# NTSB GAA16CA480: Hughes 369, N500TN, Peach Orchard, MO, September 9, 2016 - Type: NTSB accident investigation - Classification: Accident · No injuries · Data collection · Final report - Date: September 9, 2016, 13:00 local (18:00 UTC) - Place: Peach Orchard, MO - Coordinates: 36.328887, -89.938888 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=36.3289&lon=-89.9389&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-hover: Miscellaneous/other](https://openairdocs.org/ntsb-events/900) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report March 13, 2017 - Report: Approved by Office Director - NTSB office: General Aviation Accidents - Parties: FAA - NTSB case key (mKey): 94002 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=GAA16CA480 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/94002/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=94002 - Page: https://openairdocs.org/ntsb/GAA16CA480 ## 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. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Attention/monitoring: monitoring environment](https://openairdocs.org/ntsb-findings/02021545): Personnel issues › Psychological · Pilot (probable cause); cases with it: [Hughes Helicopters HUGHES 369D, 9 cases](https://openairdocs.org/ntsb-findings/02021545/cases.md?model=4470706), [All aircraft, 809 cases](https://openairdocs.org/ntsb-findings/02021545/cases.md) - [Object/animal/substance: wire](https://openairdocs.org/ntsb-findings/03022032): Environmental issues › Physical environment · Effect on operation (probable cause); 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) - [Use of equip/info: use of policy/procedure](https://openairdocs.org/ntsb-findings/02063032): Personnel issues › Task performance · Pilot; cases with it: [Hughes Helicopters HUGHES 369D, 1 case](https://openairdocs.org/ntsb-findings/02063032/cases.md?model=4470706), [All aircraft, 191 cases](https://openairdocs.org/ntsb-findings/02063032/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-hover: Miscellaneous/other](https://openairdocs.org/ntsb-events/900) (defining event); cases with it: [Hughes Helicopters HUGHES 369D, 9 cases](https://openairdocs.org/ntsb-events/900/sequence.md?model=4470706), [All aircraft, 1,556 cases](https://openairdocs.org/ntsb-events/900/sequence.md) ## Analysis The helicopter pilot reported that he was flying in support of a utility company crew that was installing line guards for a conductor damper on an energized 161 kilovolts (Kv) electrical transmission line. The transmission line had three phases (power lines) that were separated vertically and staggered horizontally from one another and ran parallel to the ground. The lower phase power line was about 9.5 ft (horizontally) further out from the middle phase power line. While the helicopter was approaching the lines, its main rotor blade clearance from the middle phase line was about 2.5 ft, which resulted in an electrical arc to the main rotor. The pilot landed the helicopter away from the transmission line without further incident. A postaccident examination revealed substantial damage to the main rotor hub and two main rotor blades. The pilot reported no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation. According to Occupational Safety & Health Administration 1910.269(I)(10), the minimum approach distance (MAD) is to "ensure that workers do not approach or take any conductive object closer to the energized parts as set forth in the table below (excerpt)." For a voltage of 161 Kv, the MAD for this operation was equal to or greater than 4.00625 ft. ## Factual narrative The helicopter pilot reported that he was flying in support of a utility company crew that was installing line guards for a conductor damper on an energized 161 kilovolts (Kv) electrical transmission line. The transmission line had three phases (power lines) that were separated vertically and staggered horizontally from one another and ran parallel to the ground. The lower phase power line was about 9.5 feet (horizontally) further out from the middle phase power line. During approach to the lines, the main rotor blade clearance from the middle phase line was about 2.5 feet, which resulted in an electrical arc to the main rotor. The pilot landed the helicopter away from the transmission line without further incident. A postaccident examination revealed substantial damage to the main rotor hub and two main rotor blades. The pilot reported no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation. According to the Occupational Safety & Health Administration (OSHA) 1910.269(I)(10) the Minimum Approach Distances (MAD) is to "ensure that workers do not approach or take any conductive object closer to the energized parts as set forth in the table below (excerpt). " Nominal voltage in kilovolts Distance: Phase to ground exposure (feet) 161 to 169 4.00625 The MAD for this operation was a distance equal to or greater than 4.00625 feet. ## Aircraft - Registration: [N500TN](https://openairdocs.org/aircraft/N500TN), registered now, S/N 590521D, built 1979 (OpenAirDocs) - Reported make and model: HUGHES 369 (D) - 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 - Year built: 1979 - Airframe hours: 17622.7 - Engines: Rolls Royce 250-C20R 450 horsepower turbo shaft - Damage: Substantial damage - Flight: External load, Part 133 - Operator: Air2 LLC. - Registered owner: Axis Capital - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, September 5, 2016 - Flight plan: Company VFR - Equipment: Electronic flight bag or handheld device, Satellite tracking device, Onboard weather ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 49; injuries: none; commercial; medical: class 2, without waivers/limitations; last flight review March 10, 2015; seat: left; flight hours: 5,750 total, 3,585 in this make and model, 5,475 as pilot in command, 75 in the last 90 days, 37 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 230° at 8 knots, gusting 17 - Visibility: 10 statute miles - Lowest ceiling: 3,700 ft broken - Temperature: 93 °F, dew point 73 °F - Altimeter: 29.95 inHg - Observed at: KTKX, 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 20160909017019A](https://openairdocs.org/incident/20160909017019A), Sep 9, 2016: Hughes 369D, Peach Orchard, MO, Substantial damage. Helicopter was performing part 133 powerline work hovering next to powerlines energized with 161KV. While bonded to one line, another line arced over to the… ## 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 ERA12CA119](https://openairdocs.org/ntsb/ERA12CA119), Dec 21, 2011: Hughes 369D (N500TN), Fall Branch, TN, substantial damage. Probable cause: The pilot's improper decision to continue a visual flight into instrument meteorological conditions, which resulted in a wire strike. ## Docket (4 files) The files NTSB released with the investigation on January 25, 2017, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=94002. 956 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 256 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40455630&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Damage Statement (item 2, .PDF, 48 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40448678&FileExtension=.PDF&FileName=Damage%20Statement-Master.PDF - OSHA - Powerline - Minimum Approach Distance (item 3, .PDF, 155 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40448679&FileExtension=.PDF&FileName=OSHA%20-%20Powerline%20-%20Minimum%20Approach%20Distance-Master.PDF - Accident Photos (Courtesy of Operator) (item 4, .PDF, 2 photos, 497 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40448680&FileExtension=.PDF&FileName=Accident%20Photos%20(Courtesy%20of%20Operator)-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.