# NTSB FTW99FA192: MBB BK-117-B2, N110HH, Fresno, TX, July 17, 1999 - Type: NTSB accident investigation - Classification: Accident · Fatal · Field investigation · Final report - Date: July 17, 1999, 12:31 local (17:31 UTC) - Place: Fresno, TX - Coordinates: 29.530714, -95.449653 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=29.5307&lon=-95.4497&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 3 fatal - Status: Completed, report May 9, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 46849 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW99FA192 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/46849/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=46849 - Page: https://openairdocs.org/ntsb/FTW99FA192 ## Probable cause the loss of control during approach due to the corrosion of the T-T strap which resulted in fatigue cracking and subsequent separation of the strap and main rotor blade from the helicopter. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Rotor failure/malfunction, approach - vfr pattern - base leg/base to final - rotor system,main rotor tension torsion bar - corroded (cause) - rotor system,main rotor tension torsion bar - fatigue (cause) - rotor system,main rotor tension torsion bar - separation (cause) - Loss of control - in flight, approach - vfr pattern - base leg/base to final - aircraft control - not possible, pilot in command - In flight collision with terrain/water, descent - uncontrolled - terrain condition - ground ## Analysis The helicopter was making a VFR approach to a fueling site when witnesses observed components of the main rotor system separate from the helicopter. Subsequently, the helicopter entered an uncontrollable descent and impacted the ground. Examination of the helicopter revealed that one of the four main rotor blades separated due to the failure of the tension-torsion strap (T-T strap), which secured the blade to the main rotor head. Examination of the failed T-T strap revealed that the polyurethane protective coating had debonded from a portion of the strap allowing corrosive agents, including carbon, sulphur, and chlorine into the strap. The strap separated as a result of fatigue cracking of the wires making up the strap. The fatigue cracking emanated from corrosion pits and deposits that were introduced to the strap when the polyurethane protective coating debonded. The T-T strap had accumulated a total of 7,815.3 flight hours and 35,971 flights at the time that it failed. It had been in service since the helicopter was manufactured in 1987. Following the accident, a life limit of 120 months or 25,000 flights (whichever comes first) was established for the T-T straps. ## Factual narrative HISTORY OF FLIGHT On July 17, 1999, at 1231 central daylight time, a Messerschmit-Bolkow-Blohm BK-117-B2 helicopter, N110HH, operating as LIFEFLIGHT 1, was destroyed when it impacted terrain following the separation of a main rotor blade during an approach to an unmanned fueling site near Fresno, Texas. The airline transport rated pilot and two medical crewmembers were fatally injured. The helicopter was registered to and operated by Hermann Memorial Hospital Systems, of Houston, Texas. Visual meteorological conditions prevailed for the 14 Code of Federal Regulations Part 91 positioning flight, for which a company VFR flight plan was filed. According to Hermann Hospital dispatch records, LIFEFLIGHT 1 departed Hermann Memorial Hospital at 1226 and was destined for the Columbia Clearlake Regional Hospital, near Clear Lake, Texas, with an intermediate refueling stop at the Fresno fueling site. At 1227, LIFEFLIGHT 1 was issued a clearance from Houston Hobby air traffic control tower into Hobby Class B airspace. At 1231, LIFEFLIGHT 1 reported that the landing area was in sight. No further communication was received from the helicopter. According to a witness, who was driving westbound on FM2234, he first noticed the LIFEFLIGHT helicopter flying southbound approximately level with powerlines. He stated that the helicopter turned to the left and hovered for a second, and then he observed "sparks or possible flames shoot out from the top middle of the helicopter," near the main rotor system. He witnessed pieces of the main rotor system separate from the helicopter. Subsequently, the helicopter entered a nose low attitude and passed behind trees out of the witness' view. Another witness, who was driving northbound on FM521, observed the LIFEFIGHT helicopter traveling southbound, approximately 35 feet agl. He stated that the helicopter made a left turn, as if it was going to land; he then observed an "explosion," and the helicopter impacted the ground. PERSONNEL INFORMATION The pilot was hired by Hermann Hospital on July 23, 1990. On July 27, 1990, he completed initial BK-117 ground and flight training, which was administered by American Eurocopter, Grand Prarie, Texas. On August 2, 1998, the pilot satisfactorily completed his most recent annual recurrent ground and flight training for the BK-117. On August 13, 1998, the FAA issued the pilot an airline transport certificate for helicopters. He also held a commercial certificate with airplane single and multi-engine land ratings and type ratings in the Bell 206 helicopter, Hughes 369 helicopter, and the Boeing Vertol 234. According to Pilot Flight Duty Time Forms that were provided by Hermann Hospital, the pilot had accumulated a total of 1,459.5 flight hours with Hermann Hospital, since his date of hire. There were no restrictions or limitations listed on the pilot's FAA second class medical certificate issued on June 7, 1999. The Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2), which was completed by Hermann Hospital, indicated that the pilot had accumulated a total of 9,233 flight hours, of which 8,763 hours were in rotorcraft. The two medical crewmembers, a flight nurse and a paramedic, were based at the Hermann Memorial Hospital. AIRCRAFT INFORMATION The 1987, red and black, twin-engine helicopter was equipped with two Honeywell LTS101-750B-1 turboshaft engines, a four bladed main rotor system, and a two bladed tail rotor. The airframe had accumulated a total of 7,815.3 flight hours and 35,971 flights at the time of the accident. The helicopter underwent its most recent inspection, in accordance with its approved inspection program, on July 7, 1999. The left engine had accumulated a total of 6,216.2 hours at the time of the accident and underwent its last 1,200-hour inspection on July 8, 1998. The right engine had accumulated a total of 2,737.4 hours at the time of the accident and underwent its most recent 1,200-hour inspection on October 6, 1998. The main rotor head and tension torsion straps (T-T straps) had accumulated a total of 7,815.3 hours at the time of the accident. The T-T straps had not been replaced since they were installed on the helicopter in 1987. The main rotor head and T-T straps were last inspected on May 1, 1997, in accordance with the manufacturer's recommended 2,400-hour inspection interval, at a total time of 6,027.1 hours. At the time of the accident, the T-T straps were not time-life-limited. The T-T straps installed on LIFEFLIGHT 1 were manufactured by Bendix Corporation. A T-T strap contains between 11,900 and 12,000 windings of grade 304 stainless steel wire continously wrapped around two steel bushings that are separated by a distance of approximately 9.6 inches. Each bushing contains an axial tube portion and a radial flange at the end of the tube portion. The area between the straight portions of the bundles of wires, between the bushings, is hollow. A cast polyurethane bushing retention block is installed adjacent to each bushing in the area between the straight portions of the bundle of wires. The wound wires, bushings, and bushing retention blocks are encapsulated in polyurethane, to prevent exposure of the wires to the environment. METEOROLOGICAL INFORMATION At 1153, the weather observation facility located at the William P. Hobby Airport, Houston, Texas, (located 10 miles northeast of the accident site), reported scattered clouds at 3,000 feet, broken layers at 7,000 and 25,000 feet, wind 160 degrees at 7 knots, visibility 10 statue miles, temperature 88 degrees Fahrenheit, dew point 72 degrees Fahrenheit, and altimeter 30.12 inches of Mercury. The remarks section stated that there were rain showers in the vicinity of the airport. Reproduced satellite images were obtained through McIDAS and displayed on an NTSB workstation. At 1215 and 1245, the images revealed only one area of cloud coverage, which was located at the flight path's mid-point. According to cloud to ground lightening strike data, provided by Global Atmospherics, Inc., during the period between 1226 to 1231 there were no cloud to ground lightening strikes within 10 nautical miles of the accident location. Furthermore, no thunderstorms were in the accident site vicinity at the time of the accident. WRECKAGE AND IMPACT INFORMATION A global positioning satellite (GPS) receiver located the accident site at North 29 degrees 34.33 minutes latitude, and West 095 degrees 26.24 minutes longitude. The fuselage of the helicopter came to rest on a measured magnetic heading of 190 degrees, 635 feet southwest of the fueling facility. Ground scars at the accident site revealed that the helicopter initially impacted the ground on the left side of the fuselage in a near inverted position, and then came to rest upright 26 feet southeast of the initial ground impact point. The transmission and main rotor assembly remained secured to each other, but separated from the engines and airframe and came to rest 19.6 feet south of the fuselage. The four main rotor blades were found separated from the main rotor hub (rotor star). One main rotor blade (red) was located 686 feet west of the fuselage, a second blade (blue) was located 275 feet north of the fuselage, a third blade (yellow) was located 329 feet north of the fuselage, and the fourth blade (green) was located 237 feet east of the fuselage. The yellow main rotor blade, the inner sleeve assembly, the blade mounting fork, and the control lever (pitch horn) remained secured to each other. The T-T strap, serial number 5050, which secures the yellow main rotor blade to the rotor star by way of a quadruple nut and retaining pin in the rotor star and a retaining nut in the blade mounting fork, was separated in two sections. The quadruple nut was found secured within the rotor star and the outer retaining nut was found secured to the blade mounting ## Aircraft - Registration: [N110HH](https://openairdocs.org/deregistered/N110HH-2000-05-11), registration cancelled 2000-05-11, S/N 7122 (OpenAirDocs) - Reported make and model: MBB BK-117-B2 - Registry model: [Messerschmitt-Bolkow-Blohm BK 117 A-4](https://openairdocs.org/model/messerschmitt-bolkow-blohm-bk-117-a-4) (registry code 5626017) (OpenAirDocs) - Category: Helicopter - Serial number: 7122 - Airframe hours: 7815 - Engines: Honeywell LTS101-750B-1 592 horsepower turbo shaft - Damage: Destroyed - Flight: Positioning, Part 91 - Registered owner: Hermann Memorial Hospital Sys - Airworthiness certificate: Standard, Transport - Last inspection: AAIP, July 7, 1999, 25 hours before - Departed: 20TA, HOUSTON, TX - Destination: TE11, FRESNO, TX - Flight plan: Company VFR - Airport: TE11, Lifeflight Refuel ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 58; commercial, airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--no waivers/lim.; seat: right; toxicology performed; flight hours: 9,233 total, 9,233 as pilot in command, 33 in the last 90 days, 22 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 160° at 7 knots - Visibility: 10 statute miles - Lowest ceiling: 7,000 ft broken - Temperature: 88 °F, dew point 75 °F - Altimeter: 30.00 inHg - Observed at: HOU, 10 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 19990717009089A](https://openairdocs.org/incident/19990717009089A), Jul 17, 1999: Bolkms BK117B2, Houston, TX, Destroyed, 3 fatal. Air taxi, lifeflight crashed with three fatalities (other circumstances are unknown) near fresno, TX. (.19)on July 17, 1999, at 1231 central daylight time, a… ## Docket (60 files) The files NTSB released with the investigation on April 19, 2001, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=46849. 15.7 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 523 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452444&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Supplement S (item 2, .PDF, 57 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136713&FileExtension=.PDF&FileName=Supplement%20S-Master.PDF - Materials Laboratory Factual Report (item 3, .PDF, 742 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452455&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report-Redacted.PDF - Materials Laboratory Factual Report, Figures 1 & 2 (item 4, .PDF, 38 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136715&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figures%201%20%26%202-Master.PDF - Materials Laboratory Factual Report, Figures 3 & 4 (item 5, .PDF, 32 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136716&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figures%203%20%26%204-Master.PDF - Materials Laboratory Factual Report, Figures 5 & 6 (item 6, .PDF, 40 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136717&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figures%205%20%26%206-Master.PDF - Materials Laboratory Factual Report, Figures 7 & 8 (item 7, .PDF, 35 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136718&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figures%207%20%26%208-Master.PDF - Materials Laboratory Factual Report, Figures 9 & 10 (item 8, .PDF, 31 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136719&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figures%209%20%26%2010%20-Master.PDF - Materials Laboratory Factual Report, Figures 11 & 12 (item 9, .PDF, 39 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136720&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figures%2011%20%26%2012%20-Master.PDF - Materials Laboratory Factual Report, Figures 13 & 14 (item 10, .PDF, 35 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136721&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figures%2013%20%26%2014-Master.PDF - Materials Laboratory Factual Report, Figures 15 & 16 (item 11, .PDF, 43 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136722&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figures%2015%20%26%2016-Master.PDF - Materials Laboratory Factual Report, Figures 17 & 18 (item 12, .PDF, 35 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136723&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figures%2017%20%26%2018-Master.PDF - Materials Laboratory Factual Report, Figure 19 (item 13, .PDF, 29 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136724&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figure%2019-Master.PDF - NTSB Meteorology Factual Report Attachments (item 14, .PDF, 740 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136725&FileExtension=.PDF&FileName=NTSB%20Meteorology%20Factual%20Report%20%20Attachments-Master.PDF - NTSB Meteorology Factual Report, Attachment 3 (item 15, .PDF, 46 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136726&FileExtension=.PDF&FileName=NTSB%20Meteorology%20Factual%20Report,%20Attachment%203-Master.PDF - NTSB Meteorology Factual Report, Attachment 3 (item 16, .PDF, 43 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136727&FileExtension=.PDF&FileName=NTSB%20Meteorology%20Factual%20Report,%20Attachment%203-Master.PDF - NTSB Meteorology Factual Report, Attachment 4 (item 17, .PDF, 47 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136728&FileExtension=.PDF&FileName=NTSB%20Meteorology%20Factual%20Report,%20Attachment%204-Master.PDF - NTSB Meteorology Factual Report, Attachment 4 (item 18, .PDF, 44 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136729&FileExtension=.PDF&FileName=NTSB%20Meteorology%20Factual%20Report,%20Attachment%204-Master.PDF - Witness Statements (item 19, .PDF, 158 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452445&FileExtension=.PDF&FileName=Witness%20Statements-Redacted.PDF - Wreckage Distribution Diagrams (item 20, .PDF, 175 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136732&FileExtension=.PDF&FileName=Wreckage%20Distribution%20Diagrams-Master.PDF - Report From Party to the Investigation (Honeywell) (item 21, .PDF, 727 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452446&FileExtension=.PDF&FileName=Report%20From%20Party%20to%20the%20Investigation%20(Honeywell)-Redacted.PDF - Report from Party to the Investigation (Honeywell), Figures 1 & 2 (item 22, .PDF, 41 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136734&FileExtension=.PDF&FileName=Report%20from%20Party%20to%20the%20Investigation%20(Honeywell),%20Figures%201%20%26%202-Master.PDF - Report from Party to the Investigation (Honeywell), Figures 5 & 6 (item 23, .PDF, 35 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136735&FileExtension=.PDF&FileName=Report%20from%20Party%20to%20the%20Investigation%20(Honeywell),%20Figures%205%20%26%206-Master.PDF - Report from Party to the Investigation (Honeywell), Figures 7 & 8 (item 24, .PDF, 32 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136736&FileExtension=.PDF&FileName=Report%20from%20Party%20to%20the%20Investigation%20(Honeywell),%20Figures%207%20%26%208-Master.PDF - Report from Party to the Investigation (Honeywell), Figures 9 & 10 (item 25, .PDF, 33 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136737&FileExtension=.PDF&FileName=Report%20from%20Party%20to%20the%20Investigation%20(Honeywell),%20Figures%209%20%26%2010%20-Master.PDF - Report from Party to the Investigation (Honeywell), Figures 13 & 14 (item 26, .PDF, 37 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136738&FileExtension=.PDF&FileName=Report%20from%20Party%20to%20the%20Investigation%20(Honeywell),%20Figures%2013%20%26%2014-Master.PDF - Report from Party to the Investigation (Honeywell), Figures 21 & 22 (item 27, .PDF, 42 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136739&FileExtension=.PDF&FileName=Report%20from%20Party%20to%20the%20Investigation%20(Honeywell),%20Figures%2021%20%26%2022-Master.PDF - Report from Party to the Investigation (Honeywell), Figures 23 & 24 (item 28, .PDF, 45 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136740&FileExtension=.PDF&FileName=Report%20from%20Party%20to%20the%20Investigation%20(Honeywell),%20Figures%2023%20%26%2024-Master.PDF - Report from Party to the Investigation (Honeywell), Figures 31 & 32 (item 29, .PDF, 34 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136741&FileExtension=.PDF&FileName=Report%20from%20Party%20to%20the%20Investigation%20(Honeywell),%20Figures%2031%20%26%2032-Master.PDF - Report from Party to the Investigation (Honeywell), Figures 33 & 34 (item 30, .PDF, 38 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136742&FileExtension=.PDF&FileName=Report%20from%20Party%20to%20the%20Investigation%20(Honeywell),%20Figures%2033%20%26%2034%20-Master.PDF - Report from Party to the Investigation (Honeywell), Figures 37 & 38 (item 31, .PDF, 35 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136743&FileExtension=.PDF&FileName=Report%20from%20Party%20to%20the%20Investigation%20(Honeywell),%20Figures%2037%20%26%2038%20-Master.PDF - Report from Federal Agency (Hobby ATCT) (item 32, .PDF, 95 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452447&FileExtension=.PDF&FileName=Report%20from%20Federal%20Agency%20(Hobby%20ATCT)-Redacted.PDF - Radar Data (item 33, .PDF, 302 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452448&FileExtension=.PDF&FileName=Radar%20Data-Redacted.PDF - Dispatch Data From Hermann Hospital (item 34, .PDF, 149 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452449&FileExtension=.PDF&FileName=Dispatch%20Data%20From%20Hermann%20Hospital-Redacted.PDF - Pilot Records (item 35, .PDF, 895 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452450&FileExtension=.PDF&FileName=Pilot%20Records-Redacted.PDF - Excerpts From Engine Maintenance Records (item 36, .PDF, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452451&FileExtension=.PDF&FileName=Excerpts%20From%20Engine%20Maintenance%20Records-Redacted.PDF - Excerpts From MBB BK-117 Training Manual & IPC (item 37, .PDF, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136749&FileExtension=.PDF&FileName=Excerpts%20From%20MBB%20BK-117%20Training%20Manual%20%26%20IPC-Master.PDF - Excerpts from Airframe Maintenance Records (item 38, .PDF, 5.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452452&FileExtension=.PDF&FileName=Excerpts%20from%20Airframe%20Maintenance%20Records-Redacted.PDF - Pertinent Airworthiness Directives (item 39, .PDF, 714 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136751&FileExtension=.PDF&FileName=Pertinent%20Airworthiness%20Directives-Master.PDF - Toxicological Report (item 40, .PDF, 67 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452453&FileExtension=.PDF&FileName=Toxicological%20Report-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 41, .PDF, 222 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452454&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF - Photo 1: Aerial view of the accident site. (No Neg.) (item 42, .PDF, 51 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136754&FileExtension=.PDF&FileName=Photo%201%3A%20%20Aerial%20view%20of%20the%20accident%20site.%20%20(No%20Neg.)-Master.PDF - Photo 2: View of the left side of the helicopter. (item 43, .PDF, 37 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136755&FileExtension=.PDF&FileName=Photo%202%3A%20%20View%20of%20the%20left%20side%20of%20the%20helicopter.-Master.PDF - Photo 3: View of the right side of the helicopter. (item 44, .PDF, 63 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136756&FileExtension=.PDF&FileName=Photo%203%3A%20%20View%20of%20the%20right%20side%20of%20the%20helicopter.%20%20-Master.PDF - Photo 4: View of nose of helicopter & separated transmission & main rotor hub (see arrow). (item 45, .PDF, 57 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136757&FileExtension=.PDF&FileName=Photo%204%3A%20%20View%20of%20nose%20of%20helicopter%20%26%20separated%20transmission%20%26%20main%20rotor%20hub%20(see%20arrow).%20%20-Master.PDF - Photo 5: View of transmission & main rotor head. Arrow points to the blade sleeve for the yellow main rotor blade. (No Neg.) (item 46, .PDF, 65 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136758&FileExtension=.PDF&FileName=Photo%205%3A%20%20View%20of%20transmission%20%26%20main%20rotor%20head.%20%20Arrow%20points%20to%20the%20blade%20sleeve%20for%20the%20yellow%20main%20rotor%20blade.%20%20(No%20Neg.)%20%20-Master.PDF - Photo 6: Close-up view of the blade sleeve for the yellow main rotor blade. Note lack of deformation. (item 47, .PDF, 57 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136759&FileExtension=.PDF&FileName=Photo%206%3A%20%20Close-up%20view%20of%20the%20blade%20sleeve%20for%20the%20yellow%20main%20rotor%20blade.%20%20Note%20lack%20of%20deformation.%20%20-Master.PDF - Photo 7: Another view of the transmission & main rotor head. (item 48, .PDF, 72 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136760&FileExtension=.PDF&FileName=Photo%207%3A%20%20Another%20view%20of%20the%20transmission%20%26%20main%20rotor%20head.%20%20-Master.PDF - Photo 8: View of yellow main rotor at accident site. (item 49, .PDF, 64 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136761&FileExtension=.PDF&FileName=Photo%208%3A%20%20View%20of%20yellow%20main%20rotor%20at%20accident%20site.%20%20-Master.PDF - Photo 9: View of yellow main rotor blade being extricated from the ground. Note frayed T-T strap. (item 50, .PDF, 65 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136762&FileExtension=.PDF&FileName=Photo%209%3A%20%20View%20of%20yellow%20main%20rotor%20blade%20being%20extricated%20from%20the%20ground.%20%20Note%20frayed%20T-T%20strap.%20%20-Master.PDF - Photo 10: Close-up view of the inner sleeve, blade mounting fork & separated T-T strap after extrication from the ground. (item 51, .PDF, 84 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136763&FileExtension=.PDF&FileName=Photo%2010%3A%20%20Close-up%20view%20of%20the%20inner%20sleeve,%20blade%20mounting%20fork%20%26%20separated%20T-T%20strap%20after%20extrication%20from%20the%20ground.%20%20-Master.PDF - Photo 11: View of T-T strap & blade mounting fork after removal from the main rotor blade. (item 52, .PDF, 83 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136764&FileExtension=.PDF&FileName=Photo%2011%3A%20%20View%20of%20%20T-T%20strap%20%26%20blade%20mounting%20fork%20after%20removal%20from%20the%20main%20rotor%20blade.%20%20-Master.PDF - Photo 12: View of the T-T strap at the attaching point w/the blade mounting fork, after disassembly. (item 53, .PDF, 38 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136765&FileExtension=.PDF&FileName=Photo%2012%3A%20%20View%20of%20the%20T-T%20strap%20at%20the%20attaching%20point%20w%2Fthe%20blade%20mounting%20fork,%20after%20disassembly.%20%20-Master.PDF - Photo 13: View of main rotor head. (item 54, .PDF, 48 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136766&FileExtension=.PDF&FileName=Photo%2013%3A%20%20View%20of%20main%20rotor%20head.%20%20-Master.PDF - Photo 14: View of the T-T strap. (item 55, .PDF, 46 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136767&FileExtension=.PDF&FileName=Photo%2014%3A%20%20View%20of%20the%20T-T%20strap.-Master.PDF - Photo 15: View of all T-T straps from the accident helicopter. (item 56, .PDF, 44 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136768&FileExtension=.PDF&FileName=Photo%2015%3A%20%20View%20of%20all%20T-T%20straps%20from%20the%20accident%20helicopter.%20%20-Master.PDF - Photo 16: View of fractured outer needle bearing assembly. (item 57, .PDF, 33 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136769&FileExtension=.PDF&FileName=Photo%2016%3A%20%20View%20of%20fractured%20outer%20needle%20bearing%20assembly.%20%20-Master.PDF - Photo 17: The T-T strap after disassembly. (No Neg.) (item 58, .PDF, 40 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136770&FileExtension=.PDF&FileName=Photo%2017%3A%20%20The%20T-T%20strap%20after%20disassembly.%20%20(No%20Neg.)-Master.PDF - Photo 18: View looking into the black sleeve (outer needle bearing assembly) at separated portion of T-T strap. (No Neg.) (item 59, .PDF, 48 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136771&FileExtension=.PDF&FileName=Photo%2018%3A%20%20View%20looking%20into%20the%20black%20sleeve%20(outer%20needle%20bearing%20assembly)%20at%20separated%20portion%20of%20T-T%20strap.%20%20(No%20Neg.)-Master.PDF - Photo 19: Another view of the T-T strap. (item 60, .PDF, 40 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40136772&FileExtension=.PDF&FileName=Photo%2019%3A%20%20Another%20view%20of%20the%20T-T%20strap.-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.