# NTSB DEN01LA089: Cessna 140A, N666TC, Greeley, CO, April 25, 2001 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: April 25, 2001, 10:00 local (16:00 UTC) - Place: Greeley, CO - Coordinates: 40.44057, -104.669219 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.4406&lon=-104.6692&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report February 20, 2002 - Report: Approved by Office Director - Parties: FAA Flight Standards District Office - NTSB case key (mKey): 52127 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN01LA089 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/52127/pdf - Page: https://openairdocs.org/ntsb/DEN01LA089 ## Probable cause total failure of the right main landing gear spring due to fatigue. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, landing - flare/touchdown - landing gear,main gear spring - failure,total (cause) - landing gear,main gear spring - fatigue (cause) ## Analysis The pilot made a conventional, full-stall landing. Upon touch down, the right main landing gear failed. The airplane skidded to a halt, buckling the fuselage and landing gear box, and damaging the wing spar. Metallurgical examiunation disclosed cracks had initiated in one of two holes used to attach the step assembly to the landing gear spring. Chevron (or beach) marks on the fractured surface pointed back to the crack initiation site, and were consistent with fatigue cracking. The adjacent area was characterized by dimples, indicating the final breakage was due to a ductile fracture under overload. ## Factual narrative On April 25, 2001, approximately 1000 mountain daylight time, a Cessna 140A, N666TC, was substantially damaged when the right main landing gear failed during landing at the Greeley-Weld County Airport, Greeley, Colorado. The recreational pilot, the sole occupant aboard, was not injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the personal flight being conducted under Title 14 CFR Part 91. The flight originated at Hudson, Colorado, approximately 0915. The following is based on a telephone interview with the pilot and the accident report he later submitted. The purpose of the flight was to practice pattern work accuracy and takeoffs and landings. The pilot made two low approaches to the runway at Greeley. On the third approach, he decided to make a landing. A full stall conventional landing was made. The right main landing gear broke on touch down and the airplane skidded to a halt. The fuselage and landing gear box were buckled, and the wing spar was damaged. Both fractured ends of the main landing gear were cut away and sent to the Cessna Aircraft Company's Material and Process (M&P) Engineering Department, where they were metallurgically examined. The following is based on Cessna's M&P report: The landing gear was made of 6150M steel, and microstructure examination disclosed it had a hardness and tensile strength that met Cessna's engineering specifications. Decarburization, approximately 0.015 inches in depth, was noted near the top surface of the landing gear. There was also deformation and roughening on the inside surface, consistent with shot-peening, also required by engineering specifications. Two holes, 3/16" in diameter, and two bolts and nuts were used to attach the step assembly to the landing gear spring. The bolts were not damaged. Florescent magnetic particle inspection revealed cracks had initiated at the top end of the lower hole. No cracking was observed at the inside end of the hole. The M&P report concluded that the landing gear spring cracked through the upper hole. Chevron (or beach) marks on the fractured surface pointed back to the crack initiation site, and were consistent with fatigue cracking. The fracture features were similar to quasi-cleavage, and faint crack arrest lines were observed. The fatigue region was very small, approximately 0.075 inches in depth. The adjacent area was characterized by dimples, indicating the final breakage was due to a ductile fracture under overload. ## Aircraft - Registration: [N666TC](https://openairdocs.org/deregistered/N666TC-2021-01-19), registration cancelled 2021-01-19, S/N 15399 (OpenAirDocs) - Reported make and model: Cessna 140A - Registry model: [Cessna 140A](https://openairdocs.org/model/cessna-140a) (registry code 2071604) (OpenAirDocs) - Registry engine: [Continental C90 series](https://openairdocs.org/engine/continental-c90-series) (registry code 17009, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 15399 - Airframe hours: 8243 - Engines: Continental C-90-12F 90 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: George Lair - Registered owner: Gregory W. Lair - Airworthiness certificate: Standard, Normal - Last inspection: Annual, June 15, 2000, 56 hours before - Departed: 18V, Hudson, CO - Destination: GXY, Greeley, CO - Airport: GXY, Greeley-Weld County, runway 09, 6,200 × 100 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 64; injuries: none; recreational; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; last flight review February 1, 2001; seat: left; flight hours: 131 total, 67 in this make and model, 30 as pilot in command, 21 in the last 90 days, 11 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 0° at 0 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 50 °F, dew point 43 °F - Altimeter: 30.31 inHg - Observed at: GXY ## 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 20010425008849A](https://openairdocs.org/incident/20010425008849A), Apr 25, 2001: Cessna 140A, Greeley, CO, No damage. (-23)Right main landing gear spring leg broke on landing. Upon examination of the gear leg, there is the appearance of a crack that had started at the bolt… 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.