# NTSB CEN17LA309: Air Tractor AT-802A, N528MB, Galesburg, IL, August 9, 2017

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Class 3 · Limited · Final report
- Date: August 9, 2017, 07:30 local (12:30 UTC)
- Place: Galesburg, IL
- Coordinates: 40.973056, -90.303611
- Nearby events: https://openairdocs.org/map.md?lat=40.9731&lon=-90.3036&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Defining event: [Maneuvering-low-alt flying: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Central Region
- Parties: Federal Aviation Administration, Springfield FSDO, Transportation Safety Board of Canada, Pratt & Whitney Canada
- NTSB case key (mKey): 95787
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN17LA309
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/95787/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=95787
- Page: https://openairdocs.org/ntsb/CEN17LA309

## Probable cause

A total loss of engine power due to the fracture of a single 1st stage compressor rotor airfoil in high-cycle fatigue as a result of the erosion and thinning of the airfoil's leading edge. Contributing to the fractured airfoil and loss of engine power was the operator’s decision to operate the engine past the manufacturer’s recommended time between overhaul.

## 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: [Air Tractor AT-802A, 1 case](https://openairdocs.org/ntsb-findings/01057230/cases.md?model=0390308), [All aircraft, 53 cases](https://openairdocs.org/ntsb-findings/01057230/cases.md)
- [Info processing/decision: decision making/judgment](https://openairdocs.org/ntsb-findings/02041520): Personnel issues › Action/decision · Owner/builder; cases with it: [Air Tractor AT-802A, 11 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md?model=0390308), [All aircraft, 3,098 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md)
- [Maintenance/inspections: time limits](https://openairdocs.org/ntsb-findings/01010510): Aircraft › Aircraft handling/service · Not inspected; cases with it: [Air Tractor AT-802A, 1 case](https://openairdocs.org/ntsb-findings/01010510/cases.md?model=0390308), [All aircraft, 17 cases](https://openairdocs.org/ntsb-findings/01010510/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: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Air Tractor AT-802A, 7 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=0390308), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md)
- [Landing: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Air Tractor AT-802A, 6 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=0390308), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md)
- [Landing: Loss of control on ground](https://openairdocs.org/ntsb-events/230); cases with it: [Air Tractor AT-802A, 9 cases](https://openairdocs.org/ntsb-events/230/sequence.md?model=0390308), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md)
- [Landing: Landing gear collapse](https://openairdocs.org/ntsb-events/094); cases with it: [Air Tractor AT-802A, 1 case](https://openairdocs.org/ntsb-events/094/sequence.md?model=0390308), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md)

## Analysis

The pilot was on an agricultural flight when the engine lost total power. The pilot completed a forced landing in a nearby field, but he was unable to maintain directional control of the airplane after it landed in the dense soybean crop. The outboard portion of the right wing and aileron were substantially damaged during the forced landing. A postaccident engine examination revealed that a single 1st stage compressor rotor airfoil had fractured near its root. The fatigue crack originated from a thinned leading edge due to significant erosion at the bottom of the airfoil pressure side; however, the exact location of the fatigue origin could not be determined because it had been obliterated by the erosion. The observed fracture features were consistent with a crack that had progressed in highcycle fatigue. Dimensional measurements of the fractured airfoil and the two adjacent airfoils revealed that they were under the minimum requirement for an airfoil. The airfoils also exhibited evidence of fine wear scratches, characteristic of fine abrasive particles impacting the airfoil, and thinning of their leading edges. The underlying cause of the airfoil erosion could not be determined with certainty; however, based on the observed damage, it was possibly the result of environmental conditions. The engine had accumulated 4,349.3 hours since new and had never been overhauled. The engine manufacturer’s recommended time between overhaul (TBO) was 3,000 hours; however, the operator was not required to comply with the recommended TBO interval under current regulations due to the type of operation.

## Factual narrative

On August 9, 2017, about 0730 central daylight time, an Air Tractor AT-802A airplane, N528MB, was substantially damaged when it was involved in an accident near Galesburg, Illinois. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 137 agricultural flight. The pilot reported that the accident occurred about 1 hour into his first aerial-application flight of the day. He stated that he felt a slight "thud or bump" that he initially believed was the airplane flying through its own propeller wash during a turn. The pilot stated that the engine gauges were indicating normal parameters as he continued to line-up for another spray pass; however, before his next spray pass the engine experienced a similar "thud" that he identified as a compressor stall. The pilot entered a climb to gain safe altitude and maneuvered the airplane away from nearby homes. The engine experienced several more compressor stalls and the pilot saw sparks departing the engine exhaust ducts before it experienced a total loss of power. The pilot completed a forced landing in a nearby field, during which the airplane ground looped in the dense soybean crop. The landing gear collapsed, and the outboard portion of the right wing and aileron were substantially damaged during the forced landing. Examination of the engine revealed that a single 1st stage compressor rotor airfoil had fractured near the root. The fatigue crack originated from a thinned leading edge due to significant erosion at the bottom of the airfoil pressure side; however, the exact location of the fatigue origin could not be determined due to erosion damage. The observed fracture features were consistent with a crack that had progressed in high-cycle fatigue. Dimensional measurements of the fractured airfoil and the two adjacent airfoils revealed that they were up to 0.050 inch less than the minimum requirement for an airfoil. The airfoils also exhibited evidence of fine wear scratches, characteristic of fine abrasive particles impacting the airfoil, and thinning of the leading edge of the airfoils. The remaining damage observed through the remaining gas path was considered secondary to the separation of the single 1st stage compressor rotor airfoil. According to maintenance documentation, the engine had accumulated 4,349.3 hours since new, and 1,808.6 hours since being partially disassembled for inspection and repair on December 16, 2013; however, according to the logbook entry, the gas generator was not inspected at that time. The most recent inspection of the gas generator was completed during an annual/100-hour inspection completed on May 1, 2017, about 99.3 hours before the accident. Based on the available maintenance documentation, the engine had not been overhauled during its service history. The engine manufacturer recommends that the engine be overhauled after 3,000 hours. Federal Aviation Administration regulations do not require Part 137 operators tocomply with an engine manufacturer's recommended time between overhaul interval provided the engine meets annual and 100-hour requirements.

## Aircraft

- Registration: [N528MB](https://openairdocs.org/aircraft/N528MB), registered now, S/N 802A-0350 (OpenAirDocs)
- Reported make and model: AIR TRACTOR AT-802A
- Registry model: [Air Tractor AT-802A](https://openairdocs.org/model/air-tractor-at-802a) (registry code 0390308) (OpenAirDocs)
- Registry engine: [Pratt & Whitney Canada PT6A-67AG](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-67ag) (registry code 52211, turbo-prop) (OpenAirDocs)
- Category: Airplane
- Serial number: 802A-0350
- Year built: 2010
- Airframe hours: 4349.3
- Engines: Pratt & Whitney Canada PT6A-67AG 1350 horsepower turbo prop
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Operator: Lesco Aviation Inc.
- Registered owner: Lesco Aviation Inc.
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, May 1, 2017, 99.3 hours before
- Departed: C66, Monmouth, IL
- Equipment: Stall warning system, Handheld GPS

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 36; injuries: none; commercial; airplane ratings: single-engine sea, single-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review January 14, 2017; seat: center; restraint: 5-point; flight hours: 10,000 total, 6,000 in this make and model, 450 in the last 90 days, 150 in the last 30 days, 0 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 61 °F, dew point 61 °F
- Altimeter: 30.21 inHg
- Observed at: GBG, 6 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 20170809012859A](https://openairdocs.org/incident/20170809012859A), Aug 9, 2017: Air Tractor Inc AT-802A, Galesburg, IL, Substantial damage. On August 9, 2017, about 0730 central daylight time, an Air tractor AT-802A, N528MB, sustained substantial damage during a forced landing near Galesburg,…

## Docket (8 files)

The files NTSB released with the investigation on February 18, 2021, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=95787. 10.4 MB in all.

- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 419 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11674483&FileExtension=pdf&FileName=01%20-%20Pilot%20Report_Redacted-Rel.pdf
- Memorandum of conversation (item 2, PDF, 1 page, 44 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11675151&FileExtension=pdf&FileName=02%20-%20Memorandum%20of%20Conversation%20(Claude%20H%20Gooch)-Rel.pdf
- Engine examination report (item 3, PDF, 38 pages, 4.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11675541&FileExtension=pdf&FileName=03%20-%20Engine%20Examination%20Report_Public-Rel.pdf
- Airframe logbook (item 4, PDF, 19 pages, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11675161&FileExtension=pdf&FileName=06%20-%20Airframe%20Logbook_Redacted-Rel.pdf
- Engine gas generator logbook (item 5, PDF, 20 pages, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11675551&FileExtension=pdf&FileName=07%20-%20Engine%20Gas%20Generator%20Logbook_Redacted-Rel.pdf
- Engine power section logbook (item 6, PDF, 4 pages, 312 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11675478&FileExtension=pdf&FileName=08%20-%20Engine%20Power%20Section%20Logbook_Redacted-Rel.pdf
- Weather (item 7, PDF, 1 page, 62 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11675631&FileExtension=pdf&FileName=09%20-%20Weather-Rel.pdf
- Photos (item 8, PDF, 2 pages, 557 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11675872&FileExtension=pdf&FileName=10%20-%20Photos-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.

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