# NTSB WPR21LA117: Piper PA-44-180, N125MG, Redmond, OR, February 7, 2021 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: February 7, 2021, 14:00 local (22:00 UTC) - Place: Redmond, OR - Coordinates: 44.254102, -121.15058 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=44.2541&lon=-121.1506&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: 3 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: FAA FSDO - NTSB case key (mKey): 102669 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR21LA117 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/102669/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=102669 - Page: https://openairdocs.org/ntsb/WPR21LA117 ## Probable cause Failure of the landing gear strut piston tube due to fatigue cracking from corrosion pitting. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: main landing gear](https://openairdocs.org/ntsb-findings/01023210): Aircraft › Aircraft systems · Fatigue/wear/corrosion (probable cause); cases with it: [Piper PA-44-180, 3 cases](https://openairdocs.org/ntsb-findings/01023210/cases.md?model=7104402), [All aircraft, 241 cases](https://openairdocs.org/ntsb-findings/01023210/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-44-180, 11 cases](https://openairdocs.org/ntsb-events/094/sequence.md?model=7104402), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) ## Analysis During the instructional flight, the right main landing gear separated during landing roll following a normal touchdown. The separated right landing gear assembly then struck the rear edge of the wing, which resulted in substantial damage to the wing. Examination revealed that the right landing gear strut piston tube had failed due to two fatigue cracks that had originated from corrosion pits near a drilled hole. Two months before the accident, the manufacturer had issued a service letter applicable to the airplane that called for inspection of the strut piston tube for fatigue cracks. Performance of the inspection called for in the service letter would have discovered the cracks that led to the accident. Although the operator held a Part 141 certificate, they were not required to comply with the service letter. ## Factual narrative On February 7, 2021, about 1400 Pacific standard time, a Piper PA-44-180 airplane, N125MG, was substantially damaged when it was involved in an accident at Roberts Field Airport (RDM), Redmond, Oregon. The flight instructor and two pilots receiving instruction were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 141 instructional flight. According to the flight instructor, this was an instructional flight with one of the two pilots receiving instruction flying and the other observing. They had performed multiple takeoffs and landings before the accident. On the accident landing, the pilot receiving instruction flew a stabilized approach to a touchdown followed by a smooth deceleration. While on the rollout, the flight instructor took the controls, felt a pull to the right, and thought it might be a flat tire. He worked to maintain directional control; however, the right wing continued to sink. The right main landing gear separated from the wing and struck the rear of the wing, which resulted in substantial damage to the wing. A postflight inspection by the operator’s maintenance personnel revealed the strut piston tube, a component of the right main landing gear strut assembly, had fractured, which allowed the right main landing gear to separate from the wing. Examination of the components of the landing gear strut assembly at the National Transportation Safety Board’s (NTSB’s) Materials Laboratory revealed two thumbnail-shaped fatigue cracks on the strut piston tube that had originated from corrosion pits near a drilled hole. One crack was 0.21 inch in length, and the other was 0.33 inch in length. Both encompassed maximum widths equivalent to the piston wall thickness of 0.125 inch. The airplane’s most recent annual inspection was completed on November 7, 2020, and it had accumulated 11,614.5 hours at that time. The operator reported that at the time of the accident, the airplane had accumulated 11,769.5 hours and that this was also the time in service of the failed strut piston tube. On December 23, 2020, Piper Aircraft Incorporated published Service Letter 1263, applicable to the PA-44-180 and titled “Main Landing Gear Piston Tube Inspection.” The compliance time section of the service letter stated in part: Initial inspection: For airplanes with main landing gear strut assemblies that have 6,500 hours or more time in service (TIS), and airplanes with an unknown service history of the main landing gear strut assemblies, initial inspection is to occur at the next regularly scheduled maintenance event, but not to exceed the next 100 hours TIS. The purpose section of the service letter stated in part: A review of service history reveals that fatigue cracks can develop in the main landing gear of the affected airplanes; specifically, at the bolt hole in the piston tube common to the fork. Review of the diagrams in the service letter revealed that the fatigue cracks found on the airplane’s piston tube were inthe specific area called out for inspection by the service letter. According to the director of maintenance, as the holder of a Part 141 certificate, the operator was not obligated to comply with service letters. He indicated that they did strive to be aware of all service information and did comply with most service directives. Regarding Service Letter 1263, he stated that the information from the manufacturer was new, and they had not incorporated it into their maintenance program before the accident. Following the accident, they did incorporate the repetitive inspection called for in the service letter. ## Aircraft - Registration: [N125MG](https://openairdocs.org/aircraft/N125MG), registered now, S/N 4496152, built 2002 (OpenAirDocs) - Reported make and model: PIPER PA-44-180 - Registry model: [Piper PA-44-180](https://openairdocs.org/model/piper-pa-44-180) (registry code 7104402) (OpenAirDocs) - Registry engine: [Lycoming O-360 series](https://openairdocs.org/engine/lycoming-o-360-series) (registry code 41575, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 4496152 - Year built: 2002 - Airframe hours: 11615 - Engines: LYCOMING O-360 SERIES 180 horsepower reciprocating; LYCOMING O-360 SERIES 180 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Registered owner: Hillsboro Aero Academy LLC - Airworthiness certificate: Standard, Normal - Last inspection: Annual, November 7, 2020 - Destination: Same as departure - Airport: RDM, Roberts Fld, runway 11/29, 7,006 × 100 ft, asphalt - Equipment: Electronic primary flight display, ADS-B, Electronic flight bag or handheld device, Electronic multifunction display ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 33; injuries: none; flight instructor, commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review December 22, 2020; seat: right; restraint: 3-point; flight hours: 563 total, 65 in this make and model, 494 as pilot in command, 127 in the last 90 days, 52 in the last 30 days, 3 in the last 24 hours - Pilot; age 22; injuries: none; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, without waivers/limitations; last flight review January 19, 2021; seat: left; restraint: 3-point; flight hours: 165 total, 10 in this make and model, 31 in the last 90 days, 14 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 270° at 13 knots, gusting 17 - Visibility: 8 statute miles - Observed at: RDM, 0.5 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 20210207001499A](https://openairdocs.org/incident/20210207001499A), Feb 7, 2021: Piper PA-44-180, Redmond, OR, Substantial damage. Aircraft was practicing touch and go?s. the crew described the landings as normal, no hard landings, and there were no strong cross winds during the time of… ## Docket (6 files) The files NTSB released with the investigation on August 10, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=102669. 17.0 MB in all. - Materials laboratory factual report (item 1, PDF, 19 pages, 29 photos, 13.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12563717&FileExtension=pdf&FileName=21-048%20-%20Materials%20Lab%20Factual%20Report%20(WPR21LA117)-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 9 pages, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12470712&FileExtension=pdf&FileName=NTSB%20Form%206120%20N125MG_redacted-Rel.pdf - Pilot's statement (item 3, PDF, 2 pages, 160 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13403514&FileExtension=pdf&FileName=Pilot%20Incident%20Statement_N125MG_KRDM-Rel.pdf - Piper service letter 1263 (item 4, PDF, 5 pages, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14225691&FileExtension=pdf&FileName=SL_1263-Rel.pdf - Memo for record email summary from dom (item 5, PDF, 2 pages, 179 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13572536&FileExtension=pdf&FileName=Memo%20for%20Record%20EMail%20from%20DoM%20Summary-Rel.pdf - Photos (item 6, PDF, 2 pages, 168 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14225419&FileExtension=pdf&FileName=Photos%20for%20WPR21LA117-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.