# NTSB ERA19LA238: Aero Commander S2R, N5680X, Cuthbert, GA, July 25, 2019 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: July 25, 2019, 19:25 local (23:25 UTC) - Place: Cuthbert, GA - Coordinates: 31.604999, -84.824996 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=31.6050&lon=-84.8250&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Eastern Region Aviation - Parties: Transportation Safety Board of Canada, Pratt & Whitney Engine Services, FAA - ATL FSDO - NTSB case key (mKey): 99964 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA19LA238 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/99964/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=99964 - Page: https://openairdocs.org/ntsb/ERA19LA238 ## Probable cause The failure of the No. 1 bearing due to fatigue which resulted in a partial loss of engine power. The reason for the bearing failure could not be determined based on the available information. ## 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 · Fatigue/wear/corrosion (probable cause); cases with it: [Aero Commander S2R, 1 case](https://openairdocs.org/ntsb-findings/01057230/cases.md?model=0143022), [All aircraft, 53 cases](https://openairdocs.org/ntsb-findings/01057230/cases.md) - [Engine (turbine/turboprop): compressor section](https://openairdocs.org/ntsb-findings/01057230): Aircraft › Aircraft power plant · Unknown/Not determined (probable cause); cases with it: [Aero Commander S2R, 1 case](https://openairdocs.org/ntsb-findings/01057230/cases.md?model=0143022), [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 (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Aero Commander S2R, 4 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=0143022), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Aero Commander S2R, 3 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=0143022), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The pilot reported that, about 5 minutes after takeoff, at an altitude about 500 ft above ground level, the engine lost partial power. The pilot performed a forced landing to a field, during which the airplane sustained substantial damage. Examination of the engine revealed that the compressor front support (No. 1) bearing had failed, resulting in compressor rotor misalignment. The rotor misalignment resulted in severe impeller-to-shroud rub, including wear-through in several locations, flow disruption, and the engine power loss. The reason for the bearing failure could not be determined based on the available information. ## Factual narrative On July 25, 2019, about 1925 eastern daylight time, an Aero Commander S2R, N5680X, was substantially damaged when it was involved in an accident near Cuthbert, Georgia. The commercial pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. The pilot performed a preflight inspection of the airplane at 0700 with no anomalies noted. He departed on the 14th flight of the day and set the engine power at 50 lbs of torque producing 96% gas generator speed (NG). About 5 minutes into the flight, at 500 ft above ground level, he recalled a loss of airspeed with the sound of the engine winding down. He stated the oil pressure was still in the green arc and the NG had reduced to 35%. He performed a forced landing to a field, during which the airplane sustained substantial damage. Review of the maintenance logbooks revealed that the engine was installed on the accident airplane in 2013 and operated 2,189 hours until an unscheduled removal for a compressor problem in December 2015. The repair involved a vibration workscope and included replacement of both the Nos. 1 and 2 (compressor support) bearings. The engine was reinstalled and was operated 2,287 hours before the accident. Examination of the engine revealed that the gas generator system did not turn when rotated at the starter drive pad. The accessory gearbox magnetic chip detector was not shipped with the engine, but heavy ferrous and non-ferrous debris was captured when the accessory gearbox oil was drained through filter paper. Fragments identified as tangs from the No. 1 bearing internal key washer were identified in the debris. The gas generator rotor remained seized after the accessory gearbox was removed from the engine. The accessory gearbox drivetrain could be rotated when the coupling shaft was turned with force. Scoring damage was noted in the main pressure pump, pressure relief valve and housing, and other oil-wetted components, consistent with hard debris circulating in the oil. An approximate 120° arc of material was missing from the forward edge of the No. 1 bearing retention nut cup washer. The missing section included one of the two retention (stake) features. Oil was observed on bearing surfaces and there was no evidence of distress from lack of lubrication. The No. 1 bearing cage was fractured into four sections. All 10 ball elements were present and showed local material transfer. The thrust inner ring ball path was heavily worn. The non-thrust inner ring ball path was worn to a lesser extent. The No. 1 bearing outer ring and the internal key washer were in place inside the compressor bearing adapter; but the 17 internal key washer tangs were separated. There were oval impressions in the ball path, including deep imprints in five consecutive locations. The stationary rear air seal was locally gouged. The No. 1 bearing oil jet was undamaged. A flow bench check found its spray pattern acceptable. Metallurgicalexamination of the bearing by the engine manufacturer found evidence of fatigue on two bearing cage fracture surfaces at the pocket rounded edge; however, the extensive secondary damage prevented further evaluation. The cage microstructure was consistent with the drawing specification, and hardness measurements conformed to the drawing requirements. No material anomalies were noted. Energy dispersive x-ray spectroscopy spot analyses found no concentrations of nickel to suggest that key washer or cup washer material had migrated into the bearing and initiated the failure. Manufacturer records showed that the No. 1 bearing was sold new as a spare in 1985. It was installed in the accident engine during the December 2015 compressor repair. According to the repair shop, it had undergone inspection and been determined serviceable after removal from an engine that was disassembled for spares. ## Aircraft - Registration: [N5680X](https://openairdocs.org/aircraft/N5680X), registered now, S/N 1880R, built 1974 (OpenAirDocs) - Reported make and model: AERO COMMANDER S2R - Registry model: [Aero Commander S2R](https://openairdocs.org/model/aero-commander-s2r) (registry code 0143022) (OpenAirDocs) - Registry engine: [Pratt & Whitney R1340 series](https://openairdocs.org/engine/pratt-whitney-r1340-series) (registry code 52016, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 1880R - Year built: 1974 - Engines: Pratt & Whitney PT6A-34 750 horsepower turbo prop - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Precision Aerial LLC, doing business as AG Operations - Registered owner: Precision Aerial LLC - Airworthiness certificate: Special, Restricted (Special) - Departed: 25J, Cuthbert, GA - Destination: 25J, Cuthbert, GA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 33; injuries: none; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review December 14, 2017; seat: center; restraint: 4-point; flight hours: 7,496 total, 6,934 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 81 °F, dew point 64 °F - Altimeter: 30.04 inHg - Observed at: KBIJ, 13 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 20190725024189A](https://openairdocs.org/incident/20190725024189A), Jul 25, 2019: Aero Commander S2R, Cuthbert, GA, Substantial damage. Less than 5 min into 137 flt, 6 mi enroute to dusting op approx. 10 mi se of K25J, pilot noticed strong oil smell and 1/2 normal ng and dropping for config.… ## Docket (4 files) The files NTSB released with the investigation on February 25, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=99964. 6.8 MB in all. - NTSB 6120 (item 1, PDF, 11 pages, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11953571&FileExtension=pdf&FileName=NTSB%206120%20ERA19LA238_Redacted-Rel.pdf - Pilot interview (item 2, PDF, 1 page, 180 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11970865&FileExtension=pdf&FileName=Memorandum%20for%20Record-Pilot%20Interview-Rel.pdf - Powerplants group chairman's factual report (item 3, PDF, 11 pages, 17 photos, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11710854&FileExtension=pdf&FileName=ERA19LA238%20Powerplants%20Factual%20Report-Rel.pdf - Investigative photograghs (item 4, PDF, 3 pages, 2.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11952923&FileExtension=pdf&FileName=Memorandum%20for%20Record-Investigative%20Photographs-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.