Thermal, CA, USA
N15KH
Harwood Kenneth Lancair 360A
The airplane collided with power lines during a forced landing following a loss of engine power. The pilot reported that while maneuvering at 2,000 feet the engine began losing power. The pilot decided to divert to a nearby airport to make the emergency landing. While en route to the alternate airport, the pilot observed a part of the engine departing through the cowling and the engine lost complete power. At that point he knew he was not going to make it to the airport and decided to make a forced landing on a highway. Examination of the engine showed that the number three cylinder separated from the crankcase at the mounting pad due to the separation of its mechanical attachments. Once the cylinder separated, the piston then became unsupported, which resulted in the subsequent separation of the connecting rod from the crankshaft journal. Severe fretting signatures were found on the cylinder flange and crankcase mounting pad. The threads on the top hold down studs were undamaged and indicated that these nuts became loose and backed off. The studs on the bottom of the cylinder were fractured in overload and separated at a level consistent with the upper surface of the cylinder mounting flange.
HISTORY OF FLIGHT On February 6, 2006, about 1025 Pacific standard time, an experimental Lancair 360A, N15KH, lost engine power and collided with power lines during a forced landing near Thermal, California. The pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The private pilot and the certified flight instructor (CFI) were not injured; the airplane sustained substantial damage. The purpose of the local instructional flight was to conduct a biennial flight review. The flight departed Palm Springs, California, about 1000. Visual meteorological conditions prevailed, and no flight plan had been filed. The approximate global positioning system (GPS) coordinates of the primary wreckage were 33 degrees 34 minutes north latitude and 116 degrees 09 minutes west longitude. A National Transportation Safety Board investigator interviewed the pilot. The pilot stated that he was maneuvering at 2,000 feet over the Salton Sea when the airplane lost engine power. The pilot decided to divert to Thermal. Shortly thereafter, a part of the engine came out of the cowling. He was unable to make it to Thermal airport and attempted to land on Highway 66. During the approach, the airplane collided with power lines and then impacted onto Highway 66. On April 25, 2006, an examination of the engine by the National Transportation Safety Board investigator revealed there was a separation of the number three cylinder assembly from its respective mounting pad on the crankcase. The piston of the cylinder was observed lying on top of the cylinder barrel near the base. There was no evidence of fire observed. The number three cylinder and piston with the attached connecting rod were removed for further examination. There was no evidence of foreign object ingestion or detonation within the combustion chamber. The intake and exhaust valves remained intact and situated in their respective valve seats. The piston remained intact with the connecting rod attached. The piston sustained semicircular impressions on the dome and damage around the circumference of the skirt. The piston and corresponding cylinder barrel surface exhibited no evidence of heat distress consistent with lubrication deprivation. The piston rings were absent from their respective ring lands. The connecting rod end at the crankshaft separated from the journal. The crankshaft journal and connecting rod exhibited no heat distress consistent with lubrication deprivation. The connecting rod cap exhibited severe mechanical deformation and remained attached to the rod by one of the two rod bolts. The other rod bolt and respective rod bearing were not recovered. The crankshaft remained intact and exhibited no heat distress. The journal bearing surface appeared normal with the exception of subsequent impact damage from the detached connecting rod. Visual examination of the surrounding internal components of the engine revealed no evidence of mechanical malfunction or heat distress. The cylinder mounting flange and corresponding deck of the crankcase exhibited significant fretting signatures around the circumference of the mounting contact surface. Five of the eight cylinder hold down bolt studs were broken off, and the three remaining studs were predominantly undamaged at the threads. Specifically, the bottom four cylinder hold down studs were each broken off about the same length, which corresponded to the thickness of the cylinder flange. Each of the four studs cross sections exhibited signatures consistent with overload. The detached sections of the subject studs were not recovered. The cylinder hold down studs at the top of the remained intact with the exception of one, which was broken off. The threads of the subject studs remained predominantly undamaged. None of the corresponding nuts were recovered. According to FAA Advisory Circular AC 20-27F, Certification and Operation of Amateur-Built Aircraft, "Amateur builders are free to develop their own designs or build from existing designs. We do not approve these designs and it would be impractical to develop design standards for the wide variety of design configurations, created by designers, kit manufacturers, and amateur builders."
A loss of engine power caused by the separation of the number three cylinder due to the improper torque on the hold down nuts.
Source: NTSB Aviation Accident Database
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