Hobe Sound, FL, USA
N80WH
Beech F33
During low-altitude cruise flight, the engine lost total power and the pilot performed a forced landing on an embankment next to a road, resulting in substantial damage to the right wing, right tip tank, and right elevator. Postaccident examination of the engine revealed that the crankshaft was fractured between the No. 2 main bearing journal and the No. 2 connecting rod journal and exhibited evidence of lubrication distress. Additionally, the No. 2 bearing had shifted, and a large portion of the bearing had extruded from the bearing support. The bearing support mating surfaces displayed fretting and the lock tab had completely worn away. Based on the observed damage, it is likely that the No. 2 main bearing shifted, resulting in inadequate lubrication to, and subsequent failure of, the crankshaft. While the crankcase mating surfaces displayed unapproved sealant material with no signs of silk thread, which was not consistent with the engine manufacturer’s guidance for engine assembly, the breakaway through bolt torque remained at or above the manufacturer’s specification. It could not be definitively determined, based on available evidence, if the use of an unapproved sealant contributed to the bearing shift.
On August 23, 2019, about 0946 eastern daylight time, a Beech, F33A, N80WH, was substantially damaged when it was involved in an accident near Hobe Sound, Florida. The private pilot and two passengers were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that his preflight inspection of the airplane revealed no anomalies and that he departed on the flight to look at properties. While in cruise flight, he heard a “tap, tap, tap, tap and a bang” and recalled the engine oil pressure gauge reading 0. The airplane was below 1,000 ft mean sea level (msl), and he began looking for a forced landing site. The pilot flew under powerlines, performed a forced landing on the embankment next to the roadway, and the airplane continued to slide until it came to rest. The airplane sustained substantial damage to the right wing, right tip tank, and right elevator. According to the airframe maintenance logbook, the airplane’s most recent annual inspection was completed on April 21, 2018, at a total time of 4,591.2 hours. The most recent 100-hour inspection was completed on May 17, 2019, at an aircraft total time of 4,670.6 hours. At that time, the oil and oil filter were replaced. The logbook entry included that the filter was cut open and “no defects were noted.” The aircraft total time at the time of the accident was 4,674.7 hours. According to the engine logbook, the engine had accrued 1,139.1 hours since it was overhauled on August 1, 2004. Examination of the engine revealed that the engine crankcase displayed a crack near the aft section of the spine. All 12 through bolt torque values were above the manufacturer's recommended torque values of 490 to 510 in-lbs torque. The outer crankcase mating surfaces displayed evidence of an unapproved sealant material with no signs of silk thread. The area around the Nos. 1 and 2 bearing support through bolt holes displayed a significant amount of fretting between the mating surfaces, while the Nos. 3 and 4 bearing support mating surfaces also displayed some fretting. The No. 1 bearing support displayed minor lock tab elongation, while the No. lock tab had completely worn away. The Nos. 1 and 2 bearings displayed signatures consistent with bearing shift, with the No. 2 bearing displaying the most movement. A large portion of the No. 2 bearing had extruded from the bearing support. The crankshaft was fractured between the No. 2 main bearing journal and the No. 2 connecting rod journal. Both sides of the crankshaft fracture surface exhibited thermal discoloration and incipient signatures of lubrication distress. The maintenance and overhaul manual for the IO-550-B engine described the proper assembly procedures. This section provided part numbers for approved sealant and grade silk thread to be used during assembly. The manual also warned against using unapproved sealants, stating: WARNING Do not apply any form of sealant to the crankcase cylinder deck, chamfer, cylinder mounting flange, cylinder base O-ring, cylinder fastener threads or crankcase main bearing bosses. The use of RTV, silicone, Gasket Maker or any other sealant on the areas listed above during engine assembly will cause a loss of cylinder deck stud or through-bolt torque. Subsequent loss of cylinder attachment load, loss of main bearing crush and/or fretting of the crankcase parting surfaces will occur. The result will be cylinder separation, main bearing movement, oil starvation and catastrophic engine failure. USE ONLY CLEAN 50 WEIGHT AVIATION ENGINE OIL ON SURFACES LISTED.
A bearing shift, which resulted in a loss of lubrication to the crankshaft, the failure of the crankshaft, and a total loss of engine power.
Source: NTSB Aviation Accident Database
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