ATL99LA131
ATL99LA131

On September 11, 1999, at 1730 central daylight time, a Hiller UH-12A helicopter, N212W, collided with the ground while on approach to land in Satartia, Mississippi. The helicopter was operated by the commercial pilot under the provisions of Title 14 CFR Part 91, and visual flight rules. Visual meteorological conditions prevailed and no flight plan was filed for the local flight. The commercial pilot and one passenger received minor injuries, and the helicopter sustained substantial damage. The flight originated from a private airstrip in Satartia, Mississippi, at 1715.

According to the pilot, he departed the airstrip and flew north approximately two to three miles, and decided to land in an open area next to a soybean field due to a physical urgency. He stated that during the approach to the selected landing site, he flew on a westerly heading, then initiated a left turn toward the east. After completing 90 degrees of the turn, a "loud noise occurred" and the helicopter became "uncontrollable," with the control stick moving forcefully in all directions. At the time, the airspeed was approximately 30 mph with an altitude of 25 to 30 feet above ground level (agl). The helicopter began to turn to the left and the flight controls failed to respond to the pilot's control inputs. The helicopter impacted the ground in a slight right bank. Upon impact, the helicopter rolled onto its right side, sustaining damage to the main rotor blades, the tail boom, the skids, and the fuselage.

During the examination of the accident site, all helicopter parts and components were confined to a 300-foot radius of the main wreckage. The metal leading edge from one main rotor blade was located approximately 300 feet northwest of the accident site. The tail rotor blades had no leading edge damage. The forward section of the tail rotor drive shaft was located 250 feet southwest of the accident site. Six engine cooling fan blades were found beginning at a starting point approximately 250 feet northwest of the accident site, scattered along a 100-foot distance to the southeast. The forward upper engine/transmission mounts were found separated from the airframe and were subsequently sent off to the NTSB Materials Laboratory in Washington, D.C., for further examination.

An examination of the helicopter's maintenance records revealed that the helicopter was purchased as a military surplus aircraft on August 27, 1971, and was issued an FAA standard airworthiness certificate on that date. The last annual inspection was performed on December 1, 1998, and the helicopter had accrued 146.9 hours since the last inspection. According to the logbooks, the upper engine mounts had not been changed in accordance with the FAA Airworthiness Directive AD-56-27-02 which was issued in 1956 to address the repair of defective welds in the clamp lug area of engine mounts in all UH-12, UH12A, and UH-12B helicopters. All engine mounts that were not cadmium plated and were stamped with a "7" or "8" or no stamp at all were required to be removed and rewelded.

Metallurgical inspection of the two engine mounts revealed no evidence of cadmium in the clamp lug region as determined by energy dispersive x-ray spectroscopy. Also, no stamps were observed. No entries in the maintenance records indicating compliance with AD 56-27-02 were found. The fracture surfaces on the engine mounts were irregularly shaped, consistent with overstress separation failure.

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