# NTSB WPR18CA100: Hughes 369D, N501VS, Pacific Ocean, Marshall Islands, February 19, 2018 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Data collection · Final report - Date: February 19, 2018 - Place: Pacific Ocean, Marshall Islands - Coordinates: 34.979999, 159.979995 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.9800&lon=159.9800&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) - Highest injury: Minor injuries - Injuries: 2 minor - Status: Completed, report June 29, 2020 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 96831 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR18CA100 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/96831/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=96831 - Page: https://openairdocs.org/ntsb/WPR18CA100 ## Probable cause An in-flight mechanical malfunction with the helicopter, which necessitated a ditching in the ocean. The reason for the malfunction could be determined because the helicopter sank and was not recovered. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Hughes Helicopters HUGHES 369D, 8 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=4470706), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) - [Terrain: water](https://openairdocs.org/ntsb-findings/03021020): Environmental issues › Physical environment · Contributed to outcome (probable cause); cases with it: [Hughes Helicopters HUGHES 369D, 2 cases](https://openairdocs.org/ntsb-findings/03021020/cases.md?model=4470706), [All aircraft, 97 cases](https://openairdocs.org/ntsb-findings/03021020/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-low-alt flying: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) (defining event); cases with it: [Hughes Helicopters HUGHES 369D, 3 cases](https://openairdocs.org/ntsb-events/000/sequence.md?model=4470706), [All aircraft, 1,703 cases](https://openairdocs.org/ntsb-events/000/sequence.md) - [Landing: Ditching](https://openairdocs.org/ntsb-events/441); cases with it: [Hughes Helicopters HUGHES 369D, 1 case](https://openairdocs.org/ntsb-events/441/sequence.md?model=4470706), [All aircraft, 186 cases](https://openairdocs.org/ntsb-events/441/sequence.md) - [Landing: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Hughes Helicopters HUGHES 369D, 26 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=4470706), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) - [Landing: Roll over](https://openairdocs.org/ntsb-events/097); cases with it: [Hughes Helicopters HUGHES 369D, 3 cases](https://openairdocs.org/ntsb-events/097/sequence.md?model=4470706), [All aircraft, 261 cases](https://openairdocs.org/ntsb-events/097/sequence.md) ## Analysis The pilot departed for a flight over the open ocean. About 1 hour into the flight, the pilot descended the helicopter to sea level to attach a GPS buoy to a log. After attaching the buoy and as the helicopter was climbing through 400 to 500 ft above the water, the pilot heard a bang come from the area of the rotor head, followed by the cyclic control shaking. The pilot contacted support vessel personnel, notified them of the issue, and proceeded in the vessel's direction, but the helicopter continued experiencing intermittent flight control problems and was unable to reach the vessel. The pilot attempted to deploy the inflatable floats; however, they did not deploy. The pilot subsequently initiated a ditching, and the helicopter impacted water and rolled inverted. The pilot and passenger egressed the helicopter, which then sank, and the helicopter was not recovered. ## Factual narrative The pilot and passenger departed on a fish survey flight over the open ocean. About an hour into the flight, a descent was made to sea level to attach a GPS buoy on a log. After attaching the buoy, the helicopter was climbing through 400-500 ft, when the pilot heard a bang come from the area of the rotor head, followed by a shake in the cyclic control. The pilot radioed the support vessel notifying them of the issue and proceeded to head in their direction. The pilot continued to experience intermittent flight control problems, and unable to reach the vessel, attempted to deploy the inflatable floats, however they did not deploy. The pilot subsequently declared a mayday and initiated a forced water landing. After the helicopter impacted the water, it rolled inverted. The pilot and passenger egressed before the helicopter sank. The helicopter was not recovered. ## Aircraft - Registration: [N501VS](https://openairdocs.org/aircraft/N501VS), registered now, S/N 170050D, built 1977 (OpenAirDocs) - Reported make and model: HUGHES 369D (D) - Registry model: [Hughes Helicopters HUGHES 369D](https://openairdocs.org/model/hughes-helicopters-hughes-369d) (registry code 4470706) (OpenAirDocs) - Registry engine: [Allison 250-C20B](https://openairdocs.org/engine/allison-250-c20b) (registry code 03081, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 170050D - Year built: 1977 - Airframe hours: 18502.5 - Engines: Rolls Royce 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial observation, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, December 19, 2017, 79 hours before - Departed: Marshall Island - Destination: Marshall Islands ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 26; injuries: minor; commercial; medical: class 2, with waivers/limitations; seat: left; restraint: 4-point; flight hours: 0 total, 0 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 270° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 88 °F ## Docket (2 files) The files NTSB released with the investigation on April 20, 2018, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=96831. 2.9 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 2.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40462145&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Pilot's Statement (item 2, .PDF, 501 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40483208&FileExtension=.PDF&FileName=Pilot%27s%20Statement-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.