# NTSB WPR18LA272: Smith AEROSTAR601, N90339, Heber, UT, September 25, 2018 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: September 25, 2018, 11:00 local (17:00 UTC) - Place: Heber, UT - Coordinates: 40.482776, -111.426109 - Nearby events: https://openairdocs.org/map.md?lat=40.4828&lon=-111.4261&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: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 98353 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR18LA272 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/98353/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=98353 - Page: https://openairdocs.org/ntsb/WPR18LA272 ## Probable cause A recent hard landing resulted in a fracture of a joint from a cylinder to a main landing gear. ## 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 · Failure (probable cause); cases with it: [Smith AEROSTAR 601P, 1 case](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=8360608), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01023213/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: [Smith AEROSTAR 601P, 2 cases](https://openairdocs.org/ntsb-events/094/sequence.md?model=8360608), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) ## Analysis The pilot stated he touched down normally and during the landing roll, the airplane veered left coming to rest off the runway surface. The airplane sustained substantial damage to the right wing and horizontal stabilizer. Postaccident examination of the landing gear assembly revealed that the weld had failed on the joint attached to the main landing gear cylinder and upper scissor assembly. Most of the fracture surface of the failure surface had been obliterated by smearing and grinding, consistent with post-fracture damage. The degree of the fracture surface damage was consistent with the fracture and separation happening before the accident. Landing gear components are under cyclic loads at every landing and during landing actions (such as braking or taxiing). There was no evidence of fatigue, corrosion, or other progressive mechanisms would have led to the fracture of this joint from the strut cylinder. It is likely that a recent hard landing fractured the joint from the cylinder, but it could not be determined whether this occurred during the accident landing or beforehand due to the damage incurred after the gear collapsed. ## Factual narrative On September 25, 2018 about 1100 mountain daylight time, a Smith Aerostar 601P, N90339, was substantially damaged when it was involved in an accident near Heber, Utah. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The personal cross-country flight departed from Brigham City Regional Airport (BMC), Brigham City, Utah, about 1030 with a planned destination of Heber. The pilot stated he touched down normally on runway 22 at Heber City Municipal Airport (HCR), Heber, Utah. During the landing roll, the airplane veered left and continued off the runway surface. Despite his attempts, the pilot was unable to regain control, and the right main landing gear collapsed. Upon egressing the airplane, the pilot observed that the left main landing gear had failed at the strut’s weld, and the airplane sustained substantial damage to… Postaccident examination of a portion of the left main landing gear assembly by the National Transportation Safety Board Materials Laboratory revealed that the weld had failed on the joint attached to the landing gear cylinder and upper scissor assembly. The inboard fitting of the joint remained affixed to the scissor assembly by an attachment bolt. The joint was loose where it attached to the cylinder, and it could be rotated against the cylinder exterior. The adjacent hexagonal cap below the loose joint was still tight against the cylinder assembly (see figure). Figure: Diagram and forward aft view picture of the left main landing gear The attachment joint had fractured and separated about the entire circumference of the cylinder exterior. This separation allowed the joint (and linkage) to rotate approximately 30° about the cylinder. The fracture surface of the attachment joint faced upward on the strut cylinder where the joint had been welded to the cylinder. Examination of the joint portions of the fracture surface, particularly along the fractured weld protrusions, did not reveal any fracture features. Portions of the external weld on the joint exhibited features of localized deformation, all of which were consistent with overstress fracture. Most of the fracture surface features had been obliterated by smearing and grinding, consistent with post fracture damage. The degree of the fracture surface damage was consistent with the fracture and separation existing prior to the accident. Landing gear components are under cyclic loads at every landing and during landing actions (such as braking or taxiing). According to a representative of Aerostar, the airframe manufacturer, the attachment joint failure looked like the same type of failure that a few Aerostar airplanes had in the early 1970s because of an inadequate braze joint, which allowed the landing gear to rotate. Following those failures, the manufacturer enhanced the brazing methods and performed an x-ray inspection after furnace brazing to verify that the surface braze was complete. The manufacturerwas not aware of any recent failures occurring in this area and there is not a specific inspection for this braze and further stated that, with multiple hard landings or an opposing gear collapsing, the gear could fail at the braze joint from overstress. A failure of the weld makes the airplane uncontrollable on the ground. ## Aircraft - Registration: [N90339](https://openairdocs.org/aircraft/N90339), registered now, S/N 61P-0196-015, built 1975 (OpenAirDocs) - Reported make and model: SMITH AEROSTAR601 (P) - Registry model: [Smith AEROSTAR 601P](https://openairdocs.org/model/smith-aerostar-601p) (registry code 8360608) (OpenAirDocs) - Registry engine: [Lycoming TI0-540 series](https://openairdocs.org/engine/lycoming-ti0-540-series) (registry code 41533, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 61P-0196-015 - Year built: 1975 - Airframe hours: 3069.1 - Engines: Lycoming IO-540-AA1A5 340 horsepower reciprocating; Lycoming IO-540-AA1A5 340 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, April 9, 2018 - Departed: BMC, Brigham City, UT - Destination: HCR, Heber, UT - Airport: HCR, Heber City Municipal Airport, runway 22, 6,898 × 75 ft, asphalt - Equipment: Onboard weather, Electronic multifunction display, Auto-pilot, ADS-B, Satellite tracking device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 66; injuries: none; commercial; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: class 3, with waivers/limitations; last flight review October 6, 2017; seat: left; restraint: 3-point; flight hours: 8,887 total, 1,828 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 250° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 55 °F, dew point 28 °F - Altimeter: 30.26 inHg - Observed at: K36U ## 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 20180925019239A](https://openairdocs.org/incident/20180925019239A), Sep 25, 2018: Smith AEROSTAR 601P, Heber, UT, Substantial damage. Pilot landed on touchdown markers of runway 22 at the Heber airport. The airplane proceeded down the runway for approximately 1000 feet before leaving the… ## Docket (4 files) The files NTSB released with the investigation on January 27, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=98353. 17.8 MB in all. - Materials laboratory factual report (item 1, PDF, 20 pages, 25 photos, 6.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=9937375&FileExtension=pdf&FileName=20-016%20-%20Materials%20Lab%20Factual%20Report%20(WPR18LA272)-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 11 pages, 10.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11419371&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Record of conversation (item 3, PDF, 1 page, 79 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11420172&FileExtension=pdf&FileName=Record%20of%20Conversations-Rel.pdf - Pictures of failure (item 4, PDF, 2 pages, 224 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11419463&FileExtension=pdf&FileName=Attachment%2002%20-%20Pictures%20of%20failure-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.