# NTSB investigations: Engine/transmission coupling NTSB aviation accident and incident investigations since 1962: the probable cause, findings, aircraft, crew, weather and docket of each, linked to the FAA registry and the FAA’s own reports. ## Latest cases - [NTSB ANC24LA017](https://openairdocs.org/ntsb/ANC24LA017.md): MD Helicopter 369E/500E · Kekaha, HI · Accident · Serious injuries · Class 3 · Limited · Final report · Feb 27, 2024 · N633JH · Substantial damage > Maintenance personnel’s noncompliance with maintenance manual procedures that required the removal of the overrunning clutch output bearing during the regreasing procedure, which resulted in inadequate regreasing of the bearing and the subsequent failure of… - [NTSB ERA23LA293](https://openairdocs.org/ntsb/ERA23LA293.md): Hughes 369D · Waldorf, MD · Accident · Minor injuries · Class 3 · Limited · Final report · Jul 9, 2023 · N5027P · Substantial damage > Fatigue failure of the overrunning clutch outer race and a subsequent inflight loss of power due to abnormal bending loads as a result of improper reassembly of the clutch subassembly following maintenance and the presence of microcracks on the clutch’s outer… - [NTSB ERA22LA256](https://openairdocs.org/ntsb/ERA22LA256.md): Robinson Helicopter R44 · North Myrtle Beach, SC · Accident · No injuries · Class 3 · Limited · Final report · May 26, 2022 · N132TC · Substantial damage > The fractured attachment lug on the forward clutch shaft yoke due to fatigue failure with multiple origins. - [NTSB ANC21LA038](https://openairdocs.org/ntsb/ANC21LA038.md): Enstrom F-28F · Palmer, AK · Accident · No injuries · Class 3 · Limited · Final report · May 9, 2021 · N8627J · Substantial damage > A loss of drive to the rotor system due to the disengagement of the main belt drive tensioning system, which resulted in a forced landing. The disengagement was due to inadequate clearance between the clutch handle and the roll pin in the handle bellcrank… - [NTSB WPR20LA228](https://openairdocs.org/ntsb/WPR20LA228.md): Md Helicopter 600 · San Andreas, CA · Accident · No injuries · Class 3 · Limited · Final report · Jul 20, 2020 · N745BW · Destroyed > The failure of the output shaft of the overrunning clutch inner race due to frictional overheating of the shaft, which resulted from the failure of the output bearing’s stainless-steel grease seal. - [NTSB ERA20LA054](https://openairdocs.org/ntsb/ERA20LA054.md): Robinson R44 · San Antonio, TX · Accident · Minor injuries · Class 3 · Limited · Final report · Dec 14, 2019 · N440AH · Substantial damage > Maintenance personnel’s failure to complete all necessary steps of a service bulletin and subsequent failure to identify the loose lower actuator bearing support bracket during inspections, which resulted in the misalignment of the clutch actuator, resulted… - [NTSB CEN19LA240](https://openairdocs.org/ntsb/CEN19LA240.md): Robinson R44 · Blair, NE · Accident · Minor injuries · Class 3 · Limited · Final report · Jul 27, 2019 · N7508Z · Substantial damage > The failure of the lower actuator bearing support bracket, which resulted in the misalignment of the clutch actuator, the loss of belt tension on the main rotor drive system, and the subsequent forced landing on sloped terrain. - [NTSB CEN19LA106](https://openairdocs.org/ntsb/CEN19LA106.md): Robinson R22 · Madill, OK · Accident · No injuries · Class 3 · Limited · Final report · Mar 20, 2019 · N7782H · Substantial damage > The failure of the V-belts due to improper maintenance, which resulted in the loss of power to the helicopter's rotor system and subsequent forced landing on rough terrain. - [NTSB ERA19FA118](https://openairdocs.org/ntsb/ERA19FA118.md): Hughes 369 · Talking Rock, GA · Accident · 1 fatal · Class 3 · Field · Final report · Mar 5, 2019 · N89ZC · Substantial damage > A fatigue failure of the overrunning clutch subassembly due to abnormal bending loads due to cracks on the center engine mount, which resulted in an inflight loss of power. Contributing to the accident was the helicopter's low altitude and airspeed when the… - [NTSB CEN18LA334](https://openairdocs.org/ntsb/CEN18LA334.md): Schweizer 269C · Kindred, ND · Accident · No injuries · Class 3 · Limited · Final report · Aug 16, 2018 · N3625Z · Destroyed > The pilot’s failure to adequately inspect the lower coupling driveshaft during his preflight inspection and his non-compliance with an applicable airworthiness directive, which resulted in the failure of the forward drive splines of the lower coupling… - [NTSB WPR18FA088](https://openairdocs.org/ntsb/WPR18FA088.md): Hastings Thomas G Cirrus VK 30 · Agua Dulce, CA · Accident · 4 fatal · Field investigation · Final report · Feb 11, 2018 · N52TH · Substantial damage > The driveshaft fracture due to overstress loading and rotational bending as a result of the under-torqued nuts on the elastomeric couplings backing off and the subsequent in-flight separation of the horizontal fairing due to contact with the separated end of… - [NTSB WPR17LA113](https://openairdocs.org/ntsb/WPR17LA113.md): Bell 206B · Rockville, ID · Accident · Serious injuries · Limited investigation · Final report · May 26, 2017 · N24FS · Substantial damage > The in-flight failure of the engine-to-transmission drive shaft due to a fatigue fracture of one of the KAflex flex frames caused by a loose bolt, which resulted in a total loss of engine power and a subsequent hard landing. - [NTSB WPR16FA072](https://openairdocs.org/ntsb/WPR16FA072.md): Bell 206B · Honolulu, HI · Accident · 1 fatal · Field investigation · Final report · Feb 18, 2016 · N80918 · Substantial damage > The in-flight failure of the engine-to-transmission drive shaft due to improper maintenance, which resulted in low main rotor rpm and a subsequent hard landing to water. - [NTSB CEN16LA105](https://openairdocs.org/ntsb/CEN16LA105.md): Enstrom TH-180 · Menominee, MI · Accident · No injuries · Limited investigation · Final report · Feb 12, 2016 · N180TH · Substantial damage > The failure of the torque meter mounting bolts, which resulted in a loss of engine power to the main drive belt and rotors. - [NTSB CEN15LA396](https://openairdocs.org/ntsb/CEN15LA396.md): Burns Mini 500 · Butler, MO · Accident · No injuries · Limited investigation · Final report · Aug 21, 2015 · UNREG · Substantial damage > The pilot's failure to attain a proper landing flare following an autorotation for reasons that could not be determined based on available information. - [NTSB CEN15CA155](https://openairdocs.org/ntsb/CEN15CA155.md): Gaddis Michael Exec 162 F · Plymouth, IN · Accident · No injuries · Data collection · Final report · Feb 26, 2015 · N123XZ · Substantial damage > The failure of the helicopter's main drive belt resulting in the pilot performing a forced landing, during which the helicopter's fuselage was substantially damage. - [NTSB WPR15LA109](https://openairdocs.org/ntsb/WPR15LA109.md): Bell/Garlick UH 1H · Shelton, WA · Accident · No injuries · Limited investigation · Final report · Feb 19, 2015 · N166DR · Substantial damage > The fatigue failure of the engine-to-transmission driveshaft adapter attachment bolt due to the application of inadequate torque on the bolt during assembly. - [NTSB ERA14LA099](https://openairdocs.org/ntsb/ERA14LA099.md): Bell 47D1 · Pell City, AL · Accident · Minor injuries · Limited investigation · Final report · Jan 21, 2014 · N93067 · Substantial damage > The pilot’s use of an improper clutch engagement procedure, which resulted in clutch glazing, slippage, and, ultimately, the in-flight disengagement of the clutch and a loss of rotor rpm. Contributing to the accident were the installation of a light-weight… - [NTSB WPR14LA062](https://openairdocs.org/ntsb/WPR14LA062.md): Hiller UH 12E · Chowchilla, CA · Accident · No injuries · Limited investigation · Final report · Dec 9, 2013 · N36MV · Substantial damage > The failure of the torsional drive coupling, which resulted in a loss of drive to the main rotor system during low-altitude flight. - [NTSB CEN12LA228](https://openairdocs.org/ntsb/CEN12LA228.md): Enstrom 280FX · Corpus Christi, TX · Accident · Minor injuries · Limited investigation · Final report · Apr 3, 2012 · N3042D · Substantial damage > The failure of the bolt that retained the clutch drive rod end, which resulted in a loss of main rotor drive and a subsequent hard landing. - [NTSB ERA11LA204](https://openairdocs.org/ntsb/ERA11LA204.md): Robinson R22 · Goshen, NY · Accident · No injuries · Limited investigation · Final report · Mar 22, 2011 · N259TW · Substantial damage > The pilot’s failure to adhere to published preflight checklist limitations and procedures, resulting in excessive slack and subsequent failure of the power transmission belts and a total loss of rotor system drive. - [NTSB WPR11LA167](https://openairdocs.org/ntsb/WPR11LA167.md): Rotorway A600 · Chandler, AZ · Accident · No injuries · Limited investigation · Final report · Mar 15, 2011 · N602RW · Substantial damage > A design modification that changed the fasteners and components used to attach the main rotor drive pulley to the engine, which resulted in fatigue failure of those fasteners and a complete loss of power to the main rotor. - [NTSB WPR10FA112](https://openairdocs.org/ntsb/WPR10FA112.md): Eurocopter AS350 B3 · Reno, NV · Accident · No injuries · Field investigation · Final report · Jan 17, 2010 · N904CF · Substantial damage > The improper installation of the engine-to-main gear box flex coupling, which resulted in the failure of the flex coupling and a loss of power to the rotor system during takeoff. Contributing to the accident was the mechanic who removed the engine's failure… - [NTSB ANC08FA053](https://openairdocs.org/ntsb/ANC08FA053.md): Eurocopter AS 350 B2 · Chickaloon, AK · Accident · 4 fatal · Field investigation · Final report · Apr 15, 2008 · N213EH · Substantial damage > An in-flight overtorque of the engine-to-transmission driveshaft resulting in disconnection of the main transmission from the engine. The overtorque likely occurred due to an in-flight main rotor blade contact with snow-covered terrain, precluding significant… ## The whole list in SQL Runs in DuckDB 1.2 or later on the release's Parquet files over HTTPS: ```sql SELECT c."ntsbNumber", c."eventDate", c."eventType", c."eventCity", c."eventStateOrRegion", a.n_number, a."aircraftMake", a."aircraftModel", c."highestInjuryLevel", c."totalFatal", c."completionStatus", c.report_url FROM 'https://openairdocs.org/data/latest/ntsb_case_detail.parquet' c LEFT JOIN 'https://openairdocs.org/data/latest/ntsb_aircrafts.parquet' a ON a.case_mkey = c."mKey" AND a.position = 1 WHERE c."mKey" IN (SELECT f.case_mkey FROM 'https://openairdocs.org/data/latest/ntsb_findings.parquet' f WHERE starts_with(f."findingCode", '01046310')) ORDER BY c."eventDate" DESC, c."ntsbNumber" DESC ``` This list as a web page: https://openairdocs.org/ntsb-findings/01046310/cases --- 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.