# NTSB CEN11LA646: Bell 206B, N3181J, Spicewood, TX, September 15, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 15, 2011, 09:15 local (14:15 UTC) - Place: Spicewood, TX - Coordinates: 30.477777, -98.121109 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=30.4778&lon=-98.1211&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Low altitude operation/event](https://openairdocs.org/ntsb-events/220) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report April 2, 2012 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Federal Aviation Administration, Rolls-Royce Corporation - NTSB case key (mKey): 81809 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN11LA646 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/81809/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=81809 - Page: https://openairdocs.org/ntsb/CEN11LA646 ## Probable cause The pilot did not maintain adequate rotor rpm during a low-altitude maneuvering flight. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Performance/control parameters: prop/rotor parameters](https://openairdocs.org/ntsb-findings/01062052): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Bell 206B, 11 cases](https://openairdocs.org/ntsb-findings/01062052/cases.md?model=1181511), [All aircraft, 182 cases](https://openairdocs.org/ntsb-findings/01062052/cases.md) - [Personnel issues](https://openairdocs.org/ntsb-findings/02060000): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Bell 206B, 2 cases](https://openairdocs.org/ntsb-findings/02060000/cases.md?model=1181511), [All aircraft, 137 cases](https://openairdocs.org/ntsb-findings/02060000/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: Low altitude operation/event](https://openairdocs.org/ntsb-events/220) (defining event); cases with it: [Bell 206B, 34 cases](https://openairdocs.org/ntsb-events/220/sequence.md?model=1181511), [All aircraft, 780 cases](https://openairdocs.org/ntsb-events/220/sequence.md) - [Autorotation: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Bell 206B, 57 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=1181511), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis While maneuvering the helicopter at an altitude of about 400 feet above ground level, the pilot heard the low rotor aural warning in his headset and observed that the rotor speed gauge was reading about 80 percent and decreasing. He lowered the collective, initiated a left turn, and began an autorotative descent to hilly terrain that contained trees and power lines. During the autorotation, the pilot attempted to avoid the power lines, and the helicopter impacted terrain. Although the pilot reported that he believed the engine lost power, a postaccident examination of the helicopter revealed no evidence of any preimpact mechanical failures or malfunctions. Additionally, the helicopter’s engine was run in a test cell for 1 hour 50 minutes with no anomalies detected. ## Factual narrative On September 15, 2011, at 0915 central daylight time, a Bell 206B single-engine helicopter, N3181J, sustained substantial damage when it impacted terrain while maneuvering near Spicewood, Texas. The private pilot, who was the registered owner, and passenger were not injured. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The local flight departed approximately 0815 from Spicewood Airport (88R), Spicewood, Texas. According to the pilot, he and the passenger departed 88R on a local pleasure flight with approximately 70 gallons of fuel. Approximately 1 hour into the flight and 4 miles southwest of 88R, the pilot reported hearing the low rotor aural warning in his headset and observed the rotor speed gauge to be reading approximately 80 percent and decreasing. At an altitude of approximately 400 feet above ground level, the pilot lowered the collective, initiated a left turn and began an autorotative decent to hilly terrain that contained trees and power lines. During the autorotation, the pilot attempted to avoid the power lines, and the helicopter impacted terrain. Subsequently, the helicopter rolled over and came to rest on its right side. The pilot reported that after the impact, the engine was still operating at an unknown power level, and he used the fuel cutoff to stop the engine. The pilot stated he believed the helicopter experienced an uncommanded reduction in engine power. The pilot reported the wind was calm and the temperature was 86 degrees Fahrenheit. Postaccident examination of the helicopter showed the tail boom had separated and the main rotor blades were bent and twisted. No visual external damage was noted on the Allison 250-C20B engine. The engine was covered in fire suppressant material, which was used by fire rescue for precautionary purposes due to the dry vegetation in the surrounding area. The engine fuel, oil, and pneumatic lines exhibited no visual damage and all connections were secure. The engine was removed and sent to Rolls-Royce Corporation for further examination. A review of the maintenance records revealed the helicopter underwent its most recent annual inspection on February 22, 2011. At the time of accident, the engine had accumulated 14,459 total hours and 107 hours since compressor and turbine section overhaul. On November 8, 2011, the engine was examined by the NTSB and Rolls-Royce Corporation. The N1 drive train remained rotationally free and N2 remained locked. The turbine area was flushed with water and approved alcohol solution at which time fire suppressant material was cleared and N2 became rotationally free. The engine was placed into a test cell for testing in accordance to Rolls-Royce production test specifications. The engine was test run for approximately 1 hour and 50 minutes with no anomalies noted. After the engine run, a Pc system check was performed and no leaks were detected. ## Aircraft - Registration: [N3181J](https://openairdocs.org/deregistered/N3181J-2019-01-30), registration cancelled 2019-01-30, S/N 3771, built 1983 (OpenAirDocs) - Reported make and model: BELL 206B - Registry model: [Bell 206B](https://openairdocs.org/model/bell-206b) (registry code 1181511) (OpenAirDocs) - Registry engine: [Allison 250 SER 250HP](https://openairdocs.org/engine/allison-250-ser-250hp) (registry code 03002, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 3771 - Airframe hours: 20378 - Engines: Allison 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: On File - Registered owner: On File - Airworthiness certificate: Standard, Normal - Last inspection: Annual, February 22, 2011 - Departed: 88R, Spicewood, TX - Destination: 88R, Spicewood, TX ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 74; injuries: minor; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; last flight review November 3, 2009; seat: right; flight hours: 2,852 total, 112 in this make and model, 2,852 as pilot in command, 19 in the last 90 days, 5 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 86 °F, dew point 57 °F - Altimeter: 30.12 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 20110915021979A](https://openairdocs.org/incident/20110915021979A), Sep 15, 2011: Bell 206B, Spicewood, TX, Destroyed. On 09/15/2011 at approximatley 0815 hrs, pilot was on a pleasure flight with one passenger in a Bell 206B helicopter cruising at 105 knots at an altitude of… ## Docket (2 files) The files NTSB released with the investigation on February 17, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=81809. 1.2 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 935 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40362668&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Excerpt of Rolls-Royce Engine Report (item 2, .PDF, 263 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40362669&FileExtension=.PDF&FileName=Excerpt%20of%20Rolls-Royce%20Engine%20Report-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.