# NTSB ERA18LA168: Stinson L 5, N45TX, Thomson, GA, June 14, 2018 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: June 14, 2018, 18:00 local (22:00 UTC) - Place: Thomson, GA - Coordinates: 33.62611, -82.496109 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.6261&lon=-82.4961&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: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Eastern Region Aviation - Parties: FAA FSDO - NTSB case key (mKey): 97483 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA18LA168 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/97483/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=97483 - Page: https://openairdocs.org/ntsb/ERA18LA168 ## Probable cause Failure of maintenance personnel to inspect the crankshaft after two previous propeller strikes, which resulted in failure of the crankshaft and a total loss of engine power. Contributing to the crankshaft failure was insufficient torque applied to the thrust nut. ## 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 · Damaged/degraded (probable cause); cases with it: [Stinson L-5, 1 case](https://openairdocs.org/ntsb-findings/01058520/cases.md?model=8630202), [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 · Inadequate inspection (probable cause); cases with it: [Stinson L-5, 1 case](https://openairdocs.org/ntsb-findings/01058520/cases.md?model=8630202), [All aircraft, 233 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md) - [Maintenance: scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Stinson L-5, 1 case](https://openairdocs.org/ntsb-findings/02062010/cases.md?model=8630202), [All aircraft, 320 cases](https://openairdocs.org/ntsb-findings/02062010/cases.md) - [Inspection: scheduled/routine inspection](https://openairdocs.org/ntsb-findings/02061520): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Stinson L-5, 1 case](https://openairdocs.org/ntsb-findings/02061520/cases.md?model=8630202), [All aircraft, 167 cases](https://openairdocs.org/ntsb-findings/02061520/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: [Stinson L-5, 1 case](https://openairdocs.org/ntsb-events/340/sequence.md?model=8630202), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Maneuvering: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341); cases with it: [Stinson L-5, 2 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=8630202), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Landing-flare/touchdown: Ditching](https://openairdocs.org/ntsb-events/441); cases with it: [Stinson L-5, 1 case](https://openairdocs.org/ntsb-events/441/sequence.md?model=8630202), [All aircraft, 186 cases](https://openairdocs.org/ntsb-events/441/sequence.md) ## Analysis While in cruise flight, the pilot noticed an increase in oil temperature and loss of oil pressure. Shortly thereafter, the engine lost total power, and the propeller stopped rotating. The pilot performed a forced landing to a lake, which resulted in substantial damage. Examination revealed that the propeller could not be rotated by hand, and the crankshaft was fractured at the No. 2 crank pin. Review of maintenance logbooks revealed that the most recent engine overhaul was performed about 24 years and 711 flight hours before the accident. Since that time, the propeller had been removed and replaced on two separate occasions due to propeller strikes. There was no record of any crankshaft inspections following either of the propeller strikes, contrary to manufacturer guidance. Additional damage found on the Nos. 1 and 2 cylinders was caused by the crankshaft failure and pistons that impacted their respective rods and skirts. In addition to the main fracture, a separate crack was discovered slightly aft of the No. 1 main bearing and had propagated nearly the width of the crankshaft, but had not fully failed. The thrust nut, which required 375 ft-lbs of torque, was easily removed without effort or special tools, indicating that it was torqued to a value significantly below specification. This could cause axial play along the crankshaft and contribute to the progression of the crankshaft failure that was likely initiated during the previous 2 propeller strikes. The crankshaft likely failed after its structural integrity was compromised during previous propeller strikes. The improper torque on the thrust nut likely exacerbated the failure of the crankshaft. ## Factual narrative On June 14, 2018, about 1800 eastern daylight time, a Stinson L-5, N45TX, was involved in an accident near Thomson, Georgia. The commercial pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that the preflight inspection, engine runup, takeoff, and climb were normal. About 40 minutes into the flight, while flying at 2,200 ft mean sea level and 10 miles from the departure airport, he noticed the oil temperature “jumped” to the top of the green arc and the oil pressure was near the bottom of the green arc. He reduced engine power, adjusted the mixture to full rich, and turned toward the airport. Shortly thereafter, the engine lost total power and the pilot’s attempts to restore power were unsuccessful; the propeller was stationary and did not move during attempts to restart the engine. The pilot performed a forced landing to a lake and the airplane sank after the pilot egressed. The airplane was recovered and visually examined by a Federal Aviation Administration (FAA) inspector. The airplane’s left wing was substantially damaged. The inspector attempted to rotate the propeller by hand, but the propeller would not move. Review of the maintenance logbooks revealed that the last engine overhaul was performed on March 29, 1994. On two separate occasions, June 8, 2002, and September 16, 2002, the propeller was replaced due to a propeller strike/damage. There was no record of crankshaft inspections found in the maintenance logbooks. The last annual was performed on September 14, 2017, at 6,113.2 tachometer time. At the time of the accident, the airplane had flown 10.6 hours since the annual inspection and 711 hours since engine overhaul. The airplane was recovered for detailed teardown and examination of the engine. Removal of the Nos. 1 and 2 cylinders revealed that the crankshaft fractured at the No. 2 crank pin. (see Figure 1.) Figure 1 Crankshaft fracture The thrust nut was removed in order to open the crankcase. The amount of torque required to loosen the thrust nut was not measured, but was significantly less than the 375 ft-lbs specified by the engine overhaul manual, as it required no special tools and little effort to remove. Upon opening the crankcase, it was confirmed that the crankshaft was fractured along with ancillary damage caused by the Nos. 1 and 2 pistons and connecting rods impacting their respective skirts. In addition to the main fracture, a separate crack was discovered slightly aft of the No. 1 main bearing that had propagated nearly the width of the crankshaft, but had not fully failed. On October 18, 2016, Lycoming issued a Mandatory Service Bulletin No. 533C (Superseded 533B) with recommended action for sudden engine stoppage, propeller/rotor strike, or loss of propeller/rotor blade or tip for all Lycoming reciprocating aircraft engines. The SB included detailed checklists for the inspection. ## Aircraft - Registration: [N45TX](https://openairdocs.org/aircraft/N45TX), registered now, S/N 44-17397 (OpenAirDocs) - Reported make and model: STINSON L 5 (C) - Registry model: [Stinson L-5](https://openairdocs.org/model/stinson-l-5) (registry code 8630202) (OpenAirDocs) - Category: Airplane - Serial number: 44-17397 - Year built: 1944 - Airframe hours: 1641 - Engines: Lycoming O-435 185 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, September 14, 2017, 10 hours before - Departed: HQU, Thomson, GA - Equipment: Electronic flight bag or handheld device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 47; injuries: none; flight instructor, commercial, private; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, waiver time limited special; seat: front; restraint: 4-point; flight hours: 528 total, 92 in this make and model, 469 as pilot in command, 1 in the last 90 days, 0 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 290° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 72 °F - Altimeter: 30.00 inHg - Observed at: HQU, 6 nm away ## 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 20180614007889A](https://openairdocs.org/incident/20180614007889A), Jun 14, 2018: Stinson L-5, Thomson, GA, Substantial damage. On June 14, 2018 at approximately 1740 local time, a Stinson aircraft, model L-5 make a force landing into lake strom thurman in Thomson Georgia. The cause of… ## Docket (5 files) The files NTSB released with the investigation on November 3, 2021, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=97483. 9.5 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12454307&FileExtension=pdf&FileName=N45TX_Lux_6120_1_Redacted-Rel.pdf - FAA inspectors examination reports (item 2, PDF, 5 pages, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12455976&FileExtension=pdf&FileName=FAA%20Inspectors%20Examination%20Reports_Redacted-Rel.pdf - Maintenance logbook excerpt (item 3, PDF, 1 page, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12459350&FileExtension=pdf&FileName=Maintenance%20Logbook%20Excerpt_Redacted-Rel.pdf - Service bulletin prop strike inspections (item 4, PDF, 23 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12462785&FileExtension=pdf&FileName=Service%20Bulletin%20Prop%20Strike%20Inspection_Redacted-Rel.pdf - Photo array_ airplane and engine damage (item 5, PDF, 3 pages, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12459464&FileExtension=pdf&FileName=Photo%20Array_Airplane%20and%20Engine%20Damage-Rel.pdf 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.