# NTSB CEN20LA175: Beech 1900, N31704, San Antonio, TX, May 9, 2020 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: May 8, 2020, 20:50 local (May 9, 2020, 01:50 UTC) - Place: San Antonio, TX - Coordinates: 29.523611, -98.469444 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=29.5236&lon=-98.4694&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing: 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: Central Region - Parties: Textron Aviation, FAA San Antonio FSDO, Ameriflight - NTSB case key (mKey): 101261 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN20LA175 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/101261/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=101261 - Page: https://openairdocs.org/ntsb/CEN20LA175 ## Probable cause The failure of the left main landing gear upper drag leg arm due to substandard mechanical properties, which resulted in a collapse of the landing gear upon landing. ## 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 · Failure (probable cause); cases with it: [Beech 1900C, 1 case](https://openairdocs.org/ntsb-findings/01023210/cases.md?model=1154161), [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: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330); cases with it: [Beech 1900C, 2 cases](https://openairdocs.org/ntsb-events/330/sequence.md?model=1154161), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Landing: Landing gear collapse](https://openairdocs.org/ntsb-events/094) (defining event); cases with it: [Beech 1900C, 2 cases](https://openairdocs.org/ntsb-events/094/sequence.md?model=1154161), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) - [Landing: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490); cases with it: [Beech 1900C, 1 case](https://openairdocs.org/ntsb-events/490/sequence.md?model=1154161), [All aircraft, 1,309 cases](https://openairdocs.org/ntsb-events/490/sequence.md) ## Analysis During the cargo flight’s initial climb, the landing gear did not retract when the landing gear handle was raised. The pilot attempted to cycle the landing gear handle once more, which yielded the same result. Following the second unsuccessful gear retraction, the pilot elected to leave the landing gear handle in the DOWN position and continued to the destination. Prior to landing the pilot completed the before landing checklist and noted three green lights and no red lights, which indicated the landing gear was down, locked, and safe for landing. The airplane touched down on the runway and the left main landing gear collapsed, the red unsafe light in the landing gear handle illuminated and was followed by an aural horn indicating the landing gear was now unlocked and unsafe for landing. Simultaneously, the airplane began to dip toward the left, causing the left-wing tip to contact the runway. The airplane exited the runway, resulting in substantial damage to the left wing. A postaccident examination revealed that the left main landing gear upper drag leg arm fractured in bending and twisting overload. There was no evidence of preexisting cracking or corrosion. The dimensions of the part were consistent with the drawing and the chemical composition and microstructure were consistent with 7075 aluminum alloy, as required. The mechanical properties were lower, and the electrical conductivity was higher than the requirements for 7075-T6 aluminum alloy. The measured mechanical properties and electrical conductivity did not conform to any standard temper for 7075 aluminum alloy. A review of the operator’s maintenance records revealed that several months prior to the accident, the left main landing gear drag brace assembly was replaced on the airplane because it was due for overhaul. The left main landing gear drag brace assembly installed was the unit removed after the accident. The drag brace assembly had been overhauled by the operator. Based on the paperwork, the overhaul work performed did not interfere with the mechanical properties of the upper drag leg arm. The failure of the left main landing gear upper drag leg arm during the touchdown resulted in a collapse of the gear and the left wing’s subsequent contact with terrain. The failure of the upper drag arm was the result of substandard mechanical properties. ## Factual narrative On May 8, 2020, about 2050 central daylight time, a Beechcraft 1900C airplane, N31704, sustained substantial damage when it was involved in an accident near San Antonio, Texas. The pilot sustained no injury. The airplane was operated as a Title 14 Code of Federal Regulations Part 135 cargo flight, as Ameriflight 1829. The operator reported that the flight departed the Corpus Christi International Airport (CRP), Corpus Christi, Texas, at 2004, with 631 lbs of cargo, and a fuel load of 2,800 lbs. During the initial climb, the captain selected the landing gear handle to the UP position to retract the landing gear. The attempt was unsuccessful, and the captain attempted to cycle the landing gear handle once more, which yielded the same result. Following the second unsuccessful gear retraction, the captain elected to leave the landing gear handle in the DOWN position and continued to the San Antonio International Airport (SAT), San Antonio, Texas, where more services would be available if needed. At SAT, air traffic control cleared the airplane for the visual approach. The pilot entered a right base leg and completed the before landing checklist, noting three green lights and no red lights, which indicated the landing gear was down, locked, and safe for landing. The airplane touched down, about 90 kts, around the aiming point marker on runway 4. As the main landing gear touched down on the dry concrete, the left main landing gear collapsed, the red unsafe light in the landing gear handle illuminated, and was followed by an aural horn, indicating the landing gear was now unlocked and unsafe for landing. Simultaneously, the airplane began to dip toward the left, causing the left-wing tip to contact the runway. The pilot reported there was no side loading during the touchdown. The airplane subsequently exited the runway and came to a stop. The left wing sustained substantial damage from the accident sequence. The airplane was lifted after the accident to allow the left main landing gear to be manually extended and pinned in place. The upper drag leg arm was found fractured, and the actuator forward rod end was bent. The left main landing gear drag brace assembly (Beech part number 114-810023-1, serial number ARC31209-5) and the left main landing gear actuator (Beech part number 114-380041-21, APPH part number 40600-12, serial number 14) were retained for further examination. A postaccident examination revealed that the upper drag leg arm fractured in bending and twisting overload. There was no evidence of pre-existing cracking or corrosion. The dimensions of the part were consistent with the drawing and the chemical composition and microstructure were consistent with 7075 aluminum alloy as required. The mechanical properties were lower, and the electrical conductivity was higher than the requirements for 7075-T6 aluminum alloy. The measured mechanical properties and electrical conductivity did not conform to any standard temper for 7075 aluminum alloy.A review of the operator’s maintenance records revealed that on April 29, 2020, the left main landing gear and right main landing gear drag brace assemblies were replaced on the airplane because they were due for overhaul. The left main landing gear drag brace assembly installed was the unit removed after the accident (serial number ARC31209-5). The drag brace assembly had been overhauled by Ameriflight in February 2020. Based on the paperwork, the overhaul entailed disassembly, stripping of paint, inspection, repaint, and reassembly with new hardware. A postaccident functional test of the left main landing gear actuator found no anomalies. A postaccident laboratory analysis of a sample of the airplane’s hydraulic fluid found no anomalies. A review of the operator’s cargo load manifest showed that the airplane was within weight and balance limitations for the flight. The airplane was not equipped with a cockpit voice recorder or flight data recorder, nor was it required to be. ## Aircraft - Registration: [N31704](https://openairdocs.org/aircraft/N31704), registered now, S/N UB-12, built 1984 (OpenAirDocs) - Reported make and model: Beech 1900 (C) - Registry model: [Beech 1900C](https://openairdocs.org/model/beech-1900c) (registry code 1154161) (OpenAirDocs) - Registry engine: [Pratt & Whitney Canada PT6A-65B](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-65b) (registry code 52115, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: UB-12 - Year built: 1984 - Airframe hours: 41114.2 - Engines: Pratt & Whitney Canada PT6A-65B 1173 horsepower turbo prop; Pratt & Whitney Canada PT6A-65B 1173 horsepower turbo prop - Damage: Substantial damage - Flight: Part 135 - Operator: Ameriflight, LLC, doing business as Ameriflight - Registered owner: UAS Transervices, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: AAIP, May 4, 2020 - Departed: CRP, Corpus Christi, TX - Destination: SAT, San Antonio, TX - Flight plan: IFR - Airport: SAT, San Antonio Intl, runway 04, 8,505 × 150 ft, concrete - Equipment: Stall warning system, ADS-B, Electronic flight bag or handheld device, Auto-pilot ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 68; injuries: none; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review May 7, 2020; seat: left; restraint: 4-point; flight hours: 25,358 total, 944 in this make and model, 26,293 as pilot in command, 83 in the last 90 days, 29 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Night - Wind: 20° at 13 knots, gusting 20 - Visibility: 10 statute miles - Lowest ceiling: 25,000 ft broken - Temperature: 73 °F, dew point 50 °F - Altimeter: 30.06 inHg - Observed at: KSAT, 1 nm away - METAR: KSAT 090151Z 02013G20KT 350V050 10SM FEW060 BKN250 23/10 A3006 RMK AO2 SLP161 T02280100 ## 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 20200508005619A](https://openairdocs.org/incident/20200508005619A), May 8, 2020: Beech 1900C, San Antonio, TX, Substantial damage. N31704 a Beech 1900C on may 8, 2020 was on a flight from corpus christie, TX (kcrp) to San Antonio, TX (ksat). After departure from kcrp landing gear failed to… ## Docket (10 files) The files NTSB released with the investigation on March 10, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=101261. 34.4 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13095538&FileExtension=pdf&FileName=NTSB%20Form%206120_1%20Redacted-Rel.pdf - Accident photographs (item 2, PDF, 6 pages, 2.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13095637&FileExtension=pdf&FileName=Accident%20Photographs-Rel.pdf - N31704 Beech 1900C ADS-B tabular data (.xlsx file) (item 3, XLSX, 3.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13095730&FileExtension=xlsx&FileName=N31704%20Beech%201900C%20ADS-B%20Tabular%20Data-Rel.xlsx - N31704 Beech 1900C ADS-B google earth data (.kmz file) (item 4, KMZ, 169 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13095558&FileExtension=kmz&FileName=N31704%20Beech%201900C%20ADS-B%20Google%20Earth%20Data-Rel.kmz - Structures group chairman's factual report (item 5, PDF, 5 pages, 1 photo, 482 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13006396&FileExtension=pdf&FileName=CEN20LA175%20Structures%20Factual-Rel.pdf - Structures group chairman's factual report appendix a-maintenance records (item 6, PDF, 16 pages, 4.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13006542&FileExtension=pdf&FileName=CEN20LA175%20Structures%20Appendix%20A-Mx%20Records_Redacted-Rel.pdf - Structures group chairman's factual report appendix b-textron m&p report (item 7, PDF, 18 pages, 26 photos, 5.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13006893&FileExtension=pdf&FileName=CEN20LA175%20Structures%20Appendix%20B-Textron%20M%26P%20Report_Redacted-Rel.pdf - Structures group chairman's factual report appendix c-actuator exam (item 8, PDF, 6 pages, 4.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13006755&FileExtension=pdf&FileName=CEN20LA175%20Structures%20Appendix%20C-Actuator%20Exam_Redacted-Rel.pdf - Additional documents (item 9, PDF, 10 pages, 9.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13095548&FileExtension=pdf&FileName=Additional%20Documents%20Redacted-Rel.pdf - NTSB party member forms (item 10, PDF, 3 pages, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13095720&FileExtension=pdf&FileName=NTSB%20Party%20Member%20Forms%20Redacted-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.