# NTSB WPR11CA101: Bell 206B3, N78BR, Three Forks, MT, January 15, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Data collection · Final report - Date: January 15, 2011, 13:00 local (20:00 UTC) - Place: Three Forks, MT - Coordinates: 45.875, -111.573333 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.8750&lon=-111.5733&mi=10 - Phase of flight: [Emergency descent](https://openairdocs.org/ntsb-phases/600) (OpenAirDocs' grouping) - Defining event: [Autorotation: Hard landing](https://openairdocs.org/ntsb-events/092) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report May 26, 2011 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: FAA FSDO - NTSB case key (mKey): 78171 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR11CA101 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/78171/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=78171 - Page: https://openairdocs.org/ntsb/WPR11CA101 ## Probable cause The pilot’s inadequate use of throttle during the practice autorotation that resulted in a hard landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine controls: power lever](https://openairdocs.org/ntsb-findings/01057603): Aircraft › Aircraft power plant · Incorrect use/operation (probable cause); cases with it: [Bell 206B, 2 cases](https://openairdocs.org/ntsb-findings/01057603/cases.md?model=1181511), [All aircraft, 95 cases](https://openairdocs.org/ntsb-findings/01057603/cases.md) - [Use of equip/info: use of equip/system](https://openairdocs.org/ntsb-findings/02063015): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Bell 206B, 5 cases](https://openairdocs.org/ntsb-findings/02063015/cases.md?model=1181511), [All aircraft, 1,391 cases](https://openairdocs.org/ntsb-findings/02063015/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Autorotation: Hard landing](https://openairdocs.org/ntsb-events/092) (defining event); cases with it: [Bell 206B, 28 cases](https://openairdocs.org/ntsb-events/092/sequence.md?model=1181511), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) ## Analysis The pilot practiced several maneuvers and then entered a straight-in practice autorotation. He pointed the helicopter into the wind at 800 feet above ground level near midfield and above the runway. He reduced the throttle to flight idle and lowered the collective while gently flaring the nose of the helicopter to set up the appropriate main rotor rpm and airspeed. He reported that he monitored those parameters carefully during the descent and noted that they remained well within the normal range. At the bottom of the descent, the pilot flared a little high to allow a margin of safety for tail boom clearance as he was planning a power recovery from the autorotation. The pilot stated that he did not add power at that point and that there was inadequate rotor inertia to dampen the landing, even though he applied full collective deflection. The helicopter hit hard and sustained substantial damage. The aft portion of the tail boom and tail rotor separated due to a main rotor blade contact and the skids were damaged. ## Factual narrative The pilot practiced several maneuvers, and then entered a straight-in practice autorotation. He pointed the helicopter into the wind at 800 feet above ground level (agl) near midfield and above the runway. He rolled the throttle to flight idle, and lowered the collective while gently flaring the nose of the helicopter to set up the appropriate main rotor revolutions per minute (rpm) and airspeed. He monitored those parameters carefully during the descent, and noted that they remained well within the normal range. At the bottom of the descent, the pilot flared a little high to allow a margin of safety for tail boom clearance as he was planning a power recovery from the autorotation. However, the pilot stated that he did not add power at that point, and there was inadequate rotor inertia to dampen the landing, even though he applied full collective deflection. The helicopter hit hard, and sustained substantial damage. The aft portion of the tail boom and tail rotor separated due to a main rotor blade contact, and the skids were damaged. The pilot performed an emergency shut down; he closed the throttle, and switched off the battery, generator, and fuel valve. After exiting the helicopter he secured the battery. ## Aircraft - Registration: [N78BR](https://openairdocs.org/aircraft/N78BR), registered now, S/N 4001, built 1988 (OpenAirDocs) - Reported make and model: BELL 206B3 - Registry model: [Bell 206B](https://openairdocs.org/model/bell-206b) (registry code 1181511) (OpenAirDocs) - Registry engine: [Rolls-Royce 250-C20J](https://openairdocs.org/engine/rolls-royce-250-c20j) (registry code 54181, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 4001 - Airframe hours: 2701 - Engines: Rolls-Royce Allison 250-C20J 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Skymission LLC - Registered owner: Skymission LLC - Airworthiness certificate: Standard, Normal - Last inspection: Annual, June 23, 2010 - Departed: BZN, Bozeman, MT - Destination: BZN, Bozeman, MT - Airport: 9S5, Three Forks, runway 02, 5,100 × 60 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 57; injuries: none; private; medical: class 3, with waivers/limitations; last flight review April 11, 2009; seat: right; flight hours: 692 total, 674 in this make and model, 607 as pilot in command, 26 in the last 90 days, 4 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 310° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 41 °F, dew point 27 °F - Altimeter: 30.11 inHg - Observed at: KBZN ## 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 20110115001329A](https://openairdocs.org/incident/20110115001329A), Jan 15, 2011: Bell 206B, Three Forks, MT, Substantial damage. On January 15th, 2011, at about 1320 mountain standard time, a Bell 206B, N78BR, was substantially damaged following a practice power-recovery autorotation at… ## Docket (1 files) The files NTSB released with the investigation on February 17, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=78171. 2.8 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 2.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40343027&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-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.