# NTSB SEA00LA173: Cessna T210N, N6993N, Council, ID, August 28, 2000 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: August 28, 2000, 10:50 local (16:50 UTC) - Place: Council, ID - Coordinates: 44.889076, -116.539482 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=44.8891&lon=-116.5395&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 3 minor, 3 uninjured - Status: Completed, report July 2, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 50115 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA00LA173 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/50115/pdf - Page: https://openairdocs.org/ntsb/SEA00LA173 ## Probable cause the fatigue failure of the crankshaft due to improper overhaul procedures. Factors include a soft area in the field where the forced landing took place. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power, cruise - engine assembly,crankshaft - fractured (cause) - engine assembly,crankshaft - fatigue (cause) - maintenance,overhaul,major - improper, company maintenance personnel (cause) - Forced landing, descent - emergency - Nose over, landing - roll - terrain condition - soft (contributing factor) ## Analysis While in cruise flight, the turbocharged aircraft's manifold pressure began to drop. Although the engine continued to run smoothly, the pilot elected to divert to an alternate airport in order to check things out. When the aircraft was about four miles from the alternate airport, the engine began to run rough, and ultimately ceased producing power. Although the pilot was able to touch down in an open field short of the airport, during the landing roll, the nose wheel encountered an area that had been softened by irrigation, and the aircraft nosed over. During the investigation it was determined that the crankshaft failed due to fatigue crack initiation in the number two main journal cheek. Further inspection revealed that a sealant had been applied to the mating faces of the main bearing saddles the last time the engine was overhauled. Application of this sealant, which is not called for in the engine overhaul manual, lead to a loss of proper crankcase clamping pressure in the area of the main bearing saddle through-bolts. Loss of this pressure resulted in bearing shift and scoring of the crankshaft journal. ## Factual narrative On August 28, 2000, approximately 1050 mountain daylight time, a Cessna T210N, N6993N, nosed over during a forced landing after experiencing a total loss of engine power near Council, Idaho. The commercial pilot and two of his five passengers received minor injuries, and the aircraft, which was owned and operated by SP Aircraft, of Boise, Idaho, sustained substantial damage. The three other passengers were not injured. The aircraft, which was on a 14 CFR Part 135 air taxi flight from Slate Creek Airstrip to Boise, was being operated in visual meteorological conditions. The flight was on company flight following while en route. The ELT, which was activated by the accident sequence, was turned off at the scene. According to the pilot, while in cruise flight, the manifold pressure of the turbocharged aircraft began to slowly drop from about 27 inches of mercury to less than 24 inches of mercury. Because the engine appeared to continue to run smooth, the pilot thought that the engine turbocharger had ceased to function. Because he was nearing Council, the pilot decided he would land there and "check things out." When he was about four miles from the airport, the engine started to run very rough. It continued running rough for about 30 seconds, and then experienced a total loss of power. Being unable to get the engine to restart, the pilot made a forced landing in an open field to the northeast of Council. Although the touchdown was successful, during the landing roll, the nose wheel sank into an area that had been softened by irrigation, and the aircraft nosed over. In a post-accident engine teardown inspection it was determined that the crankshaft had failed in the cheek area between the number two main journal and the number two crank pin. It was also determined that the mating surfaces of the main bearing saddles showed signs of fretting. The most severely fretted was the number two main bearing saddle, through which a through-bolt passes. The number one main bearing was deformed, scored and discolored. The number two main bearing was deformed and fragmented. The crankcase and crankshaft were subjected to a visual and metallurgical inspection at the National Transportation Safety Board's Materials Laboratory. That inspection determined that what appeared to be silk thread and some form of sealant had been applied to the mating faces of the main bearing saddles during the last crankcase reassembly. Further inspection determined that the crankshaft failed due to fatigue, which initiated from the surface at the aft cheek radius of the number two center main crankshaft journal. Shifting of the number two main bearing had produced scoring in the cheek radius, leading to fatigue crack initiation. A review of the Teledyne Continental Motors 520 series engine overhaul manual current at the time this engine was overhauled (March, 1999) revealed that although aviation grade D silk thread and aviation Permatex are called for in mating the perimeter of the crankcase, instruction 70-20-00 (Crankcase Threading Procedure) and figure 70-20 (Permatex and Threading Procedure) specifically forbid application of any sealing material on the main bearing saddle mating faces. In a telephone conversation with Continental Motors analytical staff, the NTSB investigator-in-charge (IIC) was informed that application of any material on the mating surface of the main bearing saddles can lead to a loss of proper crankcase clamping force in the area of the through-bolts. If this force is lost, proper bearing crush forces are not maintained, and bearing shift may occur. As a result of bearing shift, the crankshaft my ultimately fail due to scoring and/or improper lubrication. ## Aircraft - Registration: [N6993N](https://openairdocs.org/aircraft/N6993N), registered now, S/N 21063202, built 1979 (OpenAirDocs) - Reported make and model: Cessna T210N - Registry model: [Cessna T210N](https://openairdocs.org/model/cessna-t210n) (registry code 2073456) (OpenAirDocs) - Registry engine: [Continental TSIO-520 series](https://openairdocs.org/engine/continental-tsio-520-series) (registry code 17040, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 21063202 - Airframe hours: 2420 - Engines: Continental TSIO-520-R 310 horsepower reciprocating - Damage: Substantial damage - Flight: Part 135 - Registered owner: Scott M. Patrick - Airworthiness certificate: Standard, Normal; Standard, Utility - Last inspection: Annual, August 1, 2000, 91 hours before - Departed: 1S7, SLATE CREEK, ID - Destination: BOI, BOISE, ID - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 70; commercial; airplane ratings: single-engine land, single-engine sea, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 7,800 total, 1,500 in this make and model, 6,800 as pilot in command, 200 in the last 90 days, 80 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Visibility: 20 statute miles - Lowest ceiling: none - Temperature: 55 °F ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20000828012859A](https://openairdocs.org/incident/20000828012859A), Aug 28, 2000: Cessna T210N, Council, ID, No damage. (-23) The pilot furnished the following info: during cruise flight, the engine started running erratically and continued to worsen until the engine quit. An… ## Other investigations on N6993N (2) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB WPR13CA271](https://openairdocs.org/ntsb/WPR13CA271), Jun 14, 2013: Cessna T210N (N6993N), Salmon, ID, substantial damage. Probable cause: The pilot's decision to land on a wet grass airstrip, which resulted in a main landing gear collapse after a collision with rough terrain. - [NTSB FTW85FA257](https://openairdocs.org/ntsb/FTW85FA257), Jun 15, 1985: Cessna T210N (N6993N), Mineral Wells, TX, destroyed From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.