Fredericksburg, PA, USA
N40337
MAULE M-4-220C
The pilot reported that, while the airplane was in cruise flight, the engine began to vibrate and lose power. The pilot shut down the engine and performed a forced landing to a field. During the landing roll, the airplane nosed over and was substantially damaged. Examination of the engine revealed that the No. 4 cylinder head was partially separated and that the No. 4 piston pin was fractured. The piston pin fractured due to fatigue that had initiated at the pin's outer diameter, and the fracture corresponded to the location of the pin bearing separation from the connecting rod. The bearing fracture surface was obliterated. It is likely that pin and bearing wear altered the stress distribution and precipitated the failure. A review of maintenance records revealed that the 41-year-old engine had been operated for about 1,400 total hours since new and about 50 flight hours since its most recent annual inspection, which was performed about 1 year before the accident. In addition, the No. 4 cylinder was overhauled about 23 years and 560 flight hours before the accident. It was also removed, reconditioned, and reinstalled about 4 years and 165 flight hours before the accident.
On June 1, 2013, about 0830 eastern daylight time, a Maule M-4-220C, N40337, operated by a private individual, was substantially damaged during a forced landing, after it experienced a total loss of engine power shortly after takeoff from Farmers Pride Airport (9N7), Fredericksburg, Pennsylvania. The airline transport pilot sustained minor injuries and a passenger was not injured. Visual meteorological conditions prevailed and no flight plan had been filed for the flight destined for Baublitz Commercial Airport (9W8), Brogue, Pennsylvania. The personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91.The pilot reported that he departed 9N7 and had climbed to an altitude of 2,500 feet mean sea level, when the engine began to vibrate and lose power. In addition, the cabin began to fill with white smoke. The pilot shut-down the engine and performed a forced landing to a soy bean field. During the landing roll, the airplane entered a wheat field and nosed over, which resulted in substantial damage to the fuselage and vertical stabilizer. The airplane was manufactured in 1972 and equipped with a Franklin 6A-350-C1, 220-horsepower engine. Initial examination of the engine by a Federal Aviation Administration inspector revealed that the No. 4 cylinder head was partially separated from the cylinder barrel, the No. 4 cylinder piston was fragmented, and the No. 4 piston pin was fractured. The No.4 cylinder, connecting rod, fractured piston pin, and piston fragment were forwarded to the NTSB Materials Laboratory, Washington, DC, for further examination. Examination of the retained engine components by an NTSB metallurgist revealed that the No. 4 piston pin was circumferentially fractured near its midpoint. The connecting rod was not fractured, but the piston pin bearing in the small end was fractured and damaged. The separation surface of the bearing was completely obliterated. When installed, the piston pin fracture corresponded to the separation location of the piston pin bearing in the connecting rod. Additional examination of the piston pin fracture features with a scanning electron microscope revealed striations consistent with fatigue propagation that initiated at the pin outer diameter. The No. 4 piston fragment which was estimated to comprise about one-third of the piston crown was severely battered. Almost all of the fracture surfaces were obliterated by mechanical damage; however, the few undamaged fracture areas appeared typical of overstress separations. The No. 4 cylinder was fractured through its bore consistent with overstress features on both the aluminum cylinder and steel liner, with no indications of preexisting cracking. According to maintenance records, the airplane and engine had been operated for about 50 hours since its most recent annual inspection, which was performed on June 27, 2012. The engine had been operated for about 1,400 total hours since new. In addition, the No. 4 cylinder was overhauled during June 1990, about 560 hours prior to the accident, and was also removed, reconditioned, and reinstalled during April 2009, about 165 hours prior to the accident.
A total loss of engine power due to the fatigue failure of the No. 4 cylinder piston pin.
Source: NTSB Aviation Accident Database
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