# NTSB DEN08LA163: Beech C23, N6714E, Duncan, OK, September 28, 2008 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: September 28, 2008, 15:25 local (20:25 UTC) - Place: Duncan, OK - Coordinates: 34.470832, -97.959724 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.4708&lon=-97.9597&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: Minor injuries - Injuries: 2 minor - Status: Completed, report June 11, 2009 - Report: Approved by Office Director - Parties: Federal Aviation Administration - NTSB case key (mKey): 69223 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN08LA163 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/69223/pdf - Page: https://openairdocs.org/ntsb/DEN08LA163 ## Probable cause A total loss of engine power due to the fatigue failure of the engine crankshaft. Contributing to the accident were the improper maintenance to the engine crankshaft, improper reassembly of the engine, and failure to follow the engine manufacturer's overhaul manual. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (reciprocating): recip engine power section](https://openairdocs.org/ntsb-findings/01058520): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Beech C23, 1 case](https://openairdocs.org/ntsb-findings/01058520/cases.md?model=1151242), [All aircraft, 233 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md) - [Engine (reciprocating): recip engine power section](https://openairdocs.org/ntsb-findings/01058520): Aircraft › Aircraft power plant · Fatigue/wear/corrosion (probable cause); cases with it: [Beech C23, 1 case](https://openairdocs.org/ntsb-findings/01058520/cases.md?model=1151242), [All aircraft, 233 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md) - [Maintenance: repair](https://openairdocs.org/ntsb-findings/02062015): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Beech C23, 1 case](https://openairdocs.org/ntsb-findings/02062015/cases.md?model=1151242), [All aircraft, 99 cases](https://openairdocs.org/ntsb-findings/02062015/cases.md) - [Engine (reciprocating): recip engine power section](https://openairdocs.org/ntsb-findings/01058520): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Beech C23, 1 case](https://openairdocs.org/ntsb-findings/01058520/cases.md?model=1151242), [All aircraft, 233 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md) - [Use of equip/info: use of manual](https://openairdocs.org/ntsb-findings/02063020): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Beech C23, 2 cases](https://openairdocs.org/ntsb-findings/02063020/cases.md?model=1151242), [All aircraft, 15 cases](https://openairdocs.org/ntsb-findings/02063020/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Beech C23, 1 case](https://openairdocs.org/ntsb-events/340/sequence.md?model=1151242), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Emergency descent: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341); cases with it: [Beech C23, 10 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=1151242), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) ## Analysis During the local flight, the airplane's engine began to violently shake and the pilot elected to shut down the engine and perform an emergency landing to a field. The airplane impacted a fence and terrain, which resulted in a bent firewall and left wing. A review of the maintenance records showed that, approximately 23 hours prior, the engine had experienced a loss of engine oil due to faulty maintenance during an annual inspection. The engine underwent maintenance and the airplane was returned to service. Examination and disassembly of the engine revealed that the crankshaft had fractured into 3 sections and that improper maintenance had been performed on several engine components. Metallurgical examination of the crankshaft revealed that the crankshaft had been improperly reworked which resulted in fatigue and crankshaft failure. The crankshaft rework and engine reassembly did not follow the manufacturer's overhaul manual. ## Factual narrative On September 28, 2008, at 1525 central daylight time, a Beech C23 single-engine airplane, N6714E, sustained substantial damage when it impacted terrain following a loss of engine power while maneuvering near Duncan, Oklahoma. The private pilot, who was the registered owner, and passenger sustained minor injuries. Visual meteorological conditions prevailed for the Title 14 Code of Federal Regulations Part 91 personal flight. The local flight departed Duncan approximately 1500. The pilot, who purchased the airplane in February 2008, flew the airplane from Guthrie, Oklahoma, to Duncan on a 1.3 hour flight with no problems noted. The passenger boarded the airplane in Duncan, and the pilot performed a run-up prior to the local flight. At an altitude of 2,500 mean sea level (msl), the engine RPM dropped, and the engine "shook violently." The pilot attempted to troubleshoot the engine problem; however, the engine vibration continued. The pilot elected to shut down the engine and execute a forced landing to a field. During the forced landing, the airplane impacted a fence and terrain. Examination of the airplane revealed the firewall and left wing were bent and buckled. The tachometer showed 1,688 hours at the time of the accident. A review of the Lycoming O-360-A4K (s/n: L26749-36A) engine maintenance records revealed the engine underwent its most recent "annual" inspection on December 20, 2007, at a tachometer time of 1,661.8 hours. During the inspection, the engine oil cooler lines were replaced and no additional anomalies were noted. On January 21, 2008, at a tachometer time of 1,664.8 hours, the engine underwent maintenance due to an engine oil leak caused by a crack oil cooler elbow fitting. Included in that maintenance was the disassembly of the engine and replacement of the rod bearings, main crankshaft bearings, and piston rings. The engine was test run and leak checked with no anomalies noted. The engine maintenance records stated that the maintenance was done in accordance with the Lycoming Overhaul Manual. On October 21, 2008, the engine was examined and disassembled at the facilities of Air Salvage of Dallas, Lancaster, Texas, under the supervision of a NTSB investigator, and three Federal Aviation Administration (FAA) inspectors. According to a FAA inspector's report, examination of the engine revealed the wrong gasket was installed on the oil filter adapter assembly, the oil filter contained metal debris, the piston rings were worn and did not exhibit etched part numbers, and the oil rings were different between the 4 pistons. Internal examination of the engine revealed the crankshaft was fractured into 3 sections, 2 of the 8 tappets exhibited pitting, the aft main bearings and rod bearing part numbers matched the January 2008 engine maintenance record entry, however, the front main bearings did not match the part number indicated in the record. The fractured crankshaft was retained for metallurgical examination. The fractured crankshaftwas examined by the NTSB materials laboratory. Examination of the crankshaft revealed the crankshaft was fractured in two places; one fracture occurred forward of the number 2 crankshaft journal and one fracture occurred aft of the number 3 crankshaft journal. The features on both fracture surfaces were consistent with fatigue crack propagation with crack initiation at the journal radii. Circumferential crack arrest lines were observed on both fracture surfaces and ratchet marks were visible on the forward fracture surface, consistent with fatigue crack growth. The crack arrest lines and ratchet marks pointed towards the journal radius as the initiation site for both fatigue cracks. Size measurements of the crankshaft journals were consistent with material removal from some of the journals. Three of the four crankshaft journals were undersized. Journal numbers 2 and 4 were undersized by 0.003 inch, and number 3 was undersized by 0.005 inch. According to the Lycoming Overhaul Manual, the crankshaft journal diameters may be reduced by 0.003 inch by polishing without renitriding the crankshaft. In that event, it is advised that all journals be polished to the same size. Grinding is not advised as it may penetrate the nitride layer at the journal radius leaving the crankshaft prone to fatigue failure. If a journal is polished to undersize, the code "M03P" should be stamped as a suffix to the part number on the flange. There was no code suffix found on the flange. If a journal is reduced by more than 0.003 inch, the journals should be ground to undersize, the shaft renitrided and the code "RN" stamped as a suffix to the serial number on the flange. There was no code suffix found on the flange. In addition, there was no documentation noted in the maintenance records that the shaft had been renitrided. ## Aircraft - Registration: [N6714E](https://openairdocs.org/deregistered/N6714E-2011-01-07), registration cancelled 2011-01-07, S/N M-2200, built 1979 (OpenAirDocs) - Reported make and model: BEECH C23 - Registry model: [Beech C23](https://openairdocs.org/model/beech-c23) (registry code 1151242) (OpenAirDocs) - Registry engine: [Lycoming O&VO-360 series](https://openairdocs.org/engine/lycoming-o-vo-360-series) (registry code 41514, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: M-2200 - Airframe hours: 1688 - Engines: Lycoming O-360-A4K 180 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Donald G. Holloway - Registered owner: Donald G. Holloway - Airworthiness certificate: Standard, Normal - Last inspection: Annual, December 20, 2007, 26 hours before - Departed: DUC, Duncan, OK - Destination: DUC, Duncan, OK ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 53; injuries: none; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review June 4, 2007; seat: left; flight hours: 113 total, 27 in this make and model, 52 as pilot in command, 11 in the last 90 days, 3 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 100° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 81 °F - Altimeter: 30.12 inHg - Observed at: DUC ## 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 20080928848009A](https://openairdocs.org/incident/20080928848009A), Sep 28, 2008: Beech C23, Duncan, OK, Substantial damage. (-23) Pilot was at cruise altitude of 2500' and reported a loss of power. The engine started running rough and exhibited a severe vibration. Pilot shut the… ## Other investigations on N6714E (1) 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 ANC82DA030](https://openairdocs.org/ntsb/ANC82DA030), Apr 4, 1982: Beech C23 (N6714E), Kenai, AK, substantial damage 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.