# NTSB CEN11LA370: Bell 47G-3B-1, N96SH, Lakeville, MN, May 25, 2011 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: May 25, 2011, 11:40 local (16:40 UTC) - Place: Lakeville, MN - Coordinates: 44.669681, -93.23941 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=44.6697&lon=-93.2394&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed, report November 7, 2012 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 79306 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN11LA370 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/79306/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=79306 - Page: https://openairdocs.org/ntsb/CEN11LA370 ## Probable cause The loss of engine power due to a loose B-nut on the compressor discharge pressure bleed line. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine bleed air system](https://openairdocs.org/ntsb-findings/01057500): Aircraft › Aircraft power plant · Not specified (probable cause); cases with it: [Bell 47G-3B-1, 1 case](https://openairdocs.org/ntsb-findings/01057500/cases.md?model=1181028), [All aircraft, 7 cases](https://openairdocs.org/ntsb-findings/01057500/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: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Bell 47G-3B-1, 2 cases](https://openairdocs.org/ntsb-events/340/sequence.md?model=1181028), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Maneuvering-low-alt flying: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341); cases with it: [Bell 47G-3B-1, 5 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=1181028), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Autorotation: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341); cases with it: [Bell 47G-3B-1, 5 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=1181028), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Landing-flare/touchdown: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Bell 47G-3B-1, 10 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=1181028), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot stated that the helicopter experienced a total loss of engine power while maneuvering during an aerial application operation. He performed a forced landing to a swamp, which resulted in substantial damage to the airframe. Examination of the engine revealed that the compressor discharge pressure bleed line between the governor and the fuel control was leaking at a loose B-nut. ## Factual narrative On May 25, 2011, about 1140 central daylight time, a Bell 47G-3B-1, N96SH, experienced a total loss of engine power while maneuvering near Lakeville, Minnesota. The pilot subsequently made a forced landing on a swamp near Lakeville, Minnesota. The certificated commercial pilot sustained serious injuries. The helicopter sustained substantial damage to the fuselage and tailboom when it impacted terrain during the forced landing. The helicopter was registered to and operated by Scotts Helicopter Services Inc under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed and no flight plan had been filed for the flight that originated from Flying Cloud Airport (FCM), Minneapolis, Minnesota. Examination of the engine (Rolls Royce Allison T63A700, serial number AE-400951) by a Federal Aviation Administration inspector from the Minneapolis Flight Standards District Office revealed that the Pc bleed line (from the governor to the fuel control) was leaking at the B-nut, which had come loose. The inspector stated that the operator had a spare engine at it facilities and that engine had torque lines painted onto the engine's fittings. The accident engine did not have torque lines painted onto its fittings. The inspector stated that there is no requirement to use torque lines and that the new engine maintenance manuals now discuss the use of torque lines. The time since the engine's last inspection was 59.4 hours. ## Aircraft - Registration: [N96SH](https://openairdocs.org/aircraft/N96SH), registered now, S/N 2927, built 1964 (OpenAirDocs) - Reported make and model: BELL 47G-3B-1 - Registry model: [Bell 47G-3B-1](https://openairdocs.org/model/bell-47g-3b-1) (registry code 118103A) (OpenAirDocs) - Registry engine: [Allison 250-C10D](https://openairdocs.org/engine/allison-250-c10d) (registry code 03035, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 2927 - Airframe hours: 13752 - Engines: Allison T63A700 317 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Scotts Helicopter Services Inc - Registered owner: Scotts Helicopter Services Inc - Airworthiness certificate: Special, Restricted (Special); Standard, Normal - Last inspection: Annual, March 22, 2011 - Departed: FCM, Minneapolis, MN - Destination: Lakeville, MN ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 34; injuries: minor; commercial, flight instructor; medical: class 2, without waivers/limitations; last flight review March 10, 2011; seat: left; flight hours: 2,565 total, 464 in this make and model, 2,499 as pilot in command, 82 in the last 90 days, 56 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 70° at 10 knots - Visibility: 10 statute miles - Observed at: LVN, 5 nm away ## Docket (2 files) The files NTSB released with the investigation on September 12, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=79306. 756 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 704 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40371503&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Record of Conversation (item 2, .PDF, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40371505&FileExtension=.PDF&FileName=Record%20of%20Conversation-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.