# NTSB CEN23LA232: Grumman Acft ENG Cor-Schweizer G-164B, N48485, Bloomfield, NE, June 7, 2023 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: June 7, 2023, 14:00 local (19:00 UTC) - Place: Bloomfield, NE · field - Coordinates: 42.579724, -97.673675 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=42.5797&lon=-97.6737&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Defining event: [Takeoff: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: FAA Flight Standards, Woodward, Inc., Honeywell International -- Powerplant Systems, Hartzell Propeller - NTSB case key (mKey): 192330 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN23LA232 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/192330/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=192330 - Page: https://openairdocs.org/ntsb/CEN23LA232 ## Probable cause A partial loss of engine power during takeoff for reasons that could not be determined. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Power plant](https://openairdocs.org/ntsb-findings/01057100): Aircraft › Aircraft power plant · Unknown/Not determined (probable cause); cases with it: [Grumman Acft ENG Cor-Schweizer G-164B, 2 cases](https://openairdocs.org/ntsb-findings/01057100/cases.md?model=3952802), [All aircraft, 198 cases](https://openairdocs.org/ntsb-findings/01057100/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Takeoff: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) (defining event); cases with it: [Grumman Acft ENG Cor-Schweizer G-164B, 4 cases](https://openairdocs.org/ntsb-events/000/sequence.md?model=3952802), [All aircraft, 1,703 cases](https://openairdocs.org/ntsb-events/000/sequence.md) - [Takeoff: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Grumman Acft ENG Cor-Schweizer G-164B, 21 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=3952802), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The operator reported that the first flight of the day was completed without incident. However, during takeoff for the second flight of the day, the airplane started to lift off the runway but would not climb. The pilot applied full throttle, but the engine did not respond. The airplane went through a fence off the end of the runway and came to rest in a soybean field which resulted in substantial damage to the upper and lower right wings. An engine examination did not reveal any evidence of an uncontained failure or external fire damage. The engine contained multiple indications of power at the time of impact, such as rotational scoring damage by the compressor impellers and turbine blades and earthen material present within the engine. In addition, the torsion shaft was fractured in torsional overload resulting from sudden stoppage due to impact of the propeller. Bench testing determined that the fuel control unit (FCU) cam initially moved axially as the compressor inlet pressure (Pt2) was increased but then stopped moving. Upon disassembly of the fuel control unit, the cam gear was seized in position on the shaft. Metallurgical examination of the camshaft found two depressions on opposite corners of the camshaft slot. The outer camshaft diameter was larger than the specified diameter in the area of the two depressions. The bushing exhibited corresponding areas of wear and distinct gouges along the axis of the bushing and on either side of the shaft slot. One gear tooth on the camshaft exhibited signs of spalling damage and cracking across the entire length of the tooth. The FCU camshaft deformation may have restricted cam translation, which would have reduced metered fuel flow. However, if the camshaft was restricted, the condition would have been present on previous flight(s) since the camshaft translation was a function of altitude changes. It is unlikely that the FCU contributed to the lack of throttle response. A fuel sample taken from the fuel filter bowl consisted of Jet A fuel and water. However, the quantity of water was not consistent with any degradation of engine performance. The investigation was unable to determine the reason for the reduction of engine power during the accident takeoff. ## Factual narrative On June 7, 2023, about 1400 central daylight time, a Grumman G-164B airplane, N48485, was substantially damaged when it was involved in an accident near Bloomfield, Nebraska. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 137 aerial application flight. The operator reported that the first flight of the day was completed without incident. However, during takeoff for the second flight of the day, the airplane started to lift off the runway, but it would not climb. The pilot applied full throttle, but the engine did not respond. The airplane went through a fence off the end of the runway and came to rest in a soybean field. The upper and lower right wings were damaged during the impact sequence. The engine remained secured to the engine mount. The propeller assembly remained attached to the reduction gearbox. Each propeller blade was deformed, and the outboard portion of one blade was separated consistent with the impact sequence. Continuity of the engine controls was confirmed. A fuel sample taken from the fuel filter bowl consisted of Jet A fuel and water. An engine examination did not reveal any evidence of an uncontained failure or external fire damage. The compressor impellers and turbine rotors/blades were intact. Earthen material was observed from the stage 1 compressor impeller through to the combustion chamber. The stage 2 compressor impeller was intact and exhibited localized rotational scoring damage. Stage 1 turbine rotor blade tips exhibited rotational scoring, and the torsion shaft was fractured. Metallurgical examination determined that the torsion shaft fractured due to torsional overload. Bench testing determined that the cam moved axially as the compressor inlet pressure (Pt2) was increased. However, at 11 psia, the cam did not move any further. On disassembly of the fuel control unit, the cam gear was seized in position on the shaft. Metallurgical examination of the camshaft found two depressions on opposite corners of the camshaft slot. Additionally, the outer camshaft diameter was larger than the specified diameter near the two depressions. The bushing exhibited corresponding areas of wear and distinct gouges along the axis of the bushing and on either side of the shaft slot. One gear tooth on the camshaft exhibited signs of spalling damage and cracking across the entire length of the tooth. The propeller governor assembly was intact and undamaged, the input driveshaft rotated freely under hand pressure and the control arm rotated normally. Bench testing of the propeller governor resulted in normal operation. Airplane maintenance records noted that the engine was overhauled in September 1987. The engine logbook did not contain a record of any subsequent engine overhaul. Based on the records, the engine had accumulated about 8,428 hours since overhaul. The engine manufacturer’s time between overhaul (TBO) was either 3,600 hours or 5,400 hours depending on the operator’schosen engine management program. However, compliance with the engine manufacturer’s TBO requirements is not mandated by the Federal Aviation Administration for 14 CFR Part 137 operations. At the time of the accident, the operator reported the airplane weight at 6,830 lbs. The weight and balance data noted an airplane gross weight of 5,500 lbs. However, regulations may permit agricultural operators to establish a maximum weight as an operating limitation for agricultural aircraft. ## Aircraft - Registration: [N48485](https://openairdocs.org/deregistered/N48485-2025-06-13), registration cancelled 2025-06-13, S/N 44B, built 1976 (OpenAirDocs) - Reported make and model: GRUMMAN ACFT ENG COR-SCHWEIZER G-164B - Registry model: [Grumman Acft ENG Cor-Schweizer G-164B](https://openairdocs.org/model/grumman-acft-eng-cor-schweizer-g-164b) (registry code 3952802) (OpenAirDocs) - Registry engine: [Pratt & Whitney R-985 series](https://openairdocs.org/engine/pratt-whitney-r-985-series) (registry code 52008, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 44B - Year built: 1976 - Airframe hours: 8427.8 - Engines: Garrett TPE-331-1-151A 665 horsepower turbo prop - Damage: Substantial damage - Flight: Aerial application, Part 137 - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, May 1, 2023, 12.8 hours before - Departed: 84Y, Bloomfield, NE - Destination: 84Y, Bloomfield, NE - Airport: 84Y, Bloomfield Municipal, runway 14, 2,700 × 50 ft, asphalt - Equipment: Satellite tracking device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 65; injuries: none; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 3, with waivers/limitations; last flight review April 11, 2022; seat: single; restraint: 4-point; flight hours: 14,657 total, 14,657 as pilot in command, 25 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: 60° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: 11,000 ft overcast - Temperature: 90 °F, dew point 57 °F - Altimeter: 29.84 inHg - Observed at: KYKN, 23 nm away - METAR: METAR KYKN 071856Z AUTO 06006KT 10SM SCT080 OVC110 32/14 A2984 ## 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 20230607009899A](https://openairdocs.org/incident/20230607009899A), Jun 7, 2023: Grumman Acft Eng Cor-Schweizer G-164B, Bloomfield, NE, Substantial damage. On Wednesday, June 7, 2023, a pilot was performing aerial application operations in a 1976 Grumman G-164B powered by a Garrett TPE331-1-151A. The part 137… ## Other investigations on N48485 (1) 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. - [NTSB CHI02LA132](https://openairdocs.org/ntsb/CHI02LA132), May 10, 2002: Grumman-Schweizer G-164B (N48485), Hordville, NE, substantial damage. Probable cause: A loss of engine power due to a fractured rocker arm shaf. Contributing to the accident was the soft, furrowed field. ## Docket (11 files) The files NTSB released with the investigation on March 19, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=192330. 377 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 7 pages, 478 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18222230&FileExtension=pdf&FileName=Accident%20Report%20--%20CEN23LA232_redacted-Rel.pdf - Investigation photos (item 2, PDF, 6 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18232364&FileExtension=pdf&FileName=Investigation%20Photos%20--%20CEN23LA232-Rel.pdf - CEN23LA232_powerplant factual report_final (item 3, PDF, 40 pages, 5.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18047778&FileExtension=pdf&FileName=CEN23LA232_Powerplant%20Factual%20Report_FINAL-Rel.pdf - Powerplant factual attachment 1 - Honeywell lab analysis report (item 4, PDF, 17 pages, 3.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18219630&FileExtension=pdf&FileName=Powerplant%20Factual%20Attachment%201%20-%20Honeywell%20Lab%20Analysis%20Report-Rel.pdf - Powerplant factual attachment 2 - component exam test results (item 5, PDF, 11 pages, 16.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18218924&FileExtension=pdf&FileName=Powerplant%20Factual%20Attachment%202%20-%20Component%20Exam%20Test%20Results-Rel.pdf - Powerplants factual - attachment 3 - woodward inca��s final reports (item 6, PDF, 13 pages, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18219790&FileExtension=pdf&FileName=Powerplants%20Factual%20-%20Attachment%203%20-%20Woodward%20Inc%E2%80%99s%20Final%20Reports-Rel.pdf - Materials laboratory factual report (item 7, PDF, 63 pages, 79 photos, 19.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17162793&FileExtension=pdf&FileName=24-022%20-%20Materials%20Lab%20Factual%20Report%20(CEN23LA232)-Rel.pdf - Maintenance records -- airframe (item 8, PDF, 9 pages, 160 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18238672&FileExtension=pdf&FileName=Maintenance%20Records%20--%20Airframe_redacted-Rel.pdf - Maintenance records -- engine (item 9, PDF, 11 pages, 168 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18238166&FileExtension=pdf&FileName=Maintenance%20Records%20--%20Engine_redacted-Rel.pdf - Maintenance records -- weight & balance (item 10, PDF, 1 page, 122 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18228504&FileExtension=pdf&FileName=Maintenance%20Records%20--%20Weight%26Balance_redacted-Rel.pdf - Statement of party representatives to NTSB investigation (item 11, PDF, 3 pages, 919 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18240732&FileExtension=pdf&FileName=Party%20Statements%20--%20CEN23LA232_redacted-Rel.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.