Rock Springs, WY, USA
N46ME
PIPER PA46-500TP
During the takeoff roll, as the airplane approached 70 knots, it started slowly pulling to the right. The pilot immediately aborted the takeoff and stopped the airplane on the runway using brakes and reverse propeller thrust. The pilot inspected the airplane and found that the right main landing gear tire had blown, and the right aileron had buckled at the aileron midspan hinge location. There were no scuff marks or indentations to indicate that the hinge or area around the hinge had been struck by debris. The hinge was still attached to the aileron, but the attach bracket that connected the hinge to the wing had fractured. Metallurgical examination revealed that the failure of the hinge bracket was the result of overstress forces applied to the hinge. Overstress failure of only the midspan hinge is somewhat unusual when none of the other hinges were damaged, which suggests modal vibration forces concentrated at this particular hinge. It is likely that the flat tire could have induced the vibratory mode in the aileron at the midspan hinge.
HISTORY OF FLIGHT On May 3, 2011, at 1740 mountain daylight time, the pilot of a Piper PA46-500TP, N46ME, aborted the takeoff at Rock Springs-Sweetwater County Airport, Rock Springs, Wyoming, after the right main landing gear tire failed. The airline transport pilot operated the airplane under the provisions of Title 14 Code of Federal Regulations, Part 91. The pilot was not injured, and the right aileron was substantially damaged. Visual meteorological conditions prevailed, and an IFR flight plan had been filed. The pilot reported that during the takeoff roll, as the airplane approached 70 knots, it started slowly pulling to the right. He immediately aborted the takeoff, and stopped the airplane on the runway using brakes and reverse propeller thrust. The pilot inspected the airplane and found the right main landing gear tire blown, and the right aileron buckled at the aileron center hinge location. There were no scuff marks or indentations to indicate that the hinge or area around the hinge had been struck by debris. The hinge was still attached to the aileron, but the attach bracket that connected the hinge to the wing had fractured. The operator removed the entire hinge component and associated pieces. The hinge pieces were sent to the NTSB Materials Laboratory for examination. TESTS AND RESEARCH The NTSB Materials Laboratory examination revealed that the aileron hinge attach brackets were each fractured at three places. The fractures were all located at manufactured bend locations. Optical examinations of the fracture faces revealed deformation and fracture features consistent with overstress separations. Further observation with a scanning electron microscope uncovered ductile dimples on the fracture surfaces indicating both shearing and tensile overstress forces. No indications of progressive separation or corrosion were found. Photographs of the blown tire, Goodyear Flight Special II, part number 606C81B1, serial number 8029718, were examined by a technical representative of Goodyear Aviation Tires. The technical representative’s assessment of the blown tire was that it appeared to be a typical “run-flat” condition. The distorted shape, blue rubber, and the liner appearance was consistent with that of a tire that had been run overdeflected (underinflated and/or overloaded) during use in service. The upper sidewall appears to have been cut from the adjacent areas of the tire by running between the wheel flange and runway surface due to the overdeflected condition. ADDITIONAL INFORMATION The airplane manufacturer reported that they had knowledge of a similar incident that occurred on January 20, 2010, on a different PA46. In this instance, a main tire blew, and the aileron center hinge failed in a similar fashion. Piper Aircraft’s engineering department is currently investigating the hinge and the unusual phenomena associated with the hinge failure.
The overstress fracture of the right aileron midspan hinge bracket due to modal vibrations created by a deflated right main landing gear tire during the takeoff roll.
Source: NTSB Aviation Accident Database
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