# NTSB WPR10LA004: Cessna 172A, N7810T, Payson, AZ, October 3, 2009 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: October 3, 2009, 09:00 local (16:00 UTC) - Place: Payson, AZ - Coordinates: 34.256668, -111.339164 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.2567&lon=-111.3392&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-flare/touchdown: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report December 20, 2010 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 74844 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR10LA004 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74844/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74844 - Page: https://openairdocs.org/ntsb/WPR10LA004 ## Probable cause The stress corrosion cracking of the nose gear landing fork, which resulted in the fork's failure during landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: nose/tail gear attach section](https://openairdocs.org/ntsb-findings/01023221): Aircraft › Aircraft systems · Fatigue/wear/corrosion (probable cause); cases with it: [Cessna 172A, 1 case](https://openairdocs.org/ntsb-findings/01023221/cases.md?model=2072404), [All aircraft, 29 cases](https://openairdocs.org/ntsb-findings/01023221/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-flare/touchdown: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Cessna 172A, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=2072404), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Landing: Loss of control on ground](https://openairdocs.org/ntsb-events/230); cases with it: [Cessna 172A, 2 cases](https://openairdocs.org/ntsb-events/230/sequence.md?model=2072404), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) ## Analysis The pilot reported that, as the airplane touched down, the nose gear separated and the airplane veered to the left before coming to rest on the runway. During the event the right wing was substantially damaged. Postaccident examination of the separated nose landing gear fork indicated that the alloy used for forging the part was 2014 series aluminum, which is susceptible to stress corrosion cracking (SCC) given the proper environment and a continuous stress state. A Safety Board metallurgist concluded that the fracture characteristics were consistent with SCC, with slow crack growth over time. The crack appeared to have originated from a point on the surface of the bolt hole bore and propagated upwards and outwards. The last annual inspection of the airplane was conducted about two weeks prior to the accident, although the investigation was unable to determine if the crack would have been visible to the unaided eye during a routine inspection. ## Factual narrative On October 3, 2009, at 0900 mountain standard time, a Cessna 172A, N7810T, was landing at Payson Airport, Payson, Arizona, when the nose landing gear fork separated during landing and the pilot lost control of the airplane. The student pilot was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. The student pilot, who was also the registered owner of the airplane, was not injured. The airplane was substantially damaged. Visual meteorological conditions prevailed and no flight plan was filed. The flight departed from Payson Airport about 0800. According to the student pilot, he was conducting his second or third landing. As the airplane touched down, the nose gear separated, the airplane veered to the left, and then impacted the runway. The right wing sustained substantial damage. The student pilot indicated that the previous owner of the airplane had landed on unimproved terrain quite frequently. The nose landing gear fork was submitted to the National Transportation Safety Board Materials Laboratory for further examination. According to the metallurgist, the part was manufactured using 2014 series aluminum, and the fracture surface had two distinct regions. One portion of the fracture was a relatively flat area with evidence of corrosion, and the remainder of the fracture consisted of slanted irregular surfaces with a shiny crystalline appearance. The metallurgist indicated that the appearance of corrosion was consistent with slow crack growth over time. Scanning electron microscope examination of the corrosion crack revealed no fracture features consistent with fatigue. Further examination revealed that the propagation of the crack appeared to be intergranular with cracks branching into adjacent grains. Although no single origin was positively identified, the metallurgist indicated that the crack appeared to have originated from a point on the surface of the bolt hole bore and propagated upwards and outwards. It was not possible to determine if the crack would have been visible to the unaided eye during a routine inspection. ## Aircraft - Registration: [N7810T](https://openairdocs.org/deregistered/N7810T-2011-01-19), registration cancelled 2011-01-19, S/N 47410, built 1960 (OpenAirDocs) - Reported make and model: CESSNA 172A - Registry model: [Cessna 172A](https://openairdocs.org/model/cessna-172a) (registry code 2072404) (OpenAirDocs) - Registry engine: [Continental 0-300 series](https://openairdocs.org/engine/continental-0-300-series) (registry code 17022, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 47410 - Airframe hours: 4369 - Engines: Teledye Continental Motors O-300 145 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, September 23, 2009, 1 hours before - Departed: PAN, Payson, AZ - Destination: PAN, Payson, AZ - Flight plan: Unknown - Airport: PAN, Payson Airport, runway 24, 5,500 × 75 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 56; injuries: none; medical: class 3, with waivers/limitations; seat: left; flight hours: 70 total, 70 in this make and model, 40 in the last 90 days, 30 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 130° at 6 knots, gusting 15 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 66 °F, dew point 28 °F - Altimeter: 29.95 inHg - Observed at: SEZ, 42 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 20091003019539A](https://openairdocs.org/incident/20091003019539A), Oct 3, 2009: Cessna 172A, Payson, AZ, Substantial damage. On October 3, 2009 student pilot terry reynolds was soloing his aircraft, a Cessna 172, registered N7810T. He went on a local flight to the practice area,… ## Docket (5 files) The files NTSB released with the investigation on August 16, 2010, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74844. 2.8 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 795 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40331545&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Photo 1. Accident Site (Provided by PD) (item 2, .PDF, 451 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40331550&FileExtension=.PDF&FileName=Photo%201.%20Accident%20Site%20(Provided%20by%20PD)-Master.PDF - Photo 2. Nose Gear (Provided by PD) (item 3, .PDF, 736 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40331552&FileExtension=.PDF&FileName=Photo%202.%20Nose%20Gear%20(Provided%20by%20PD)-Master.PDF - Photo 3. Nose Gear View Two (Provided by PD) (item 4, .PDF, 608 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40331553&FileExtension=.PDF&FileName=Photo%203.%20Nose%20Gear%20View%20Two%20(Provided%20by%20PD)-Master.PDF - Materials Laboratory Factual Report 10-070 (item 5, .PDF, 250 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40332866&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report%2010-070-Master.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.