# NTSB FTW02LA117: Bell 206B, N513FD, Walnut Hill, TX, April 11, 2002 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: April 11, 2002, 08:00 local (13:00 UTC) - Place: Walnut Hill, TX - Coordinates: 32.846942, -96.851669 - Nearby events: https://openairdocs.org/map.md?lat=32.8469&lon=-96.8517&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 1 minor, 3 uninjured - Status: Completed, report September 30, 2003 - Report: Approved by Office Director - Parties: Bell Helicopter Textron, Rolls-Royce, FAA FSDO - NTSB case key (mKey): 54493 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW02LA117 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/54493/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=54493 - Page: https://openairdocs.org/ntsb/FTW02LA117 ## Probable cause The loss of engine power as a result of the backing off of the PC air line "B" nut due to the improper installation by the company maintenance personnel. Contributing factors were the inadequate preflight by the pilot and the lack of suitable terrain for the forced landing. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power, cruise - fuel system,pc line - loose part/bolt/nut/clamp/etc (cause) - maintenance,installation - improper, company maintenance personnel (cause) - fuel system,pc line - undertorqued - aircraft preflight - inadequate, pilot in command - Forced landing, descent - emergency - autorotation - initiated, pilot in command - Hard landing, landing - flare/touchdown - terrain condition - mountainous/hilly (contributing factor) - object - tree(s) ## Analysis During cruise flight, approximately 400 feet agl, the helicopter experienced a "sudden" loss of power. The pilot initiated an autorotation to a residential street. During the forced landing, the main rotor blades struck trees that over hung the street. Subsequently, the helicopter touched down "hard" and slid to a stop. An examination of the helicopter revealed the B-nut on the PC pneumatic line from the power turbine governor tee fitting to the fuel control, at the fuel control end, was backed off from the fitting. When viewed initially, the B-nut appeared to be connected, but when moved by hand, it dislodged from the fuel control connection. Further examination revealed the whole engine was void of the required torque striping on all B-nuts. Examination of the maintenance records revealed the helicopter accumulated 42.6 hours since the last 100-hour maintenance inspection that was performed on March 29, 2002. ## Factual narrative On April 11, 2002, at 0800 central daylight time, a Bell 206B helicopter, N513FD, was substantially damaged during a forced landing following a loss of engine power near Walnut Hill, Texas. The helicopter was registered to Heartland Helicopter Leasing of Rogersville, Missouri, and operated by Sky One Helicopters of Fort Worth, Texas. The airline transport pilot and two passengers were not injured, and one passenger sustained minor injuries. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 traffic reporting flight. The flight originated from the Dallas Love Field Airport, Dallas, Texas, at 0550. According to information obtained in the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) the helicopter experienced a "sudden" loss of power while at approximately 400 feet agl. The pilot initiated an autorotation to a residential street. During the forced landing, the main rotor blades struck trees, which over hung the street. Subsequently, the helicopter touched down "hard" and slid to a stop. An examination of the helicopter, by an FAA inspector who responded to the accident site, revealed that the helicopter's tail boom had separated aft of the horizontal stabilizer, one main rotor blade was damaged, and the landing skids were spread. Further examination of the helicopter on April 16, 2002, at Air Salvage of Dallas in Lancaster, Texas, under supervision of the NTSB, revealed the B-nut on the PC pneumatic line from the power turbine governor tee fitting to the fuel control, at the fuel control end, was backed off from the fitting. When viewed initially, the B-nut appeared to be connected, but when moved by hand, it dislodged from the fuel control connection. The cushioned clamp on this same line was not fastened to anything. Further examination revealed the engine was void of the required torque striping on all B-nuts. According to the Rolls-Royce Allison 250C20 Series Operation and Maintenance manual, paragraph 9.B., "when proper free state alignment is attained, complete tubing installation by simultaneously securing the coupling nuts. After all B-nuts are properly tightened to the correct torque values, apply a slippage mark (torque paint) of contrasting color approximately 0.063 inch (1.60mm) wide minimum. The mark shall extend down the side of the B-nut and onto the mating fitting. Install necessary clamping." Examination of the maintenance records revealed the helicopter accumulated 42.6 hours since the last 100-hour maintenance inspection that was performed on March 29, 2002. The required inspections of this system are noted in table 602 of the Rolls-Royce Allison 250C20 Series Operation and Maintenance manual, under the "100 hour inspection checklist" section, it is noted to "inspect all "B" nuts for application and alignment of torque paint. If missing, loosen "B" nut, retighten, and apply torque paint." Also indicated in the Bell 206B Flight Manual, section 2, during the exterior preflight, the pneumatic lines should be checked for overall condition and security. ## Aircraft - Registration: [N513FD](https://openairdocs.org/deregistered/N513FD-2018-01-17), registration cancelled 2018-01-17, S/N 891, built 1972 (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-C20 series](https://openairdocs.org/engine/allison-250-c20-series) (registry code 03020, turbo-prop) (OpenAirDocs) - Category: Helicopter - Serial number: 891 - Airframe hours: 5056.7 - Engines: Rolls-Royce 250-C20 400 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial observation, Part 91 - Operator: Sky One Helicopters - Registered owner: Heartland Helicopter leasing - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, March 29, 2002, 42.6 hours before - Departed: DAL, Dallas, TX ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 50; injuries: none; flight instructor, commercial, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane, helicopter; medical: class 2, valid medical--w/ waivers/lim; last flight review April 24, 2000; seat: right; toxicology performed; flight hours: 8,000 total, 4,000 in this make and model, 7,000 as pilot in command, 300 in the last 90 days, 100 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 170° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 64 °F ## 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 20020411007419A](https://openairdocs.org/incident/20020411007419A), Apr 11, 2002: Bell 206B, Dallas, TX, No damage. (-23) On April 11, 2002, at approximately 0800 hrs. Mr. David myer was operating Bell 206B helicopter N513FD on a traffic watch flight with three additional… ## Docket (9 files) The files NTSB released with the investigation on July 31, 2003, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=54493. 12.3 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 731 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40428430&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Reports from Parties to the Investigation - Bell Helicopter (item 2, .PDF, 7 photos, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40428431&FileExtension=.PDF&FileName=Reports%20from%20Parties%20to%20the%20Investigation%20-%20Bell%20Helicopter-Redacted.PDF - Reports from Parties to the Investigation - Rolls Royce (item 3, .PDF, 12 photos, 7.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40428432&FileExtension=.PDF&FileName=Reports%20from%20Parties%20to%20the%20Investigation%20-%20Rolls%20Royce-Redacted.PDF - Aircraft Flight Manual (Excerpts) (item 4, .PDF, 304 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40428433&FileExtension=.PDF&FileName=Aircraft%20Flight%20Manual%20(Excerpts)-Redacted.PDF - Maintenance Manual Volume 1 (Excerpts) (item 5, .PDF, 717 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40428434&FileExtension=.PDF&FileName=Maintenance%20Manual%20Volume%201%20(Excerpts)-Redacted.PDF - Rigid Tubing Information and Inspection Checklist (item 6, .PDF, 640 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40428435&FileExtension=.PDF&FileName=Rigid%20Tubing%20Information%20and%20Inspection%20Checklist-Redacted.PDF - Warnings and Cautions for Rigid Tubing Installations (item 7, .PDF, 72 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40188031&FileExtension=.PDF&FileName=Warnings%20and%20Cautions%20for%20Rigid%20Tubing%20Installations-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 8, .PDF, 333 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40428436&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 9, .PDF, 125 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40428437&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-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.