildings under 14 CFR Part 133, using the "Restricted" category helicopter. They also obtained approval to operate within a congested area. The route of flight was to be over washes and the canal. The operation was to be monitored by FAA inspector's on-scene. The pilot contacted the Phoenix-Deer Valley Municipal Airport control tower (ATCT) en route for permission to transition through their airspace west-to-east on the north side. The request was approved. About 20 minutes later, the tower was advised of the accident about 4 miles northwest of the airport. The helicopter was observed on the ATCT D-Brite radar level about 1,700 feet mean sea level (msl), and had traveled about 10 miles in 7 minutes. The accident site elevation is 1,450 feet msl. According to witnesses in the accident area, the helicopter exploded, or disintegrated in-flight over the Central Arizona Project (CAP) canal. PERSONNEL INFORMATION At the pilot's last second-class flight physical dated January 28, 1999, he reported a total of 775 flight hours with 65 hours in the last 6 months. According to FAA records, the pilot obtained his private pilots certificate on May 23, 1991. At that time he was rated for airplane single engine land. His application documented 56.5 total flight hours. On November 16, 1995, he was issued a private pilot rotorcraft-helicopter add-on rating. He reported 132 hours of fixed wing and 58.1 hours of rotorcraft flight hours. On January 6, 1996, the pilot was issued a commercial pilot rotorcraft-helicopter rating. He reported 133 hours of fixed wing time and 71.5 hours of rotorcraft time. According to excerpts from the pilot's flight log, at the time of the accident the pilot had accumulated about 1,739 total flight hours, with 298 fixed wing and 1,383 rotary wing. AIRCRAFT INFORMATION Two aircraft logbooks were examined. The most recent annual inspection occurred on June 24, 1999, at 5,139.0 hours. According to airframe logbook information, the last ATC transponder 24-month check per FAR 91.413 was accomplished on August 9, 1995. The helicopter was certificated in the "restricted" category for external load operations under 14 CFR Part 133. The helicopter design was altered/modified August 13, 1994. The original Lycoming T53-L11D, 1,100-shaft horsepower engine was replaced with a Lycoming T53-L-13B, 1,400-shaft horsepower engine. According to the documents, there was no change to the transmission-input horsepower. According to records, the helicopter was substantially damaged April 9, 1992, during a firefighting water bucket operation. The total time reported was 4,222.1 hours. The helicopter was substantially damaged again on December 11, 1992, during a collision with terrain at Columbia, South Carolina. The total time reported was 4,241.5 hours. The report stated that the fuel shutoff valve was found in the off position, and the solenoid valve sealant was soft and wet with jet fuel. According to the FAA type certificate holder, there had been problems with the type of sealant that holds the solenoid barrel into the valve body. With seal leakage of jet fuel into the solenoid area, the sealant becomes soft and allows the barrel to slip out of the valve body shutting off the fuel to the engine. The certificate holder alerted operators about the problem and recommended safety wiring the two sections together to prevent separation. During this accident examination, the fuel shutoff was separated and the sealant was soft and contaminated with jet fuel, but, it also had light impact damage to the valve. The assembly was not safety wired together. METEOROLOGICAL INFORMATION At 0657, the Phoenix-Deer Valley Airport ATCT was reporting: sky clear; visibility 30 miles; wind 320 degrees at 9 knots, and the altimeter was 29.96 inHg. WRECKAGE AND IMPACT INFORMATION The wreckage was viewed near the Central Arizona Project canal. The fuselage was found nearly inverted with total collapse of the cabin structure. A small post crash fire had occurred near the engine and had been contained by a local resident with a dry powder fire extinguisher. Both rotor shaft pylons and rotor hubs were found lying together with all four blade hubs and nearly symmetrical severing of the blades near the hubs. Helicopter rotor blade parts were found on both sides and in the canal. The main wreckage was found about 200 feet southeast of the canal. The tail stabilizer group was found about 150 feet west of the main wreckage. Examination of the vertical stabilizers and rudders revealed damage and inward bending of each vertical stabilizer rudder forward tip. According to the Kaman Aerospace investigators, it appeared to be caused by contact with the intermeshing rotor blades. The fixed horizontal stabilizer left outboard leading edge attach fitting was fractured and revealed a black sooty material around the fracture area. A second horizontal attachment bracket located aft of the leading edge attachment, and the stabilizer rivets in the bracket, were also fractured and exhibited black sooty discoloration around the fractures. The fracture surface of the bracket was abraded. Examination of the rotor system revealed Gabrial Pro-Rider Premium Gas Truck Shocks, P/N 737934, an automotive type shock absorber was installed along with the original blade dampers. Dampers are utilized to diminish or dampen the lead and lag action/oscillation of the main rotor blades. No documentation addressing the installation of the automotive type dampers was recovered. According to Kaman Aerospace, the automotive dampers were not compatible with the helicopter rotor system design. MEDICAL AND PATHOLOGICAL INFORMATION The Maricopa County Medical Examiner performed an autopsy on the pilot on September 27, 1999. During the course of the autopsy, samples were obtained for toxicological analysis at the FAA Civil Aeromedical Institute located in Oklahoma City, Oklahoma. The analyses were negative for carbon monoxide, cyanide, ethanol, and drugs. ADDITIONAL INFORMATION On March 15, 2001, the wreckage was released to the insurance company representative. Honeywell Product Safety and Integrity performed an engine teardown and examination. A copy of the report is attached. Chandler Evans Control Systems performed an examination of the TA-2S fuel regulator and PTG-4 power turbine governor. A copy of the report is attached. Additional parties to the post accident examination, Kaman Aerospace and Timber Choppers Transport Helicopters (the type certificate holder), failed to provide a written report to the Safety Board. The operator, Moseley Aviation, failed to return the Pilot/Operator Aircraft Accident Report.
Failure of the horizontal stabilizer left outboard forward attach point because of a previously existing crack that resulted from inadequate maintenance inspection by the operator. A factor was the use of automotive parts.
Source: NTSB Aviation Accident Database
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