# NTSB CEN19LA166: Beech E90, N176TW, Greenville, TX, June 12, 2019 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: June 12, 2019, 17:25 local (22:25 UTC) - Place: Greenville, TX - Coordinates: 33.069999, -96.065277 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.0700&lon=-96.0653&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Defining event: [Takeoff: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: Federal Aviation Administration, Textron Aviation - ADs cited in the narratives: [AD 2002-01-10](https://openairdocs.org/ad/2002-01-10) (OpenAirDocs) - NTSB case key (mKey): 99616 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN19LA166 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/99616/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=99616 - Page: https://openairdocs.org/ntsb/CEN19LA166 ## Probable cause The fatigue failure of the right main landing gear upper torque knee. ## 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: [Beech E-90, 1 case](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=1152914), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01023213/cases.md) - [Landing gear system: main gear strut/axle/truck](https://openairdocs.org/ntsb-findings/01023213): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Beech E-90, 1 case](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=1152914), [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. - [Takeoff: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) (defining event); cases with it: [Beech E-90, 2 cases](https://openairdocs.org/ntsb-events/338/sequence.md?model=1152914), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) - [Landing: Abnormal runway contact](https://openairdocs.org/ntsb-events/090); cases with it: [Beech E-90, 1 case](https://openairdocs.org/ntsb-events/090/sequence.md?model=1152914), [All aircraft, 1,506 cases](https://openairdocs.org/ntsb-events/090/sequence.md) ## Analysis The pilots were performing an instructional flight with multiple takeoffs and landings when, during one takeoff, the pilots heard a loud noise, and the right main landing gear (MLG) wheel assembly departed the airplane. The pilots elected to perform an emergency landing at another airport due to its larger runways and emergency personnel and equipment. The airplane landed and came to rest upright on the runway surface. Examination of the airplane after landing revealed that the right main wheel/tire and lower shock absorber assembly departed the upper shock absorber assembly. The separated assembly, which was located near the departure airport, impacted the right horizontal stabilizer after separation, which sustained substantial damage. Metallurgical examination of the assembly revealed that the MLG fractured at the connection between the upper and lower torque knees. Fatigue was identified on a fractured piece of the upper torque knee, and other fractures on the torque knee were consistent with overload. Corrosion assisted in crack initiation, and the crack propagated through fatigue until a critical crack length was reached. It is likely that the fatigue area fractured first and the other connections experienced an increase in loading, which caused them to separate from the MLG assembly. ## Factual narrative On June 12, 2019, about 1725 central daylight time, a Beech E90 airplane, N176TW, experienced a right main landing gear (MLG) failure during takeoff from Majors Airport (GVT), Greenville, Texas, and an emergency landing was performed at Fort Worth Alliance Airport (AFW), Fort Worth, Texas. The two airline transport pilots and a company check pilot were not injured, and the airplane sustained substantial damage to the right horizontal stabilizer. The airplane was registered to Sierra American Corporation, Wilmington, Delaware, and operated by Ameristar Jet Charter, Inc., Addison, Texas, as a Title 14 Code of Federal Regulations Part 91 instructional flight. Day visual meteorological conditions prevailed at the time of the accident, and a visual flight rules flight plan was filed. The flight was originating from GVT. According to the operator, the pilots were performing an instructional flight with multiple takeoffs and landings at GVT. During the accident takeoff, the pilots heard a loud noise, and with the assistance of ground witnesses, determined the right MLG wheel assembly departed the airplane. The separated wheel assembly and fractured components were located near the runway at GVT. The pilots elected to perform an emergency landing at AFW due to large runways and emergency personnel and equipment. The airplane landed and came to rest upright on the runway surface (see Figure 1. Airplane on runway at AFW) Figure 1. Airplane on runway at AFW Examination of the airplane revealed the right main wheel/tire and lower shock absorber assembly departed the upper shock absorber assembly. The separated assembly then impacted the right horizontal stabilizer, and the stabilizer sustained substantial damage. The lower shock absorber assembly was recovered at GVT and retained for further materials examination. (See Figure 2. Right Main Wheel Assembly) Figure 2. Right Main Wheel Assembly On June 27, 2019, at Textron Aviation, Wichita, Kansas, the right MLG assembly was examined by Textron Aviation engineers under the supervision of a Federal Aviation Administration (FAA) engineer. According to the Textron engineering report, the MLG was found to have fractured at the connection between the upper and lower torque knees (part numbers 50-810032-4, 50-810295-17), and at two other connection points in the upper torque knee. The examination resulted in the following findings: 1. The upper torque knee was found to have fractured at all three connection points. 2. Fatigue was identified on a fractured piece of the upper torque knee, and all other fractures were consistent with overload. 3. Corrosion was found to have assisted in crack initiation. The crack propagated through fatigue until a critical crack length was reached. 4. Material chemistry, tensile properties, conductivity, and microstructure of the upper torque link was consistent with aluminum alloy 2014 in the T6 condition. The Textron engineering report was reviewed and approved by the NationalTransportation Safety Board materials laboratory chief engineer. According to Textron, due to historical evidence of this occurrence, a mandatory service bulletin (SB 32-3134) was released in July 1999 requiring non-destructive inspection of the torque knees at reduced intervals. Per the SB, the mandatory inspection was to be accomplished within the next 100 cycles (1 cycle = 1 landing) or next scheduled inspection for MLG torque knees with accumulated time in service of 1,000 hours. Recurring inspections were required every 1,000 cycles or 2 years, which ever occurred first. An additional service bulletin (SB 32-3116) was released in October 1999 recommending a steel torque knee replacement for the upper and lower torque knees and removed the 1,000 cycle/2-year inspection requirement for SB 32-3134. On February 22, 2002, the FAA issued airworthiness directive 2002-01-10 which required the repetitive inspection and/or replacement of the torque knees per the SBs. A review of the aircraft records revealed the upper torque knee underwent florescent penetrant inspection on March 25, 2016; airframe total time: 11,230.4/Landings 10,505, and on February 10, 2017; time and landings unknown. At the time of the accident, the airframe total time was 11,423.5 hours and 10,715 landings. ## Aircraft - Registration: [N176TW](https://openairdocs.org/aircraft/N176TW), registered now, S/N LW-76, built 1974 (OpenAirDocs) - Reported make and model: Beech E90 - Registry model: [Beech E-90](https://openairdocs.org/model/beech-e-90) (registry code 1152914) (OpenAirDocs) - Registry engine: [Pratt & Whitney Canada PT6A-60A](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-60a) (registry code 52043, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: LW-76 - Year built: 1974 - Airframe hours: 11400.4 - Engines: Pratt & Whitney PT6A-28 550 horsepower turbo prop; Pratt & Whitney PT6A-28 550 horsepower turbo prop - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: Ameristar Jet Charter, Inc. - Registered owner: Sierra American Corporation - Airworthiness certificate: Standard, Normal - Last inspection: AAIP, January 14, 2018 - Departed: GVT, Greenville, TX - Destination: AFW, Fort Worth, TX - Flight plan: VFR - Airport: AFW, Fort Worth Alliance Airport, runway 34L, 11,010 × 150 ft, concrete - Equipment: Stall warning system, Electronic flight bag or handheld device, Auto-pilot ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 64; injuries: none; flight instructor, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review February 27, 2019; seat: left; restraint: 4-point; flight hours: 7,226 total, 200 in this make and model, 4,438 as pilot in command, 11 in the last 90 days, 9 in the last 30 days - Flight instructor; age 38; injuries: none; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review March 13, 2019; seat: right; restraint: 4-point; flight hours: 8,094 total, 112 in this make and model, 5,668 as pilot in command, 32 in the last 90 days, 7 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 360° at 13 knots, gusting 21 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 61 °F - Altimeter: 29.97 inHg - Observed at: AFW ## 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 20190612018689A](https://openairdocs.org/incident/20190612018689A), Jun 12, 2019: Beech E-90, Greenville, TX, Substantial damage. During a routine training flight, touch and go operations, at Greenville TX, kgvt, upon take-off rotation, the right main landing gear departed the aircraft.… ## Docket (10 files) The files NTSB released with the investigation on November 21, 2019, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=99616. 12.7 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 6.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40478202&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Textron Materials Report (item 2, .PDF, 2.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40478203&FileExtension=.PDF&FileName=Textron%20Materials%20Report-Master.PDF - NTSB Materials Lab Email (item 3, .PDF, 883 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40478204&FileExtension=.PDF&FileName=NTSB%20Materials%20Lab%20Email-Master.PDF - Excerpt of Aircraft Records (item 4, .PDF, 648 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40478205&FileExtension=.PDF&FileName=Excerpt%20of%20Aircraft%20Records-Master.PDF - FAA Inspector Email (item 5, .PDF, 501 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40478206&FileExtension=.PDF&FileName=FAA%20Inspector%20Email-Master.PDF - Excerpt of Maintenance Manual (item 6, .PDF, 388 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40478207&FileExtension=.PDF&FileName=Excerpt%20of%20Maintenance%20Manual-Master.PDF - FAA AD 2002-01-10 (item 7, .PDF, 956 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40478208&FileExtension=.PDF&FileName=FAA%20AD%202002-01-10-Master.PDF - Textron SB 32-3134 Rev 1 (item 8, .PDF, 107 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40478209&FileExtension=.PDF&FileName=Textron%20SB%2032-3134%20Rev%201-Master.PDF - Textron SB 32-3116 (item 9, .PDF, 127 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40478210&FileExtension=.PDF&FileName=Textron%20SB%2032-3116-Master.PDF - Statement of Party Representatives to NTSB Investigation - Textron (item 10, .PDF, 224 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40478211&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation%20-%20Textron-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.