# NTSB CEN12IA096: Bell Helicopter Textron Canada 407, N435PH, Gulf Of Mexico, December 1, 2011 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: December 1, 2011, 10:05 local (16:05 UTC) - Place: Gulf Of Mexico - Coordinates: 28.424722, -92.875 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=28.4247&lon=-92.8750&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report April 10, 2013 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Rolls Royce, PHI, Inc., Federal Aviation Administration - NTSB case key (mKey): 82447 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN12IA096 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/82447/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=82447 - Page: https://openairdocs.org/ntsb/CEN12IA096 ## Probable cause The failure of the compressor section No. 2 bearing due to false brinnelling and fatigue. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (turbine/turboprop): compressor section](https://openairdocs.org/ntsb-findings/01057230): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Bell Helicopter Textron Canada 407, 1 case](https://openairdocs.org/ntsb-findings/01057230/cases.md?model=1182154), [All aircraft, 53 cases](https://openairdocs.org/ntsb-findings/01057230/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Bell Helicopter Textron Canada 407, 2 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=1182154), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) ## Analysis While maneuvering for a precautionary landing to an oil rig platform because of a chip light indication, the helicopter's engine lost power. The pilot entered an autorotation, called mayday, inflated the helicopter’s floats, and performed a successful water landing. The pilot and passenger were able to exit the helicopter unassisted into a life raft and were picked up within 10 minutes. Examination and disassembly of the engine revealed the No. 2 bearing had failed. Metallurgical examination of the bearing showed the No. 2 bearing outer ring cracked in fatigue due to false brinnelling, which occurs in cases where the bearing is stationary but is subjected to ambient vibration or shock during transport. A spalling area was severe enough to propagate mechanical stress in the outer ring causing the ring to fracture. The engine compressor section was overhauled 2.7 hours before the failure. ## Factual narrative On December 1, 2011, about 1005 central standard time, a Bell 407 helicopter, N435PH, was successfully autorotated to the water following a loss of engine power while maneuvering near a platform in the Gulf of Mexico. The helicopter was not damaged during the on water landing. The commercial pilot, and sole passenger, were not injured. The helicopter was registered to and operated by PHI, Inc., under the provisions of 14 Code of Federal Regulations Part 135 as a non-scheduled air-taxi flight. Visual meteorological conditions prevailed and a company flight plan had been filed. The flight originated from platform EC278-C, and was en route to platform EC261, both in the Gulf Of Mexico. According to the pilot, while en route to EC261 the engine chip light illuminated. The flight was abeam platform EC278-B at the time, and the pilot elected to divert for a precautionary landing. While on the base leg to EC278-B, the pilot heard a loud whining noise, followed by a loud popping noise, and the helicopter began to yaw. The pilot entered an autorotation, called mayday, inflated the floats, and performed a successful water landing. The pilot and passenger were able to exit the helicopter unassisted into a life raft and were picked up within 10 minutes. The helicopter remained upright for approximately 20 minutes before overturning. The engine was removed from the helicopter and examined at the PHI facility in Lafayette, Louisiana, under the supervision of a Federal Aviation Administration inspector. Examination and disassembly of the engine revealed the No. 2 bearing was fractured. The bearing components were located throughout the engine and retained for metallurgical examination. According to the operator's maintenance records, the Rolls-Royce Model 250-C74B gas turbine engine, serial number CAE 847428, underwent a 150/300 hour inspection, and an overhaul to the compressor section, at a total time of 7,475.6 hours. The engine was installed on the helicopter 2.7 hours prior to the accident. Metallurgical examination of the bearing and other components was completed by Rolls-Royce Corporation, Indianapolis, Indiana. According to Rolls-Royce, the No. 2 bearing outer ring cracked in fatigue, initiating from a spalled area on the raceway surface. The microstructure, hardness, and chemistry of the outer ring conformed to the engineering drawing requirements. The damage associated with the other compressor and turbine components examined was consistent with damage that would occur after the No. 2 bearing failure. The failed bearing was then sent to FAG Aerospace, Inc, Stratford, Ontario, Canada, for evaluation. Results of the evaluation showed the failure occurred due to false brinnelling, where the bearing is stationary, but subjected to ambient vibration or shock during transport. The bearing balls were free to vibrate within the bearing. During the vibration period, the bearing experienced relative microscopic motion. The spacing between each set ofbrinnelling marks was equal to the ball spacing within the bearing. False brinnelling increased sufficient load during bearing operation which caused premature spalling. One spalling area was severe enough to propagate mechanical stress in the outer ring causing the ring to fracture. ## Aircraft - Registration: [N435PH](https://openairdocs.org/deregistered/N435PH-2014-01-09), registration cancelled 2014-01-09, S/N 53891, built 2008 (OpenAirDocs) - Reported make and model: BELL HELICOPTER TEXTRON CANADA 407 - Registry model: [Bell Helicopter Textron Canada 407](https://openairdocs.org/model/bell-helicopter-textron-canada-407) (registry code 1182154) (OpenAirDocs) - Registry engine: [Rolls-Royce 250-C47B](https://openairdocs.org/engine/rolls-royce-250-c47b) (registry code 54585, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 53891 - Airframe hours: 4769 - Engines: ROLLS-ROYC 250-C47B 813 horsepower turbo shaft - Damage: No damage - Flight: Part 135 - Operator: Phi Inc - Registered owner: Phi Inc - Airworthiness certificate: Standard, Normal - Last inspection: AAIP, November 29, 2011, 2.7 hours before - Departed: EC-278C, GM - Destination: EC-261, GM - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 32; injuries: none; commercial; instrument ratings: helicopter; medical: class 1, without waivers/limitations; last flight review March 27, 2011; seat: right; flight hours: 3,848 total, 849 in this make and model, 3,834 as pilot in command, 238 in the last 90 days, 52 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 130° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 70 °F, dew point 52 °F - Altimeter: 30.21 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). - [Incident 20111201029769I](https://openairdocs.org/incident/20111201029769I), Dec 1, 2011: Bell Helicopter Textron Canada 407, Intercoastal Ci, LA, No damage. Helicopter took off from gulf of Mexico oil platform EC278-C enroute to EC261. The engine chip detector light illuminated followed by a loud whining noise… ## Docket (5 files) The files NTSB released with the investigation on February 25, 2013, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=82447. 6.5 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 483 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40387672&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Excerpt of Rolls Royce Report (item 2, .PDF, 4.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40387673&FileExtension=.PDF&FileName=Excerpt%20of%20Rolls%20Royce%20Report%0D%0A-Master.PDF - PHI Engine Teardown Report (item 3, .PDF, 104 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40387674&FileExtension=.PDF&FileName=PHI%20Engine%20Teardown%20Report-Master.PDF - PHI Engine Status Report (item 4, .PDF, 99 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40387676&FileExtension=.PDF&FileName=PHI%20Engine%20Status%20Report-Master.PDF - FAG Metallurgical Report (item 5, .PDF, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40387677&FileExtension=.PDF&FileName=FAG%20Metallurgical%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.