# NTSB SEA02TA022: Hughes 369D, N8393F, Butte, MT, January 3, 2002 - Type: NTSB accident investigation - Classification: Accident · No injuries · Final report - Date: January 3, 2002, 14:50 local (21:50 UTC) - Place: Butte, MT - Coordinates: 45.958057, -112.483329 - Nearby events: https://openairdocs.org/map.md?lat=45.9581&lon=-112.4833&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report April 8, 2003 - Report: Approved by Office Director - Parties: NTSB, Rolls-Royce Corp, FAA-FSDO, Montana Fish and Wildlife - NTSB case key (mKey): 53985 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA02TA022 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/53985/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=53985 - Page: https://openairdocs.org/ntsb/SEA02TA022 ## Probable cause Loss of engine power for undetermined reasons. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power, cruise - reason for occurrence undetermined (cause) - Forced landing, emergency descent/landing - autorotation - performed, pilot in command - In flight collision with terrain/water, emergency descent/landing ## Analysis While returning from a flight at about 600-800 feet above ground level, the engine lost power. The pilot autorotated the helicopter to a median between a highway. During the event, the tailboom was severed. Post accident inspection of the engine and subsequent engine test cell run did not find evidence of a mechanical failure or malfunction. ## Factual narrative On January 3, 2002, approximately 1450 mountain standard time, a Hughes 369D helicopter, N8393F, being operated by the Montana State Department of Fish, Wildlife, and Parks on a public-use aerial deer count flight, experienced a loss of engine power at approximately 600 feet above ground level while en route to Bert Mooney Field, Butte, Montana. The commercial pilot-in-command executed an autorotation to a forced landing on the median of Interstate Highway 90 (I-90) about 5 miles west of Butte. The pilot and one mission crewmember (a wildlife biologist) were not injured, but the helicopter was substantially damaged when its tail boom separated during the forced landing. Instrument meteorological conditions (ceiling 1,200 feet overcast, visibility 3/4 statute mile in light snow and mist) were reported at Butte at 1453. A company flight plan was in effect for the flight. In a written statement, the pilot reported that the wildlife survey flight lasted about 1 hour and 30 minutes. The flight was returning to Butte, when the engine "failed." The pilot autorotated the helicopter to the medium of the interstate in a tail low attitude. The helicopter spun around 180 degrees after landing which during the event, the tail boom was severed. The pilot reported that there were no unusual indications that preceded the engine out; the engine anti-ice was on for the entire flight; the fuel ice filter was installed and operational; the intake filter "clogged" warning light was operational and the cabin heat was on medium setting. The pilot also stated that when the engine failed, he recalled that the engine out light and the auto re-ignition light illuminated. The helicopter was in cruise flight at about 100 knots and about 600 to 800 feet above ground level. The pilot reported at the time, that the visibility was one-and-a-half to two miles visibility with light snow falling. Investigators from the FAA, Boeing Helicopters (current holder of the Hughes 369D type certificate), Rolls-Royce USA (formerly Allison Engines), and the Montana State Department of Fish, Wildlife, and Parks examined the helicopter at the facilities of the Montana State Department of Fish, Wildlife, and Parks on January 8, 2002. These investigators determined that an adequate quantity of fuel was aboard the helicopter at the time of the accident. The engine was transported to Rolls-Royce, Indianapolis, Indiana, for examination and test run. On February 12, 2002, in the presence of a Federal Aviation Administration Inspector. The inspector reported that after the engine was removed from the crate, it was visually examined for damage. The inspector reported no discrepancies or damage was evident. The engine was then prepared for a test cell run. The engine was then started and warmed up. After warm-up, the engine was put through a normal acceptance test run and all parameters were checked and recorded. The inspector reported that, "At the high and mid cruise horsepower (HP) settings, the engine was slightly below the HP that Rolls-Royce would accept for a NEW engine." No other discrepancies were noted. (See attached Rolls-Royce engine report). ## Aircraft - Registration: N8393F (not matched to a registry record) - Reported make and model: Hughes 369D - Category: Helicopter - Serial number: 270091D - Engines: Allison 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Public aircraft, Public use - Registered owner: Montana State Dept. of Fish Wildlife & Parks - Airworthiness certificate: Standard, Normal - Departed: BTM, Butte, MT - Destination: BTM, Butte, MT - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 46; injuries: none; commercial; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--no waivers/lim.; last flight review November 16, 2001; seat: left; flight hours: 10,850 total, 1,850 in this make and model, 9,063 as pilot in command ## Weather - Conditions: Instrument (IMC), Day - Wind: 354° at 4 knots - Visibility: 0.75 statute miles - Lowest ceiling: 1,200 ft overcast - Temperature: 30 °F, dew point 28 °F - Altimeter: 29.94 inHg - Observed at: BTM, 5 nm away ## Docket (4 files) The files NTSB released with the investigation on December 19, 2002, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=53985. 9.6 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 344 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40377086&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - FAA Inspector's Statement (item 2, .PDF, 36 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40377090&FileExtension=.PDF&FileName=FAA%20Inspector%27s%20Statement-Redacted.PDF - Passenger Statement (item 3, .PDF, 158 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40377091&FileExtension=.PDF&FileName=Passenger%20Statement-Redacted.PDF - Rolls Royce Engine Teardown Report (item 4, .PDF, 9.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40377094&FileExtension=.PDF&FileName=Rolls%20Royce%20Engine%20Teardown%20Report-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.