# NTSB ERA12CA119: Hughes 369D, N500TN, Fall Branch, TN, December 21, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Data collection · Final report - Date: December 21, 2011, 16:15 local (21:15 UTC) - Place: Fall Branch, TN - Coordinates: 36.419723, -82.589447 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=36.4197&lon=-82.5894&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: VFR encounter with IMC](https://openairdocs.org/ntsb-events/401) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report March 27, 2012 - Report: Approved by Office Director - NTSB office: Eastern Region Aviation - Parties: FAA / FSDO - NTSB case key (mKey): 82553 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA12CA119 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/82553/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=82553 - Page: https://openairdocs.org/ntsb/ERA12CA119 ## Probable cause The pilot's improper decision to continue a visual flight into instrument meteorological conditions, which resulted in a wire strike. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Info processing/decision: decision making/judgment](https://openairdocs.org/ntsb-findings/02041520): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Hughes Helicopters HUGHES 369D, 6 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md?model=4470706), [All aircraft, 3,098 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md) - [Object/animal/substance: wire](https://openairdocs.org/ntsb-findings/03022032): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Hughes Helicopters HUGHES 369D, 11 cases](https://openairdocs.org/ntsb-findings/03022032/cases.md?model=4470706), [All aircraft, 588 cases](https://openairdocs.org/ntsb-findings/03022032/cases.md) - [Ceiling/visibility/precip](https://openairdocs.org/ntsb-findings/03035000): Environmental issues › Conditions/weather/phenomena · Effect on operation; cases with it: [Hughes Helicopters HUGHES 369D, 1 case](https://openairdocs.org/ntsb-findings/03035000/cases.md?model=4470706), [All aircraft, 65 cases](https://openairdocs.org/ntsb-findings/03035000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute: VFR encounter with IMC](https://openairdocs.org/ntsb-events/401) (defining event); cases with it: [Hughes Helicopters HUGHES 369D, 2 cases](https://openairdocs.org/ntsb-events/401/sequence.md?model=4470706), [All aircraft, 392 cases](https://openairdocs.org/ntsb-events/401/sequence.md) - [Enroute: Controlled flight into terr/obj (CFIT)](https://openairdocs.org/ntsb-events/120); cases with it: [Hughes Helicopters HUGHES 369D, 9 cases](https://openairdocs.org/ntsb-events/120/sequence.md?model=4470706), [All aircraft, 1,074 cases](https://openairdocs.org/ntsb-events/120/sequence.md) ## Analysis Prior to departure on a positioning flight, the pilot checked the weather and determined that visual meteorological conditions existed at both his departure and destination airports. However, while the pilot was following a highway in cruise flight at 400 feet above ground level, the ceiling rapidly became lower, and the pilot encountered instrument meteorological conditions. Moments later, while cruising at an airspeed of 65 knots, the pilot saw marker balls, which indicated that power lines were directly in front of the helicopter. The pilot lowered the collective and entered a right diving turn in order to avoid the wires, but one of the main rotor blades made contact. The rotor speed remained within limits, but the helicopter began to vibrate, so the pilot decided to land in a nearby field. Postaccident examination of the helicopter revealed that the main rotor blade that had made contact with the power line was substantially damaged. ## Factual narrative Prior to departure on a positioning flight, the pilot of the helicopter checked the weather and determined that visual meteorological conditions existed at both his departure and destination airports. However, while in cruise flight at 400 feet above ground level while following a highway, the ceiling rapidly became lower, and the pilot encountered instrument meteorological conditions. Moments later at an airspeed of 65 knots, marker balls appeared which indicated that power lines were directly in front of him. He lowered the collective and entered a right diving turn in order to avoid the wires but one of his main rotor blades made contact with a power line. The rotor speed remained within limits but the helicopter began to vibrate. As a result, the pilot decided to land in a nearby field. Post accident examination of the helicopter revealed that the main rotor blade that had made contact with the power line was substantially damaged. ## Aircraft - Registration: [N500TN](https://openairdocs.org/aircraft/N500TN), registered now, S/N 590521D, built 1979 (OpenAirDocs) - Reported make and model: HUGHES 369D - Registry model: [Hughes Helicopters HUGHES 369D](https://openairdocs.org/model/hughes-helicopters-hughes-369d) (registry code 4470706) (OpenAirDocs) - Registry engine: [Rolls-Royce 250-C20B](https://openairdocs.org/engine/rolls-royce-250-c20b) (registry code 54385, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 590521D - Airframe hours: 14193 - Engines: ROLLS-ROYCE 250-C20R/2 450 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial observation, Part 91 - Operator: Air 2 LLC - Registered owner: Air 2 LLC - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, December 5, 2011 - Departed: DXX, Knoxville, TN - Destination: KTRI, Blountville, TN - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 32; injuries: none; commercial, flight instructor; instrument ratings: helicopter; medical: class 2, without waivers/limitations; last flight review January 21, 2011; seat: left; flight hours: 2,337 total, 400 in this make and model, 2,387 as pilot in command, 220 in the last 90 days, 70 in the last 30 days, 7 in the last 24 hours ## Weather - Conditions: Instrument (IMC), Day - Wind: 230° at 10 knots - Visibility: 1 statute miles - Lowest ceiling: 400 ft overcast - Temperature: 61 °F, dew point 57 °F - Altimeter: 29.89 inHg ## 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 20111221029959A](https://openairdocs.org/incident/20111221029959A), Dec 21, 2011: Hughes 369D, Fall Branch, TN, Minor damage. The pilot departed kdkx (down town island airport), knoxville, TN, enroute to ktri (ti-cities regional airport) on a course of 072 degrees at 400 ft AGL at… ## Other investigations on N500TN (1) 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 GAA16CA480](https://openairdocs.org/ntsb/GAA16CA480), Sep 9, 2016: Hughes 369 (N500TN), Peach Orchard, MO, substantial damage. Probable cause: The helicopter pilot’s failure to maintain sufficient separation between the main rotor blade and a power line during line guard installation, which resulted in an electrical arc to the main rotor. ## Docket (9 files) The files NTSB released with the investigation on January 31, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=82553. 17.4 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 791 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361653&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Aircraft Three View Drawing (DOD) (item 2, .PDF, 31 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361648&FileExtension=.PDF&FileName=Aircraft%20Three%20View%20Drawing%20(DOD)-Master.PDF - Witness Statements and Interview Summaries (item 3, .PDF, 50 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361649&FileExtension=.PDF&FileName=Witness%20Statements%20and%20Interview%20Summaries-Master.PDF - Weather Reports and Records (KTRI Metars) (item 4, .PDF, 105 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361650&FileExtension=.PDF&FileName=Weather%20Reports%20and%20Records%20(KTRI%20Metars)-Master.PDF - Photograph of Helicopter in Field (FAA) (item 5, .PDF, 3.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361654&FileExtension=.PDF&FileName=Photograph%20of%20Helicopter%20in%20Field%20(FAA)-Master.PDF - Photograph of Damaged Main Rotor Blade (FAA) (item 6, .PDF, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361655&FileExtension=.PDF&FileName=Photograph%20of%20Damaged%20Main%20Rotor%20Blade%20(FAA)-Master.PDF - Side View Photograph of Damaged Main Rotor Blade (FAA) (item 7, .PDF, 1.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361656&FileExtension=.PDF&FileName=Side%20View%20Photograph%20of%20Damaged%20Main%20Rotor%20Blade%20(FAA)-Master.PDF - Spanwise Photograph of Damaged Main Rotor Blade (FAA) (item 8, .PDF, 5.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361657&FileExtension=.PDF&FileName=Spanwise%20Photograph%20of%20Damaged%20Main%20Rotor%20Blade%20(FAA)-Master.PDF - Photograph of Initial Impact Point on Damaged Main Rotor Blade (FAA) (item 9, .PDF, 2.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361658&FileExtension=.PDF&FileName=Photograph%20of%20Initial%20Impact%20Point%20on%20Damaged%20Main%20Rotor%20Blade%20(FAA)-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.