# NTSB NYC96GA083: Bell 206L-1, N79SP, Charleston, WV, April 4, 1996 - Type: NTSB accident investigation - Classification: Accident · Fatal · Final report - Date: April 4, 1996, 10:19 local (15:19 UTC) - Place: Charleston, WV - Coordinates: 38.310569, -81.750114 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=38.3106&lon=-81.7501&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 2 fatal - Status: Completed, report May 2, 1997 - Report: Approved by Office Director - Safety recommendations: Yes - NTSB case key (mKey): 39099 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=NYC96GA083 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/39099/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=39099 - Page: https://openairdocs.org/ntsb/NYC96GA083 ## Probable cause the helicopter manufacturer's inadequate maintenance service bulletin inspection interval which failed to provide timely detection of preexisting fatigue cracks in the tail boom. Factors were: the manufacturer's failure to develop a modification of the failed area, and the failure of the FAA certification office to monitor and act upon the significant number of reports of tail boom cracking that were reported by industry. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, cruise - misc rotorcraft,tail boom - fatigue (cause) - maintenance,service bulletin/letter - inadequate, manufacturer (cause) - acft/equip,inadequate design, manufacturer (contributing factor) - inadequate substantiation process,insuff review, faa(organization) (contributing factor) - misc rotorcraft,tail boom - separation - In flight collision with object, descent - uncontrolled ## Analysis Three minutes after takeoff, an ATC controller heard a garbled transmission with an ELT signal in the background. Witnesses observed the helicopter in level flight, about 300 feet above a hill, when a tail section separated from the helicopter, followed by the helicopter entering a spin, rolling inverted, and descending into trees. The tail boom section aft of boom station 167, which included the upper and lower vertical fin, the tail rotor gear box, and the tail rotor hub and blades, was found 650 feet from the main wreckage. Examination revealed fatigue cracks at the separated area of the tail section. Due to reports of tail boom cracking, an Alert Service Bulletin had been published by the manufacturer in 1987 recommending an inspection of the tail boom every 100 hours, which had been complied with by the operator. The manufacturer and the FAA certification office were aware of a few reports of tail boom cracking, and were not aware of over 220 Service Difficulty Reports that concerned cracks in the Bell 206L tail booms. A doubler was added to the failed area on recent production models; however, no modifications were developed to add a doubler to the failed area of the older models. ## Factual narrative HISTORY OF FLIGHT On April 4, 1996, at 1019 eastern standard time, a Bell 206L-1, a helicopter, N79SP, owned and operated by the West Virginia State Police, was destroyed during an in-flight break-up and collision with terrain, 2.5 miles west of the Yeager Airport, Charleston, West Virginia. The commercial pilot and passenger were fatally injured. Visual meteorological conditions prevailed for the positioning flight that originated at the Yeager Airport (CRW), at 1016. No flight plan had been filed for the flight conducted under 14 CFR Part 91. The State Police pilot and passenger departed the State Police Academy where the helicopter was based, and flew a 1.5 hour flight. The helicopter was landed at CRW, refueled, and departed in a westerly direction for the return flight to the academy. About 1019, a garbled transmission with an ELT signal in the background was received by a CRW Air Traffic Controller. When the controller attempted contact with N79SP, there was no response. Forty-four witnesses observed the helicopter during various segments of the accident sequence, and many observed the helicopter in level flight about 300 feet above a hill before the event began. Twenty-one witnesses stated that they observed something depart from the tail of the helicopter, followed by the helicopter entering a spin, rolling inverted, and descending into trees. Two of the witnesses stated that they observed the helicopter collide with birds. One of these witnesses stated, "...I did not see anything fall off or break off of the aircraft other than the bird which fell off to the right..." A third witness stated, "...I saw a big dark piece of something, that I originally thought might have been a bird, come off of the helicopter. The piece then seemed to move back into the rotor on top and the helicopter started going down..." Another witness stated: "...I saw something fly off ...it looked like it flew up into the propeller because it then ricocheted away from the helicopter...There were papers from it that blew over by where I was working. The wind blew them there eventually. It seemed to be flying normal to the point that something flew off of it. It was flying slow. I didn't notice any birds flying around it..." Fourteen other witnesses described their observations: "...I didn't notice anything unusual about the sound of the helicopter or the way it was flying that day until it got to the top of the hill...then I saw part of the rear tail section fall off and then the helicopter went into a left bank and did a complete 360 degree;...something black and square looking fell off the side of the helicopter;...I observed a piece of the aircraft fly off;...Something fell behind the helicopter that made a noise when it broke and hit the tail;...I saw one of the main blades come off and shoot straight out. The helicopter turned again and the rotor came off;...the tail end blew off and it was like it went off the back and then dropped straight down. The helicopter then made a 360 degree rotation;...I saw the top propeller fly off;...I saw something fly off the helicopter. It looked like it came form the middle, then I saw something come from the back. It looked like a piece of metal;...I noticed something fall off the rear. At this time the helicopter was still going forward but was wobbling;...I noticed something black about the size of a basketball fall off the helicopter;...I saw something falling from the rear of the helicopter. It looked to be pretty good size;...I looked up and [saw] the tail fin drop off;...As he was going down, papers were flying out of it;...When we first saw it, it drew our attention and nothing appeared to be out of the ordinary. He dropped down a little bit, and tried to pull himself back up, then it looked like his tail end fell off. He started to twirl then went straight down..." The helicopter struck the ground inverted, and a post crash fire erupted. The accident occurred during the hours of daylight at approximately 38 degrees, 23 minutes north latitude, and 81 degrees, 39 minutes west longitude. PERSONNEL INFORMATION The pilot, Mr. Charles M. Turner, held a Commercial Pilot Certificate with an instrument rating for rotorcraft-helicopter, and a Private Pilot Certificate for airplane single engine land. His most recent Federal Aviation Administration (FAA) Second Class Medical Certificate was issued on February 29, 1996. A review of Mr. Turner's pilot log book revealed that he had logged approximately 4,535 hours of total flying experience, of which about 4,400 hours were in helicopters, and 2,500 hours were in this make and model WRECKAGE AND IMPACT INFORMATION The helicopter wreckage was examined at the accident site on April 4 and 5, 1996. It was then removed to a hangar and examined further. The examination revealed that all major components of the helicopter were accounted for; however, several components were separated from the main fuselage and located up to 1,400 feet to the east. The main fuselage was inverted on the east slope of a ravine, at an approximate elevation of 820 feet above mean sea level (msl). The height of the highest terrain in the area was over 1,020 feet msl, and the bottom of the ravine was about 740 feet msl. Debris located about 1,400 feet east of the fuselage included; shredded papers from the cockpit; blue paint chips and sheet metal that were matched to the nose battery compartment area of the fuselage; sections of brown plastic that were matched to the cockpit overhead circuit breaker panel; and a 6 inch long black and yellow paint chip that was matched to a position on the (red) main rotor blade, 3 feet from the hub end of the blade. The tail boom section, aft of center of gravity (CG) station 362 (boom station 167), was located about 650 feet east of the main fuselage. This included the upper and lower vertical fin, the tail rotor gear box, and the tail rotor hub and blades. The tail section at station 362 was torn and twisted, and no external impact marks were visible on the sheet metal. Both tail rotor blades were bent chord wise. The bend in the white blade was 4 inches from the hub and displayed aft compression wrinkles at the bend. The bend in the red blade was 2 inches from the hub. The white blade had an indentation 1/2 inch deep in the leading edge, about 4 inches from the end of the blade. The white blade also displayed several chord wise scratches at the leading edge, similar to the rivet pattern on the right side of the tail boom. The tail rotor output shaft turned freely, and continuity was observed to the input shaft when the tail rotor was turned. The splines inside of the input shaft were intact and not damaged. Rotational scratches and scoring were observed on the inside of the tail rotor drive shaft cover. The upper and lower vertical fins were intact. The upper vertical fin had a 1/2 inch indentation on its leading edge, about 5 inches from the top of the fin. The main rotor hub and blades were separated from the main transmission mast. The hub and the attached sections of main rotor blades were located about 100 feet southeast, up slope, from the main wreckage. The mast separation displayed torsional overload, and had separated at the yoke dynamic stop. The leading edges of both main rotor blades remained attached to the rotor hub; however, several sections of both blades were separated and located up to 400 feet from the hub. One section of the (red) main rotor blade was found 300 feet east of the main fuselage. On the ground next to this section of blade was a piece of the battery cover, with an indentation similar to the leading edge of the main rotor blades. The collective sleeve and swashplate were separated from the transmission mast and located about 25 feet northeast of the main fusela ## Aircraft - Registration: [N79SP](https://openairdocs.org/deregistered/N79SP-1997-03-25), registration cancelled 1997-03-25, S/N 45540 (OpenAirDocs) - Reported make and model: Bell 206L-1 - Registry model: [Bell Helicopter Textron 206L-1](https://openairdocs.org/model/bell-helicopter-textron-206l-1) (registry code 1182107) (OpenAirDocs) - Category: Helicopter - Serial number: 45540 - Airframe hours: 2898 - Engines: Allison 250-C30P 650 horsepower turbo shaft - Damage: Destroyed - Fire: On-Ground - Flight: Public aircraft, Part 91 - Registered owner: West Virginia State Police - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, November 10, 1996, 108 hours before - Departed: CRW, WV - Destination: WV07, S. CHARLESTON, WV - Airport: CRW, Yeager ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 41; commercial; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 2, valid medical--no waivers/lim.; seat: right; toxicology performed; flight hours: 4,537 total, 2,500 in this make and model, 4,031 as pilot in command, 55 in the last 90 days, 27 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 230° at 11 knots, gusting 21 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 79 °F, dew point 34 °F - Altimeter: 29.00 inHg - Observed at: CRW, 3 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 19960404045829A](https://openairdocs.org/incident/19960404045829A), Apr 4, 1996: Bell 206L1, Charleston, WV, Destroyed, 2 fatal. Tail boom skin seperated due fatigue in flight. Lost tail section. 206 then broke up. Tail skin inspection overdue. ## Docket (35 files) The files NTSB released with the investigation on November 19, 1996, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=39099. 10.0 MB in all. - Supplement C (item 1, .PDF, 346 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058215&FileExtension=.PDF&FileName=Supplement%20C-Master.PDF - Supplement D (item 2, .PDF, 426 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058216&FileExtension=.PDF&FileName=Supplement%20D-Master.PDF - Supplement K (item 3, .PDF, 343 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058217&FileExtension=.PDF&FileName=Supplement%20K-Master.PDF - Supplement G (item 4, .PDF, 88 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058218&FileExtension=.PDF&FileName=Supplement%20G-Master.PDF - Supplement S (item 5, .PDF, 55 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058219&FileExtension=.PDF&FileName=Supplement%20S-Master.PDF - Witness Statements and Interview Summaries (item 6, .PDF, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408310&FileExtension=.PDF&FileName=Witness%20Statements%20and%20Interview%20Summaries-Redacted.PDF - Crash Maps and Diagrams (item 7, .PDF, 562 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058221&FileExtension=.PDF&FileName=Crash%20Maps%20and%20Diagrams-Master.PDF - FAA Airworthiness Directive (item 8, .PDF, 233 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408285&FileExtension=.PDF&FileName=FAA%20Airworthiness%20Directive-Redacted.PDF - Police Report (item 9, .PDF, 238 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408295&FileExtension=.PDF&FileName=Police%20Report-Redacted.PDF - ATC Statements and Transcript of Radio Communications (item 10, .PDF, 307 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408297&FileExtension=.PDF&FileName=ATC%20Statements%20and%20Transcript%20of%20Radio%20Communications-Redacted.PDF - N79SP Flight Log and Fueling Record (item 11, .PDF, 398 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058225&FileExtension=.PDF&FileName=N79SP%20Flight%20Log%20and%20Fueling%20Record-Master.PDF - N79SP 100 Hour Work Order, November 1995 to February 1996 (item 12, .PDF, 309 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408298&FileExtension=.PDF&FileName=N79SP%20100%20Hour%20Work%20Order,%20November%201995%20to%20February%201996-Redacted.PDF - BHT Letter to FAA Recommending AD (item 13, .PDF, 42 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408299&FileExtension=.PDF&FileName=BHT%20Letter%20to%20FAA%20Recommending%20AD-Redacted.PDF - Bell Helicopter Textron Laboratory Report of Tail Boom (item 14, .PDF, 227 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058228&FileExtension=.PDF&FileName=Bell%20Helicopter%20Textron%20Laboratory%20Report%20of%20Tail%20Boom-Master.PDF - BHT 206L-4 Doubler Modification (item 15, .PDF, 78 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408300&FileExtension=.PDF&FileName=BHT%20206L-4%20Doubler%20Modification-Redacted.PDF - Bell Helicopter Textron Hydraulic Servo Test Report (item 16, .PDF, 100 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408301&FileExtension=.PDF&FileName=Bell%20Helicopter%20Textron%20Hydraulic%20Servo%20Test%20Report-Redacted.PDF - Statement of Party Representatives to NTSB Investigation (item 17, .PDF, 287 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408302&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - BHT Alert Service Bulletin 206L-87-47 (item 18, .PDF, 647 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058232&FileExtension=.PDF&FileName=BHT%20Alert%20Service%20Bulletin%20206L-87-47-Master.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 19, .PDF, 76 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408304&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF - BHT Cracking Reports (item 20, .PDF, 82 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058234&FileExtension=.PDF&FileName=BHT%20Cracking%20Reports-Master.PDF - Toxicological Reports (item 21, .PDF, 130 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058235&FileExtension=.PDF&FileName=Toxicological%20Reports-Master.PDF - Service Difficulty Reports (item 22, .PDF, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408306&FileExtension=.PDF&FileName=Service%20Difficulty%20Reports-Redacted.PDF - N79SP Weight and Balance Computations (item 23, .PDF, 249 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058237&FileExtension=.PDF&FileName=N79SP%20Weight%20and%20Balance%20Computations-Master.PDF - NTSB Safety Recommendation (item 24, .PDF, 224 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408307&FileExtension=.PDF&FileName=NTSB%20Safety%20Recommendation-Redacted.PDF - Photograph #1 View of wreckage as found, looking southeast. (item 25, .PDF, 20 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058239&FileExtension=.PDF&FileName=Photograph%20%231%20View%20of%20wreckage%20as%20found,%20looking%20southeast.-Master.PDF - Photograph #3 View of tail boom as found. Arrow #1 main fuselage. Arrow #2 twist in tail boom. (item 26, .PDF, 19 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058240&FileExtension=.PDF&FileName=Photograph%20%233%20View%20of%20tail%20boom%20as%20found.%20%20Arrow%20%231%20main%20fuselage.%20%20Arrow%20%232%20twist%20in%20tail%20boom.-Master.PDF - Photograph #2 View of wreckage as found, looking southeast. (item 27, .PDF, 19 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058241&FileExtension=.PDF&FileName=Photograph%20%232%20View%20of%20wreckage%20as%20found,%20looking%20southeast.-Master.PDF - Photograph #4 Tail boom separation near CG station 362, as found. (item 28, .PDF, 20 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058242&FileExtension=.PDF&FileName=Photograph%20%234%20Tail%20boom%20separation%20near%20CG%20station%20362,%20as%20found.-Master.PDF - Photograph #5 View of separated tail section, as found. (item 29, .PDF, 20 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058243&FileExtension=.PDF&FileName=Photograph%20%235%20View%20of%20separated%20tail%20section,%20as%20found.-Master.PDF - Photograph #6 Separated tail section. (item 30, .PDF, 20 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058244&FileExtension=.PDF&FileName=Photograph%20%236%20Separated%20tail%20section.-Master.PDF - Photograph #7 Tail rotor blade (red). (item 31, .PDF, 19 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058245&FileExtension=.PDF&FileName=Photograph%20%237%20Tail%20rotor%20blade%20(red).-Master.PDF - Photograph #8 Tail rotor blade (white), arrow #1 displays compression wrinkles, arrow #2 indentation. (item 32, .PDF, 16 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058246&FileExtension=.PDF&FileName=Photograph%20%238%20Tail%20rotor%20blade%20(white),%20arrow%20%231%20displays%20compression%20wrinkles,%20arrow%20%232%20indentation.-Master.PDF - Photograph #9 Main rotor hub and blades, as found. (item 33, .PDF, 20 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058247&FileExtension=.PDF&FileName=Photograph%20%239%20Main%20rotor%20hub%20and%20blades,%20as%20found.-Master.PDF - Photograph #10 Paint chip found on hill, 1,400 feet from main rotor blade. (item 34, .PDF, 9 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40058248&FileExtension=.PDF&FileName=Photograph%20%2310%20Paint%20chip%20found%20on%20hill,%201,400%20feet%20from%20main%20rotor%20blade.-Master.PDF - NTSB Metallurgist's Factual Repot (Original photos contained in report are on file) (item 35, .PDF, 726 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408309&FileExtension=.PDF&FileName=NTSB%20Metallurgist%27s%20Factual%20Repot%20(Original%20photos%20contained%20in%20report%20are%20on%20file)-Redacted.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.