# NTSB ANC17LA022: Piper PA 18-150, N82563, Chugiak, AK, April 30, 2017 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: April 29, 2017, 16:00 local (Apr 30, 2017, 00:00 UTC) - Place: Chugiak, AK - Coordinates: 61.41611, -149.50666 - Nearby events: https://openairdocs.org/map.md?lat=61.4161&lon=-149.5067&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Alaska Regional Office - Parties: Federal Aviation Administration (FAA) - NTSB case key (mKey): 95103 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC17LA022 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/95103/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=95103 - Page: https://openairdocs.org/ntsb/ANC17LA022 ## Probable cause A fracture and collapse of the main landing gear. Contributing to the accident was corrosion to the hydrasorb lug fitting. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: main gear strut/axle/truck](https://openairdocs.org/ntsb-findings/01023213): Aircraft › Aircraft systems · Fatigue/wear/corrosion (probable cause); cases with it: [Piper PA-18-150, 2 cases](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=7101828), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01023213/cases.md) - [Maintenance: scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Piper PA-18-150, 1 case](https://openairdocs.org/ntsb-findings/02062010/cases.md?model=7101828), [All aircraft, 320 cases](https://openairdocs.org/ntsb-findings/02062010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) (defining event); cases with it: [Piper PA-18-150, 16 cases](https://openairdocs.org/ntsb-events/094/sequence.md?model=7101828), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) ## Analysis The pilot was landing the airplane on a gravel runway when the right main landing gear collapsed; subsequently, both wings struck the ground. A postaccident examination revealed that the outer radius of the attaching lug on the extension tube that connected the wheel axle to the left main landing gear shock unit was fractured at the shock unit attachment. Visual examination of the fractured lug fitting revealed a flat fracture surface that was perpendicular to the long axis of the fitting, which had extensive evidence of rust and pitting throughout the circumference of the fitting. ## Factual narrative On April 29, 2017, about 1600 Alaska daylight time, a Piper PA-18 airplane, N82563, sustained substantial damage when it was involved in an accident in Chugiak, Alaska. The pilot and one passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that upon touchdown on a gravel runway, the right main landing gear collapsed. Subsequently, both wings struck the ground, resulting in substantial damage. The main landing gear were equipped with hydrasorb shock units, which consisted of automotive-type oleo struts combined with light shock cords. The hydrasorb’s outboard end was typically connected to the wheel axle by an extension tube, which was attached to the shock unit by a lug fitting and a through bolt. A postaccident examination of the right main landing gear system revealed that the hydrasorb shock unit’s extension tube lug fitting was fractured through the radius where it would typically be bolted to the hydrasorb’s outboard end. Examination of the broken lug fitting revealed a flat fracture perpendicular to the long axis of the fitting. The fracture surface had evidence of extensive rust and pitting throughout the circumference of the fitting. ## Aircraft - Registration: [N82563](https://openairdocs.org/aircraft/N82563), registered now, S/N 18-7709014, built 1977 (OpenAirDocs) - Reported make and model: PIPER PA 18-150 - Registry model: [Piper PA-18-150](https://openairdocs.org/model/piper-pa-18-150) (registry code 7101828) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 18-7709014 - Year built: 1977 - Airframe hours: 1900 - Engines: LYCOMING 0-320 A2A 150 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, May 19, 2016, 59 hours before - Departed: Ninilchik, AK - Destination: PABV, Chugiak, AK - Airport: PABV, Birchwood, runway 20L, 2,200 × 50 ft, gravel ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 54; injuries: none; private; airplane ratings: single-engine land; medical: class 3, waiver time limited special; last flight review August 23, 2016; seat: front; flight hours: 827.5 total, 235.6 in this make and model, 827.5 as pilot in command, 17.6 in the last 90 days, 9.3 in the last 30 days, 3.7 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 260° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 52 °F - Altimeter: 30.10 inHg - Observed at: PABV ## Other investigations on N82563 (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 DEN81FTG13](https://openairdocs.org/ntsb/DEN81FTG13), Jul 23, 1981: Piper PA-18 (N82563), Palermo, ND, substantial damage ## Docket (4 files) The files NTSB released with the investigation on January 8, 2021, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=95103. 5.5 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 4.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11635885&FileExtension=pdf&FileName=ANC17LA022%20NTSB%206120_Redacted-Rel.pdf - PA-18-150 super cub ipc (main landing gear diagram, including hydrasorb) (item 2, PDF, 1 page, 74 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11635665&FileExtension=pdf&FileName=PA-18_150_SuperCub%20IPC-Rel.pdf - Exemplar hydrasorb assemby showing lug fittings (item 3, PDF, 1 page, 27 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11635471&FileExtension=pdf&FileName=hydrasorb-Rel.pdf - Photo array (item 4, PDF, 3 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11635709&FileExtension=pdf&FileName=ANC17LA022%20Photo%20Array-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.