# NTSB ERA09LA460: Mcdonnell Douglas Helicopter 369E, N527BB, Acworth, GA, August 12, 2009 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: August 12, 2009, 10:00 local (14:00 UTC) - Place: Acworth, GA - Coordinates: 34.066112, -84.676666 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.0661&lon=-84.6767&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-descent: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: Serious injuries - Injuries: 1 serious, 1 minor - Status: Completed, report March 16, 2011 - Report: Approved by Office Director - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO - NTSB case key (mKey): 74516 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA09LA460 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74516/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74516 - Page: https://openairdocs.org/ntsb/ERA09LA460 ## Probable cause The loss of engine power due to the fatigue failure of the third-stage turbine wheel airfoil. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (turbine/turboprop): turbine section](https://openairdocs.org/ntsb-findings/01057250): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Mcdonnell Douglas Helicopter 369E, 3 cases](https://openairdocs.org/ntsb-findings/01057250/cases.md?model=3027369), [All aircraft, 74 cases](https://openairdocs.org/ntsb-findings/01057250/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-descent: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Mcdonnell Douglas Helicopter 369E, 5 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=3027369), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Mcdonnell Douglas Helicopter 369E, 6 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=3027369), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Autorotation: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Mcdonnell Douglas Helicopter 369E, 9 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=3027369), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot stated that he and an observer were conducting an aerial observation when during the descent he heard a loud noise. Subsequently, he received an "ENG OUT" audio and caution lights, and made an emergency autorotation into a field. An examination of the engine’s turbine section revealed rub marks throughout the turbine section consistent with an out-of-balance condition caused by a third-stage turbine airfoil release. The third-stage wheel airfoil fractured in fatigue near the root of the airfoil and no anomalies were found at the fatigue origin. The fracture surface of the failed third-stage blade revealed high-cycle fatigue failure over an extended period of time. The crack propagation is estimated to be greater than 2000 cycles. No additional cracks were found on the other third-stage wheel airfoils. Review of the logbook revealed that the airframe engine total time was 3,820 hours and the engine had gone through a 100- and 300-hour inspection at 3,809.6 engine hours. All airworthiness directives and applicable service bulletins as well as all instructions for continued airworthiness were complied with. The hot section and turbine inspection was completed on February 21, 2008, at 2,958 hours. The third-stage turbine wheel was overhauled on February 3, 2004, at 1210.6 hours and 1633.0 cycles and was due to be replaced at 4,710.6 hours. At the time of the accident the wheel had 2609.7 hours and 2412.0 cycles. ## Factual narrative On August 12, 2009, about 1000 eastern daylight time, a McDonnell-Douglas 369E, N527BB, lost engine power during a descent and landed hard during an autorotation landing in Acworth, Georgia. The commercial rated pilot received minor injuries, and the passenger was seriously injured. The helicopter was substantially damaged by impact forces. The flight was operated as an aerial observation flight under the provisions of 14 Code of Federal Regulations Part 91, and no flight plan was filed. Visual meteorological conditions prevailed at the time of the accident. The pilot stated that he and an observer were conducting an aerial observation of power lines. He climbed to 1,400 feet mean sea level, and was awaiting clearance from McCollum Field, Georgia (RYY) to enter its airspace. After receiving the clearance to enter RYY, he began a descent. Approximately 5 to 10 seconds into the descent he heard a "'bang and braking" noise. Subsequently, he received an "ENG OUT" audio and caution lights. He then made an emergency autorotation into a field. Examination of the helicopter by a Federal Aviation Administration inspector revealed that the helicopter collided with a runoff ditch behind residential homes. Examination of the airframe and flight control system components revealed no evidence of preimpact mechanical malfunction. The helicopter was recovered from the ditch and an examination was conducted on the engine. Examination of the engine revealed no evidence of impact damage or fire, and all engine mounts were intact. The gas producer fuel control lever operated, and the power turbine governor control lever traveled freely, and after the engine was removed from the airframe both control levers operated fully. All fuel, lube and pneumatic lines, coupling nuts and B-nuts were checked for security and were found tight and marked with torque paint. Inspection of the inlet plenum chamber did not reveal any evidence of foreign material or missing hardware. Inspection of the compressor inlet showed no signs of erosion or foreign object damage. The compressor rotated freely by hand. The accessory gearbox was undamaged, and both gear trains turned freely and smoothly by hand. Drive train continuity was confirmed throughout. Examination of the turbine section revealed rub marks throughout the turbine section consistent with an out-of-balance condition caused by a third stage turbine airfoil release. The third stage wheel airfoil fractured in fatigue near the root of the airfoil, progressing approximately 0.55 inch from the trailing edge prior to the final separation in overload. No anomalies were found at the fatigue origin. Damage observed on the other turbine components was consistent with secondary damage after the third stage airfoil separation. The microstructure, hardness, and chemistry of the third stage turbine wheel met the engineering drawing requirements. The fracture surface of the failed third stage blade revealed high cycle fatigue failure of anextended period of time. The crack propagation is estimated to be greater than 2000 cycles. No additional cracks were found on the other third stage wheel airfoils. Review of the logbook pages revealed that the airframe total time was 4,257 hours, and the engine total time was 3,820 hours. The airframe and the engine had gone through a 100 and 300 hour inspection at 4,246.6 airframe hours and 3,809.6 engine hours. All airworthiness directives and applicable service bulletins as well as all instructions for continued airworthiness were complied with. The hot section and turbine inspection was completed on February 21, 2008 at 2,958 hours. The number 3 turbine wheel power turbine was overhauled on February 3, 2004 at 1210.6 hours and 1633.0 cycles, and was due to be replaced at 4,710.6 hours. The number 3 turbine wheel had 2609.7 hours and 2412.0 cycles at the time of the accident. The number 3 turbine wheel had 1940.0 hours remaining and 3588.0 cycles remaining at the time of the accident. ## Aircraft - Registration: [N527BB](https://openairdocs.org/deregistered/N527BB-2013-02-20), registration cancelled 2013-02-20, S/N 0329E, built 1989 (OpenAirDocs) - Reported make and model: MCDONNELL DOUGLAS HELICOPTER 369E - Registry model: [Mcdonnell Douglas Helicopter 369E](https://openairdocs.org/model/mcdonnell-douglas-helicopter-369e) (registry code 3027369) (OpenAirDocs) - Registry engine: [Allison 250-C20 series](https://openairdocs.org/engine/allison-250-c20-series) (registry code 03020, turbo-prop) (OpenAirDocs) - Category: Helicopter - Serial number: 0329E - Airframe hours: 4257 - Engines: ALLISON 250-C20 SER 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial observation, Part 91 - Operator: Rotorworks LLC - Registered owner: Rotorworks LLC - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, August 1, 2009, 10 hours before - Departed: RYY, Acworth, GA - Destination: RYY, Acworth, GA ## Weather - Conditions: Visual (VMC), Day - Wind: 330° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: 11,000 ft broken - Temperature: 81 °F, dew point 70 °F - Altimeter: 30.03 inHg - Observed at: RYY, 5 nm away ## 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 20090812048179A](https://openairdocs.org/incident/20090812048179A), Aug 12, 2009: Mcdonnell D 369E, Acworth, GA, Substantial damage. On August 12, 2009 at approximately 10:15 (LCL), Mcdonnell Douglas helicopter N527BB experienced a loss of power and was forced to make an emergency landing in… ## Docket (8 files) The files NTSB released with the investigation on November 23, 2010, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74516. 4.2 MB in all. - Other Pertinent Forms and Reports-Engine Logbook Page (item 1, .PDF, 99 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40328966&FileExtension=.PDF&FileName=Other%20Pertinent%20Forms%20and%20Reports-Engine%20Logbook%20Page-Redacted.PDF - Other Pertinent Forms and Reports-Engine Logbook Page Turbine Overhaul (item 2, .PDF, 329 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40328967&FileExtension=.PDF&FileName=Other%20Pertinent%20Forms%20and%20Reports-Engine%20Logbook%20Page%20Turbine%20Overhaul-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 3, .PDF, 232 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40329096&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF - Photo 1-Main Wreckage-FAA digital (item 4, .PDF, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40329100&FileExtension=.PDF&FileName=Photo%201-Main%20Wreckage-FAA%20digital-Master.PDF - Other Pertinent Forms and Reports-Rolls Royce Overhaul Limits (item 5, .PDF, 11 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40330215&FileExtension=.PDF&FileName=Other%20Pertinent%20Forms%20and%20Reports-Rolls%20Royce%20Overhaul%20Limits-Redacted.PDF - Other Pertinent Forms and Reports-NTSB Report Supplement Helicopter Ops Info (item 6, .PDF, 77 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40330641&FileExtension=.PDF&FileName=Other%20Pertinent%20Forms%20and%20Reports-NTSB%20Report%20Supplement%20Helicopter%20Ops%20Info-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 7, .PDF, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40330709&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Other Pertinent Forms and Reports-Inspector teardown report (item 8, .PDF, 25 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40337983&FileExtension=.PDF&FileName=Other%20Pertinent%20Forms%20and%20Reports-Inspector%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.