Oakland, CA, USA
N6278C
CESSNA T210N
During a local photo flight at an altitude of 1,500 feet mean sea level (msl), the pilot reported a decrease in engine power followed by a complete loss of engine oil pressure. The pilot determined that due to his location and altitude, he was forced to make a landing on the water. During the landing, the airplane sustained substantial damage to the horizontal stabilizers and to the bottom of the fuselage. During the post-accident investigation, it was determined that the number two and three cylinders had been replaced 137.1 flight hours prior to the accident. During the engine examinations, thermal discoloration of the crankshaft main journals and damage to various other internal components were noted. The crankshaft was fractured just forward of the number two main bearing. The fracture surfaces of the crankshaft were mechanically damaged due to rotational forces. The number two main bearings were not found in the main bearing support diameters. Several bearing fragments were found in the oil sump and on the bearing support diameter. The crankcase itself had been compromised just above the number one cylinder. A review of the maintenance logbooks noted that the engine was beyond manufacturers' recommendations for time between overhaul. Several maintenance discrepancies and non-compliance with manufacturers' recommendations were also noted.
HISTORY OF FLIGHT On September 10, 2008, about 1350 Pacific daylight time (PDT), a Cessna T210N, N6278C, ditched in the San Francisco Bay following a loss of engine power, about 1/4 mile north of the Oakland Bay Bridge, Oakland, California. Ja-Mar Industries, Inc., DBA Air Flight Services, was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The commercial pilot and one passenger were not injured; the airplane sustained substantial damage to the tail and lower cowling area by impact forces. The local photo flight departed Reid-Hillview Airport of Santa Clara County (RHV), California, about 1320. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot reported that about 30 minutes after departing RHV, the engine started to lose power. He then noticed that there was no indicated oil pressure. He was flying about 1,500 feet mean sea level (msl) when the power loss occurred, and he decided the best place to land was on the water. Investigators examined the airplane after it was removed from the salt water. A hole was observed in the engine crankcase near the number two cylinder. The airplane was recovered for further investigation. AIRCRAFT INFORMATION The airplane was a Cessna T210N, serial number 21063853. A review of the airplane’s logbooks revealed that the airplane had a total airframe time of 8,147 hours at the last annual inspection. The logbooks contained an entry for an annual inspection dated June 1, 2008. The tachometer read 8010.7 at the last inspection; the tachometer read 8147.8 at the accident scene. The engine was a Teledyne Continental Motors TSIO-520-R, serial number 293904-R. The engine was installed on the airframe in September 1997. At the time of the accident, total time recorded since major overhaul was 2,866.8 hours. The manufacturer recommends 1,600 hours or 12 years between overhauls. The number two and three cylinders were replaced with serviceable items during the annual inspection on June 1, 2008. The total time since installation was 137.1 hours. TESTS AND RESEARCH Investigators examined the wreckage at Plain Parts, Sacramento, California, on September 17, 2008. Examination of the engine assembly revealed the following issues. The backbone area and associated hardware forward of the fuel manifold valve had a heavy coating of dark gray sealant. Fretting was found on the crankcase halves at the backbone area at the number five and six bolt attachments. The number three, five, and six cylinder bays were intact and undamaged. The number one, two, and four cylinder bays had mechanical damage. The number one cylinder bay had displaced material and a small hole from mechanical damage. All of the main bearing support mating surfaces exhibited rough surfaces and pitting from fretting. The number one main bearing support diameter had displaced material. The number two main bearing support lock-slot was elongated. The number two main bearing support diameter had displaced material and mechanical damage from bearing rotation and extrusion. The number two main bearings were not found in the main bearing support diameters. Several bearing fragments were found in the oil sump and on the bearing support diameter. The larger fragments had smearing of the surface babbit, exposing the copper layer. The number one and three main bearings had deformation, hard particle passage and smearing of the surface babbit, exposing the copper layer. The number four main bearing had gouges from hard particle passage, exposing the copper layer. The number five main bearing had normal wear. There were no signs of lubrication distress on any of the main bearings. The crankshaft separated into two sections between the number two connecting rod journal and the main bearing journal. The fracture surfaces of the crankshaft cheek had displaced material and thermal discoloration. ADDITIONAL INFORMATION A detailed review of the maintenance logbooks by the Federal Aviation Administration inspector participating in the investigation reported noting several discrepancies and non-compliance with manufacturers' recommendations throughout several inspections.
A loss of engine power while maneuvering due to the disintegration of the number two main bearing, which resulted in a fracture of the crankshaft. Contributing to the accident was inadequate maintenance.
Source: NTSB Aviation Accident Database
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