# NTSB ERA13LA390: Continental Copters 47G, N6356X, Sandy Hook, KY, August 31, 2013 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 31, 2013, 09:50 local (13:50 UTC) - Place: Sandy Hook, KY - Coordinates: 38.085556, -83.130279 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=38.0856&lon=-83.1303&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Defining event: [Approach-VFR pattern final: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report December 5, 2013 - Report: Approved by Office Director - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO - NTSB case key (mKey): 87929 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA13LA390 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/87929/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=87929 - Page: https://openairdocs.org/ntsb/ERA13LA390 ## Probable cause The in-flight disengagement of the tail rotor extension shaft from the tail rotor gearbox, resulting in a loss of tail rotor control. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Tail rotor drive system: tail rotor drive shaft](https://openairdocs.org/ntsb-findings/01046510): Aircraft › Aircraft propeller/rotor · Damaged/degraded (probable cause); cases with it: [Continental Copters 47G, 1 case](https://openairdocs.org/ntsb-findings/01046510/cases.md?model=2390105), [All aircraft, 25 cases](https://openairdocs.org/ntsb-findings/01046510/cases.md) - [Performance/control parameters: yaw control](https://openairdocs.org/ntsb-findings/01062024): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [Continental Copters 47G, 1 case](https://openairdocs.org/ntsb-findings/01062024/cases.md?model=2390105), [All aircraft, 149 cases](https://openairdocs.org/ntsb-findings/01062024/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Approach-VFR pattern final: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Continental Copters 47G, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=2390105), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Autorotation: Hard landing](https://openairdocs.org/ntsb-events/092); cases with it: [Continental Copters 47G, 1 case](https://openairdocs.org/ntsb-events/092/sequence.md?model=2390105), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) ## Analysis The pilot reported that as he approached a pre-planned landing zone, he reduced engine power for landing. The helicopter yawed to the right, then back to the left. The helicopter yawed again, and the pilot felt unusual vibrations, so he decided to perform an autorotation. The helicopter landed hard on a gravel road and sustained substantial damage. Examination of the wreckage revealed impact damage to the aft tail boom from main rotor contact. The aft-most section of the tail rotor drive shaft was missing and was not recovered. It is likely that, during the hard landing, a main rotor blade struck the tail boom and liberated the drive shaft section. Manipulation of the tail rotor shaft input at the tail rotor gearbox revealed a lack of continuity to the tail rotor hub and blades. The tail rotor did not rotate when the universal joint, located at the forward end of the extension housing tube, was turned. Subsequent examination showed that the tail rotor gearbox was operational; however, the tail rotor extension shaft was found disconnected from the input coupling to the tail rotor gearbox. Rotational scoring inside the extension shaft housing indicated excessive play in the shaft that was present before the accident, which would have resulted in the loss of tail rotor control. ## Factual narrative On August 31, 2013, about 0950 eastern daylight time, Continental Copters, Inc. 47G, N6356X, was substantially damaged during a forced landing near Sandy Hook, Kentucky. The commercial pilot and one passenger were not injured. The helicopter was registered to Sierra Aeronautics LLC and was operated by the pilot under the provisions of 14 Code of Regulations Part 91 as a positioning flight. Day, visual meteorological conditions prevailed and no flight plan was filed. The flight originated at Morehead, Kentucky (M97) about 0930. As the helicopter was established in the traffic pattern for landing at a pre-established landing zone, at 300 feet above ground level (AGL), the pilot turned onto final and made a power reduction. The helicopter began to yaw to the right, and then back to the left. The pilot raised the collective and the helicopter yawed again to the right and the pilot felt unusual vibrations. The pilot then attempted an autorotation. He avoided a tree and a parked car and the helicopter landed hard on a gravel road. An inspector with the Federal Aviation Administration responded to the accident site and inspected the wreckage. There was evidence of main rotor contact with the aft section of the tail boom. The tail boom and main rotor blades sustained structural damage. The most aft section of the tail rotor drive shaft was missing; a search of the area failed to locate the missing component. Manipulation of the tail rotor shaft input at the tail rotor gearbox revealed a lack of continuity to the tail rotor hub and blades. When the universal joint, located at the forward end of the extension housing tube, was turned, the tail rotor did not rotate. Disassembly of the tail rotor gear box revealed that the internal gears were normal in appearance and well lubricated. The tail rotor extension shaft was found disconnected from the input coupling to the tail rotor gear box. The splined end on the aft section of the shaft exhibited signatures of overheating and rotation while out of the input coupling. There were scoring marks inside the extension housing tube, indicative of excessive play in the shaft and center bearing housing. ## Aircraft - Registration: [N6356X](https://openairdocs.org/aircraft/N6356X), registered now, S/N CCI-563, built 1963 (OpenAirDocs) - Reported make and model: CONTINENTAL COPTERS INC 47G - Registry model: [Continental Copters 47G](https://openairdocs.org/model/continental-copters-47g) (registry code 2390105) (OpenAirDocs) - Registry engine: [Franklin 6V4 series](https://openairdocs.org/engine/franklin-6v4-series) (registry code 27033, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: CCI-563 - Year built: 1963 - Airframe hours: 2851 - Engines: FRANKLIN 6V4 SERIES 210 horsepower reciprocating - Damage: Substantial damage - Flight: Positioning, Part 91 - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, June 26, 2013, 250 hours before - Departed: M97, Morehead, KY - Destination: Sandy Hook, KY ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 34; injuries: none; commercial, private; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 1, without waivers/limitations; last flight review July 31, 2012; seat: left; restraint: lap only; flight hours: 685 total, 91 in this make and model, 355 as pilot in command, 80 in the last 90 days, 51 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 7 statute miles - Lowest ceiling: 5,000 ft broken - Temperature: 77 °F, dew point 73 °F - Altimeter: 29.95 inHg - Observed at: IOB, 21 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 20130831018569A](https://openairdocs.org/incident/20130831018569A), Aug 31, 2013: Continental Copters Inc 47G, Sandy Hook, KY, Substantial damage. A bell 47G helicopter was operating near Sandy Hook KY. During the landing phase of the pilot lost use of tail rotor, pilot began auto rotation procedures.… ## Other investigations on N6356X (2) 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. - [NTSB SEA79FYM51](https://openairdocs.org/ntsb/SEA79FYM51), Jul 18, 1979: Bell 47G (N6356X), Embler, OR, substantial damage - [NTSB SEA78DYP35](https://openairdocs.org/ntsb/SEA78DYP35), Jun 23, 1978: Bell 47G (N6356X), Anatone, WA, substantial damage ## Docket (12 files) The files NTSB released with the investigation on September 26, 2013, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=87929. 6.3 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40400847&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Weather Data (item 2, .PDF, 123 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40400848&FileExtension=.PDF&FileName=Weather%20Data-Master.PDF - Correspondence with Pilot (item 3, .PDF, 81 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40400849&FileExtension=.PDF&FileName=Correspondence%20with%20Pilot-Redacted.PDF - FAA Inspector's Statement (item 4, .PDF, 39 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40400850&FileExtension=.PDF&FileName=FAA%20Inspector%27s%20Statement-Redacted.PDF - Diagram of Tail Rotor Drive (item 5, .PDF, 197 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40400851&FileExtension=.PDF&FileName=Diagram%20of%20Tail%20Rotor%20Drive-Master.PDF - Photo 1: Aft Section of Tail Boom, Damaged from Impact with Main Rotor Blade (FAA Digital Photo) (item 6, .PDF, 165 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40400852&FileExtension=.PDF&FileName=Photo%201%3A%20Aft%20Section%20of%20Tail%20Boom,%20Damaged%20from%20Impact%20with%20Main%20Rotor%20Blade%20(FAA%20Digital%20Photo)-Master.PDF - Photo 2: Aft Section of Tail Boom, Note Missing Section of Tail Rotor Drive Shaft (FAA Digital Photo) (item 7, .PDF, 1.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40400853&FileExtension=.PDF&FileName=Photo%202%3A%20Aft%20Section%20of%20Tail%20Boom,%20Note%20Missing%20Section%20of%20Tail%20Rotor%20Drive%20Shaft%20(FAA%20Digital%20Photo)-Master.PDF - Photo 3: Damage to Main Rotor Blade Leading Edge (FAA Digital Photo) (item 8, .PDF, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40400854&FileExtension=.PDF&FileName=Photo%203%3A%20Damage%20to%20Main%20Rotor%20Blade%20Leading%20Edge%20(FAA%20Digital%20Photo)-Master.PDF - Photo 4: Internal Gears of Tail Rotor Gear Box (Photo Provided by Pilot) (item 9, .PDF, 264 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40400856&FileExtension=.PDF&FileName=Photo%204%3A%20Internal%20Gears%20of%20Tail%20Rotor%20Gear%20Box%20(Photo%20Provided%20by%20Pilot)-Master.PDF - Photo 5: Internal Gears of Tail Rotor Gear Box (Photo Provided by Pilot) (item 10, .PDF, 276 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40400857&FileExtension=.PDF&FileName=Photo%205%3A%20Internal%20Gears%20of%20Tail%20Rotor%20Gear%20Box%20(Photo%20Provided%20by%20Pilot)-Master.PDF - Photo 6: Aft Extension Shaft Splines (Photo Provided by Pilot) (item 11, .PDF, 179 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40400859&FileExtension=.PDF&FileName=Photo%206%3A%20Aft%20Extension%20Shaft%20Splines%20(Photo%20Provided%20by%20Pilot)-Master.PDF - Photo 7: Interior of Extension Housing Tube and Extension Shaft, Note Scoring on Tube Surface (Photo Provided by Pilot) (item 12, .PDF, 301 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40400860&FileExtension=.PDF&FileName=Photo%207%3A%20Interior%20of%20Extension%20Housing%20Tube%20and%20Extension%20Shaft,%20Note%20Scoring%20on%20Tube%20Surface%20(Photo%20Provided%20by%20Pilot)-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.