# NTSB CEN17LA324: Piper PA 18-150, N82912, Sweetwater, TX, August 18, 2017 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 18, 2017, 11:45 local (16:45 UTC) - Place: Sweetwater, TX - Coordinates: 32.471668, -100.469169 - Nearby events: https://openairdocs.org/map.md?lat=32.4717&lon=-100.4692&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-flare/touchdown: Hard landing](https://openairdocs.org/ntsb-events/092) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report September 14, 2020 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Federal Aviation Administration, Lubbock FSDO, USDA/ APHIS/ Wildlife Services - NTSB case key (mKey): 95864 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN17LA324 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/95864/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=95864 - Page: https://openairdocs.org/ntsb/CEN17LA324 ## Probable cause The pilot's improper landing flare, which resulted in a hard landing and the overstress failure of the right main landing gear. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Performance/control parameters: landing flare](https://openairdocs.org/ntsb-findings/01062041): Aircraft › Aircraft oper/perf/capability · Incorrect use/operation (probable cause); cases with it: [Piper PA-18-150, 8 cases](https://openairdocs.org/ntsb-findings/01062041/cases.md?model=7101828), [All aircraft, 1,285 cases](https://openairdocs.org/ntsb-findings/01062041/cases.md) - [Landing gear system: main landing gear](https://openairdocs.org/ntsb-findings/01023210): Aircraft › Aircraft systems · Capability exceeded (probable cause); cases with it: [Piper PA-18-150, 2 cases](https://openairdocs.org/ntsb-findings/01023210/cases.md?model=7101828), [All aircraft, 241 cases](https://openairdocs.org/ntsb-findings/01023210/cases.md) - [Landing gear system: main landing gear](https://openairdocs.org/ntsb-findings/01023210): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Piper PA-18-150, 2 cases](https://openairdocs.org/ntsb-findings/01023210/cases.md?model=7101828), [All aircraft, 241 cases](https://openairdocs.org/ntsb-findings/01023210/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Piper PA-18-150, 160 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=7101828), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/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: Hard landing](https://openairdocs.org/ntsb-events/092) (defining event); cases with it: [Piper PA-18-150, 10 cases](https://openairdocs.org/ntsb-events/092/sequence.md?model=7101828), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) - [Landing-flare/touchdown: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330); cases with it: [Piper PA-18-150, 4 cases](https://openairdocs.org/ntsb-events/330/sequence.md?model=7101828), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Landing-flare/touchdown: Loss of control on ground](https://openairdocs.org/ntsb-events/230); cases with it: [Piper PA-18-150, 109 cases](https://openairdocs.org/ntsb-events/230/sequence.md?model=7101828), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) - [Landing-flare/touchdown: Landing gear collapse](https://openairdocs.org/ntsb-events/094); 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 of the tailwheel-equipped airplane stated that he intended to make a wheel landing with the flaps fully extended following the positioning flight. He stated that he felt a "little bump" shortly after the airplane touched down on the right main landing gear (MLG), and the airplane began to swerve left. The pilot reported that he was unable to regain directional control with full right rudder and right brake inputs. The airplane continued to swerve left and departed the left runway edge; the right MLG collapsed after it entered soft terrain. The airplane came to rest heading about 180° opposite the intended runway heading. The airplane sustained substantial damage to the right wing, both main wing spars, and the right elevator. Postaccident examination of the airplane revealed several damaged MLG components. Laboratory examination of the damaged MLG components did not identify any evidence of preexisting damage or cracks. The damaged MLG brace tubes and the piston inside the right hydrasorb shock unit had fractured from overstress. The overall damage to the MLG was consistent with a hard landing. It is likely that the internal piston shaft of the right hydrasorb shock unit failed first in bending overstress during the hard landing, which was followed by the overstress failure of both the left and right MLG brace tubes. ## Factual narrative On August 18, 2017, about 1145 central daylight time, a Piper PA-18-150 airplane, N82912, was substantially damaged while landing at Avenger Field Airport (SWW), Sweetwater, Texas. The commercial pilot and his passenger were not injured. The airplane was registered to and operated by the United States Department of Agriculture (USDA) as a public aircraft.The pilot reported that he chose to land on runway 17 at SWW because the automated weather observing system at the airport indicated the surface wind was 9 knots from the south-southwest. The pilot stated that he intended to make a wheel landing with the flaps fully extended. He stated that he felt a "little bump" shortly after the airplane touched down on the right main landing gear (MLG), and the airplane began to swerve left. The pilot reported that he was unable to regain directional control with full right rudder and right brake inputs. The airplane continued to swerve left and departed the left runway edge where the right MLG collapsed after it entered soft terrain. The airplane came to rest on a north heading. The airplane sustained substantial damage to the right wing, both main wing spars, and the right elevator. The Federal Aviation Administration inspector who examined the wreckage identified several fractured MLG components, which were subsequently submitted to the National Transportation Safety Board Materials Laboratory for additional examination. The left-side MLG hydrasorb shock unit was intact with its external shock cord rings wrapped around its tee flanges. The left MLG brace tube was bent and fractured near where it attached to the left hydrasorb shock unit. Adjacent to the fracture surface, the brace tube exhibited local thinning or necking. The tube fracture surface exhibited either a cup-shaped morphology, or a flat orientation angled at about 45° relative to the tube direction. The observed fracture features and tube damage were consistent with tensile overstress. There was no evidence of preexisting cracks or damage to the left MLG brace tube or its associated hydrasorb shock unit. The right-side MLG brace tube had buckled and was partially fractured about 5.75 inches from the fitting hole. The fracture surface exhibited a general rough texture with a dull luster, which was consistent with tensile overstress. Additionally, the opposite end of the right MLG brace tube had buckled inward toward the partial fracture. The observed brace tube damage was consistent with bending overstress. The right-side MLG hydrasorb shock unit exhibited a fracture of its internal piston shaft. The piston shaft had bent downward adjacent to the fracture surface. One side of the fracture exhibited a generally flat surface on one half before it transitioned to a 45° shear lip. Additional examination of the fracture with a scanning electron microscope revealed dimple rupture in a slanted orientation. The observed fracture features and damage to the internal piston shaft were consistent withbending overstress. There was no evidence of preexisting cracks or damage to the internal piston shaft. The chemical composition, microstructure, and measured material hardness were consistent with a martensitic precipitation-hardened stainless-steel alloy. ## Aircraft - Registration: [N82912](https://openairdocs.org/aircraft/N82912), registered now, S/N 18-7709195, 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: 18-7709195 - Year built: 1977 - Airframe hours: 10623.9 - Engines: Lycoming O-360-C4P 180 horsepower reciprocating - Damage: Substantial damage - Flight: Public aircraft - federal, Public use - Operator: Usda-Aphis-Ws - Registered owner: Usda-Aphis-Ws - Airworthiness certificate: Standard, Normal - Last inspection: Annual, July 5, 2017, 46 hours before - Departed: SNK, Winston Field, TX - Destination: SWW, Sweetwater, TX - Flight plan: Company VFR - Airport: SWW, Avenger Field Airport, runway 17, 5,840 × 100 ft, asphalt - Equipment: Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 57; injuries: none; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review April 4, 2017; seat: front; restraint: 4-point; flight hours: 10,245 total, 10,163 in this make and model, 10,070 as pilot in command, 58 in the last 90 days, 36 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 230° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: 8,000 ft broken - Temperature: 84 °F, dew point 68 °F - Altimeter: 30.15 inHg - Observed at: SWW ## 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 20170818010399A](https://openairdocs.org/incident/20170818010399A), Aug 18, 2017: Piper PA-18-150, Sweetwater, TX, Substantial damage. On August 18, 2017, at 1145 local time, N82912, a Piper PA-18-150 super-cub, registered to united states department of agriculture ground looped while landing.… ## Docket (4 files) The files NTSB released with the investigation on July 8, 2020, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=95864. 5.8 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 904 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40485176&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Materials Laboratory Factual Report (item 2, .PDF, 4.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40485177&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report-Master.PDF - Weather Reports (item 3, .PDF, 101 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40485178&FileExtension=.PDF&FileName=Weather%20Reports-Master.PDF - Photos (item 4, .PDF, 672 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40485179&FileExtension=.PDF&FileName=Photos-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.