Kahului, HI, USA
N58267
Hughes 369D
The helicopter was damaged during a hard landing following a loss of tail rotor control. The pilot was conducting a tour flight when tail rotor control was lost. He conducted an emergency landing and landed hard when the helicopter encountered a gust of wind. Examination of the tail rotor system revealed that the tail rotor control rod failed about 6.5 inches forward of its aft attach point, where the control rod attaches to the tail rotor pitch change bell crank. The control rod fractured perpendicular to its longitudinal axis and displayed a flat fracture surface. Metallurgical examination of the control rod fracture revealed that it failed as a result of fatigue cracking that propagated from the outside in. The crack origin could not be determined due to severe mechanical damage from relative movement between the fracture mating surfaces. Due to the damage, the size of the crack could not be determined, and therefore, an assessment of the crack's age could not be made. As a result, it was not possible to determine whether or not the crack would have been visible during the last inspection, which took place 91.2 hours prior to the accident. That inspection's checklist called for the removal and inspection of the tail rotor control rod.
HISTORY OF FLIGHT On October 14, 2005, at 1113 Hawaiian standard time, a Hughes 369D helicopter, N58267, sustained minor damage when it made a hard landing at the Kahului Airport, Kahului, Hawaii, following the failure of its tail rotor control rod while in cruise flight. The commercial helicopter pilot and his 4 passengers were not injured. The helicopter was operated by AlexAir (d.b.a. Alika Aviation) as a sightseeing tour flight under the provisions of 14 CFR Part 135. Visual meteorological conditions prevailed and a company visual flight rules flight plan was filed. The local tour flight originated from Kahului approximately 1000. According to the pilot's written statement, tail rotor control was lost during the tour flight. He confirmed the loss of tail rotor control and declared an emergency with the control tower in Kahului. He then briefed his passengers on the emergency landing. The pilot attempted to maintain airspeed and turn into the wind, but the helicopter continued to slip with no turn. The pilot set up for a sliding landing onto the heliport tarmac area and encountered a gust of wind about 5 to 10 feet above the ground. The helicopter fishtailed and began a 360-degree rotation. The pilot rolled the throttle to idle and the helicopter contacted the ground and spun around before coming to a stop in an upright position. The helicopter sustained damage to the landing skids, struts, and mountings. AIRCRAFT INFORMATION Review of the helicopter maintenance records revealed the helicopter accumulated 24,575.2 total hours at the time of the event. It underwent its last 100-hour inspection on September 13, 2005, at a helicopter total time of 24,478.9 hours. Its last 300-hour inspection took place on September 15, 2005, at a total time of 24,484.0 hours. Review of the helicopter's 300-hour inspection checklist revealed that under the section titled "Drive Train" mechanics were to "remove the tailboom control rod and inspect for wear through hard anodized surface (Ref. Tailboom Control Rod Replacement); inspect grommets for wear and deterioration." This inspection instruction referenced chapter 67-20-10, which states under the section titled "Anti-Torque Flight Controls (Two and Four Blade) Inspection/Check" that the person conducting the inspection should check the control rod "...for surface damage and evidence of bending..." and "...inspect tailboom control rod surfaces that pass through all grommets. Serviceable wear is limited to thickness of hard anodic coating. Check that all bushings are secure." WRECKAGE AND IMPACT INFORMATION According to the operator and the FAA inspector who responded to the event, the tail rotor control rod failed about 6.5 inches forward of its aft attach point (where the control rod attaches to the tail rotor pitch change bell crank). The tail rotor control rod fractured perpendicular to its longitudinal axis and displayed a flat fracture surface. During post-event examination of the tail rotor control rod, it was noted that the grommet, which was normally positioned in the tailboom's most aft support area, was displaced aft of the grommet area about 4 inches and was resting on the tail rotor control rod. The tail rotor control rod displayed additional rub damage where it contacted the support metal in the absent grommet area. Closer examination of the rub damage revealed another longitudinal and lateral crack. Segments of the failed tail rotor control rod and the loose grommet were shipped to the NTSB Materials Laboratory in Washington, D.C. for further examination. TESTS AND RESEARCH Metallurgical examination of the control rod at the NTSB Materials Laboratory revealed that fracture surfaces contained severe mechanical damage from relative movement between the mating fractures. The fracture faces at the inside and outside diameter edges showed evidence of metal flow that also resulted from mechanical contact between the mating fractures. The external face of the tube was coated with paint and there was no evidence of mechanical damage, such as a gouge or tool mark on the external face of the tube. Scanning electron microscope examination of the fracture face revealed valleys within the damaged area. One of the valleys contained an isolated region that contained striations typical of a fatigue crack. The crack propagation was toward the inside diameter, but the origin of the fatigue crack could not be determined due to the extensive mechanical damage to the fracture face. The grommet also contained a fracture that extended around the circumference, but it showed no evidence of a pre-existing crack. Due to the damage to the crack faces from their relative movement against each other, a determination of crack length and width could not be determined.
The fatigue cracking and failure of the tail rotor control rod during cruise flight, which resulted in a hard landing during the precautionary landing.
Source: NTSB Aviation Accident Database
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