# NTSB IAD98FA005: Bell 206B, N911RH, Sago, WV, October 12, 1997 - Type: NTSB accident investigation - Classification: Accident · Fatal · Field investigation · Final report - Date: October 12, 1997, 11:13 local (15:13 UTC) - Place: Sago, WV - Coordinates: 38.980693, -80.220832 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=38.9807&lon=-80.2208&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 4 fatal - Status: Completed, report July 23, 1999 - Report: Approved by Office Director - NTSB case key (mKey): 28241 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=IAD98FA005 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/28241/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=28241 - Page: https://openairdocs.org/ntsb/IAD98FA005 ## Probable cause The improper overhaul of the turbine governor by the manufacturer, which resulted in the loss of power. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power, maneuvering - turboshaft engine,free turbine governor - failure (cause) - maintenance,overhaul - improper, manufacturer (cause) - Forced landing, descent - emergency - terrain condition - none suitable - In flight collision with object, emergency descent/landing - object - tree(s) ## Analysis A helicopter was transporting passengers to a remote site when it dropped in a flat attitude and impacted into trees. A witness said he watched as the helicopter approached and circled the local area. As the helicopter flew overhead for the second time, he waved his arms to attract the pilot's attention. As the helicopter continued past him again, he thought that they were taking aerial photographs of the site. He said that the helicopter appeared to be lower and slower on its second pass overhead. Examination of the engine revealed uncommanded engine shut downs. During bench testing, the power turbine governor failed to limit fuel flow, and during disassembly it was revealed that a machine self locking hex nut had backed off the muscles valve stem. Examination of the muscles valve components revealed that the threaded valve stem was below the minimum requirements for a UNJ thread, and the flank angle was too large. The turbine governor, with zero Time Since Overhaul, was installed on the engine in January 1997. The governor was last overhauled at the manufacturer's facility during May-June 1996. ## Factual narrative HISTORY OF FLIGHT On October 12, 1997, about 1113 eastern daylight time, a Bell 206B, N911RH, was destroyed as it impacted the terrain in a wooded area near Sago, West Virginia. The certificated commercial pilot and three passengers received fatal injuries. The helicopter was owned and operated by Royale Helicopter Services, Incorporated, Burgettstown, Pennsylvania. Visual meteorological conditions prevailed and no flight plan was filed for the flight conducted under 14 CFR Part 135. According to a Anker Coal Group, Inc. employee, Royale Helicopter Services was hired to fly to coal production sites to obtain photographs for a new brochure. The helicopter departed Burgettstown, Pennsylvania, and flew to Morgantown Municipal Airport, Morgantown, West Virginia, where the President of Anker Coal Group, Inc., his wife, and a photographer boarded the helicopter. The helicopter picked up another company employee at his residence, and then, flew to the first site. Upon landing, everyone, except the pilot, exited the helicopter while the photographer took pictures for approximately 1 hour. One company employee did not re-board the helicopter, but drove a vehicle to the next location. The employee stated that at the new site, he watched as the helicopter approached and circled the local area. As the helicopter flew overhead for the second time, he waved his arms to attract the pilot's attention. As the helicopter continued past him again, he thought that they were taking aerial photographs of the site. The employee stated that the helicopter appeared to be lower and slower on its second pass overhead. The helicopter, approximately a quarter mile away, appeared to be making a left turn when it dropped in a flat attitude into the trees. The employee stated that he saw the tree limbs shaking, but was not certain that it impacted the trees. He quickly drove to the nearest telephone and called the local authorities. The accident occurred during the hours of daylight approximately 38 degrees, 54 minutes north latitude, and 80 degrees, 12 minutes west longitude. PERSONNEL INFORMATION The pilot held a commercial pilot certificate with ratings for airplane single and multiengine land, rotorcraft helicopter, and instrument airplane and helicopter. He also held a flight instructor certificate for rotorcraft-helicopter. The pilot held a mechanic certificate with ratings for airframe and powerplant. His most recent Federal Aviation Administration (FAA) Second Class Medical Certificate was issued on February 10, 1997. The pilot was the President, Chief Pilot, and Maintenance Officer of Royale Helicopter Services. He attended the Bell Helicopter customer training academy offsite location at Helicopter Aviation Services (HAS), Mount Pleasant, Pennsylvania, on October 23, 1996. On his pilot's registration form, he wrote that he possessed 15,000+ hours of flight time, with 9,000+ hours of total time in this model. The check pilot for the course wrote in the remarks section, "Completed 206B Recurrent Training. Good pilot-Safe in all maneuvers." AIRCRAFT INFORMATION The helicopter was a Bell 206B with an Allison 250-C20 engine. The last annual/100 hour inspection was completed on October 9, 1997. On the date of the inspection, the airframe had a total time of 5,970.6 hours, and the engine had a total time of 5,927.9 hours. WRECKAGE AND IMPACT INFORMATION The wreckage was examined at the accident site on October 13, 1997. The examination revealed that all major components of the helicopter were accounted for at the scene, and that the helicopter came to rest on its left side, on an approximate magnetic heading of 280 degrees, at a ground elevation of about 1,760 feet above mean sea level (MSL). The wreckage was located in a wooded area on a hill with a down slope of about 30 degrees. The nose of the helicopter was crushed inward, with all the Plexi-glas broken out. The landing skids were separated from the fuselage, and the fuel tank was ruptured with the surrounding soil soaked with fuel. The tail boom was bent downward, the tail rotor drive shaft was intact, with minimal damage to the tail rotor. One blade of the tail rotor was bent and the other blade was straight and stuck in the ground. The pitch change tube was fractured near the bend in the tail boom, but exhibited continuity to the tail rotor. Minimal damage was found to the leading edge of both the main and tail rotor blades, with score marks found on the underside of one main rotor blade. The engine remained intact exhibiting minimal damage, with the engine compartment found very clean and no signs of fuel or oil leakage. The fuel control throttle position was found near flight idle, and the throttle linkage was jammed at that position. The fuel shut off switch was found in the "on" position, and confirmed by sighting of the valve in the open position. Flight control continuity for the collective, cyclic, and anti-torque was confirmed. Fractures of the collective, cyclic, and anti-torque tubes, similar to overload, were found at the bottom of the control tunnel (broom closet). A small bag, containing a 5/64 inch Allen wrench, a copy of page 3-160 and 3-161 of the 250-C20 Series Operation and Maintenance Manual, a set of duck bill pliers, and a hemostat clamp, was found in the baggage compartment. On October 14, 1997, the wreckage was removed from the wooded area and taken to a hangar. The engine's gas producer and power turbine drive trains exhibited continuity, and rotated freely. The linear actuator was fractured at the forward clevis attachment point. A Chandler Evans (CECO) fuel system was on the engine. The fuel filter was clean, contained fuel, and the by-pass button was not popped. All fuel, air, and oil lines were tight, and no leaks detected. The main rotor drive shaft and the tail rotor segmented drive shaft exhibited minimal indications of rotation at impact. The engine was removed from the wreckage and transported to a test facility. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the pilot, on October 14, 1997, by James L. Frost, M.D., Deputy Chief Medical Examiner, State of West Virginia, South Charleston, West Virginia. The toxicological testing report revealed negative for drugs and alcohol. TEST AND RESEARCH The engine was received at Airwork Corporation, Millville, New Jersey and found in acceptable condition for operational testing. On November 4, 1997, the engine was started, accelerated, and stabilized at 100% N2. A dynometer load was applied and at 91% N1, an uncommanded engine shut down occurred. The uncommanded engine shut down repeated itself on subsequent tests at the same power setting/parameters. After telephone discussions with representatives from CECO, the power turbine governor unit and the fuel control were removed from the engine and taken to West Hartford, Connecticut, on November 5, 1997. On November 6, 1997, both the power turbine governor unit and the fuel control were bench tested "as received" at CECO. The power turbine governor was found to "allow the same quantity of fuel flow entering the governor to be discharged by the governor" and the fuel control was slightly above service limits. A systematic plan was organized to disassemble the governor. The disassembly began with the inspections of the mechanical linkage (lever assembly), speed sensor assembly and fixed orifice, and the main diaphragm assemblies. No anomalies were found. Inspection of the muscles valve assembly, which consisted of a diaphragm, diaphragm cup, threaded valve and a self-locking hex nut, revealed that the hex nut, P/N 94289, had backed off the threaded valve stem, with less than one turn of thread engagement remaining. The valve assembly was removed from the governor and taken to a binocular microscope for photos. After photos were taken, the nut fell off the threaded valve ste ## Aircraft - Registration: [N911RH](https://openairdocs.org/deregistered/N911RH-2017-05-23), registration cancelled 2017-05-23, S/N 1583, built 1975 (OpenAirDocs) - Reported make and model: Bell 206B - Registry model: [Bell 206B](https://openairdocs.org/model/bell-206b) (registry code 1181511) (OpenAirDocs) - Registry engine: [Allison 250 SER 400HP](https://openairdocs.org/engine/allison-250-ser-400hp) (registry code 03013, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 1583 - Airframe hours: 5971 - Engines: Allison 250-C20B 400 horsepower turbo shaft - Damage: Destroyed - Flight: Part 135 - Registered owner: Royale Helicopter Service, Inc - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, October 9, 1997, 3 hours before - Departed: NONE, SPRUCE FORK, WV - Destination: NONE, SAWMILL RUN, WV ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 54; commercial, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane, helicopter; medical: class 2, valid medical--w/ waivers/lim; seat: right; toxicology performed; flight hours: 14,000 total, 9,200 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 55 °F, dew point 52 °F - Altimeter: 30.00 inHg - Observed at: EKN, 16 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 19971012030609A](https://openairdocs.org/incident/19971012030609A), Oct 12, 1997: Bell 206B, Sago, WV, Destroyed, 4 fatal. Bell 206B crashed in wooded area all 4 POB suffered fatal inj, acft was destroyed, Sago, WV (.4) a helicopter was transporting passengers to a remote site when… ## Docket (22 files) The files NTSB released with the investigation on June 17, 1999, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=28241. 9.0 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40440778&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Supplement C (item 2, .PDF, 409 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40106821&FileExtension=.PDF&FileName=Supplement%20C-Master.PDF - Supplement D (item 3, .PDF, 539 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40106822&FileExtension=.PDF&FileName=Supplement%20D-Master.PDF - Supplement S (item 4, .PDF, 84 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40106823&FileExtension=.PDF&FileName=Supplement%20S-Master.PDF - Materials Laboratory Factual Report (item 5, .PDF, 501 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40440779&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report-Redacted.PDF - Witness Statements (item 6, .PDF, 192 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40440780&FileExtension=.PDF&FileName=Witness%20Statements-Redacted.PDF - Airwork Inspection Package (item 7, .PDF, 919 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40440781&FileExtension=.PDF&FileName=Airwork%20Inspection%20Package-Redacted.PDF - Chandler Evans Model MC-40 Fuel Control/Power Turbine Governor Investigation (item 8, .PDF, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40440782&FileExtension=.PDF&FileName=Chandler%20Evans%20Model%20MC-40%20Fuel%20Control%2FPower%20Turbine%20Governor%20Investigation-Redacted.PDF - Rolls-Royce Engine and Fuel System Investigation (item 9, .PDF, 966 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40440783&FileExtension=.PDF&FileName=Rolls-Royce%20Engine%20and%20Fuel%20System%20Investigation-Redacted.PDF - Bell Helicopter Pilot Registration Form and notes found at accident site (item 10, .PDF, 306 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40440784&FileExtension=.PDF&FileName=Bell%20Helicopter%20Pilot%20Registration%20Form%20and%20notes%20found%20at%20accident%20site-Redacted.PDF - Chandler Evans Overhaul Report and Sales Order for the Power Turbine Governor (item 11, .PDF, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40440785&FileExtension=.PDF&FileName=Chandler%20Evans%20Overhaul%20Report%20and%20Sales%20Order%20for%20the%20Power%20Turbine%20Governor-Redacted.PDF - 250-C20 Series Engine Fuel System Trouble Shooting guide (item 12, .PDF, 362 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40440786&FileExtension=.PDF&FileName=250-C20%20Series%20Engine%20Fuel%20System%20Trouble%20Shooting%20guide-Redacted.PDF - Statement of Party Representatives to NTSB Investigation (item 13, .PDF, 133 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40440787&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 14, .PDF, 112 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40440788&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF - Statement of Record (item 15, .PDF, 8 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40106835&FileExtension=.PDF&FileName=Statement%20of%20Record-Master.PDF - CECO Approval for Report Use (item 16, .PDF, 10 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40106836&FileExtension=.PDF&FileName=CECO%20Approval%20for%20Report%20Use-Master.PDF - Photo #1 Top left view of Helicopter on left side and cockpit area wedged between trees. (item 17, .PDF, 37 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40106815&FileExtension=.PDF&FileName=Photo%20%231%20Top%20left%20view%20of%20Helicopter%20on%20left%20side%20and%20cockpit%20area%20wedged%20between%20trees.-Master.PDF - Photo #2 Top view with tail boom bent out of view-minimum damage to top of fuselage and rotor blade. (item 18, .PDF, 39 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40106816&FileExtension=.PDF&FileName=Photo%20%232%20Top%20view%20with%20tail%20boom%20bent%20out%20of%20view-minimum%20damage%20to%20top%20of%20fuselage%20and%20rotor%20blade.-Master.PDF - Photo #3 View of main rotor blade with scratching and minimum damage to leading edge (top). (item 19, .PDF, 44 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40106817&FileExtension=.PDF&FileName=Photo%20%233%20View%20of%20main%20rotor%20blade%20with%20scratching%20and%20minimum%20damage%20to%20leading%20edge%20(top).-Master.PDF - Photo #4 Bottom view of Helicopter as it was found. Note bottom of fuselage where fuel tank. (item 20, .PDF, 33 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40106818&FileExtension=.PDF&FileName=Photo%20%234%20Bottom%20view%20of%20Helicopter%20as%20it%20was%20found.%20%20Note%20bottom%20of%20fuselage%20where%20fuel%20tank.-Master.PDF - Photo #5 Cockpit area of Helicopter during removal from wooded area. Note: Tree cut to help with extraction and wreckage being hoisted by crane at mast area. (item 21, .PDF, 47 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40106819&FileExtension=.PDF&FileName=Photo%20%235%20Cockpit%20area%20of%20Helicopter%20during%20removal%20from%20wooded%20area.%20%20Note%3A%20%20Tree%20cut%20to%20help%20with%20extraction%20and%20wreckage%20being%20hoisted%20by%20crane%20at%20mast%20area.-Master.PDF - Photo #6 Right side of wreckage being hoisted to flat bed truck. Note condition of engine compartment on top. (item 22, .PDF, 41 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40106820&FileExtension=.PDF&FileName=Photo%20%236%20Right%20side%20of%20wreckage%20being%20hoisted%20to%20flat%20bed%20truck.%20%20Note%20condition%20of%20engine%20compartment%20on%20top.-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.