# NTSB CEN22LA228: Air Tractor AT-602, N5007R, Allport, AR, June 1, 2022

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Class 3 · Limited · Final report
- Date: June 1, 2022, 17:00 local (22:00 UTC)
- Place: Allport, AR · Field to the east of a private airstrip.
- Coordinates: 34.543405, -91.799332 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=34.5434&lon=-91.7993&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Defining event: [Enroute: Fuel contamination](https://openairdocs.org/ntsb-events/193)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Central Region
- Parties: FAA Little Rock FSDO, Air Tractor, Transportation Safety Board of Canada, Hartzell Propeller, Pratt & Whitney Canada
- NTSB case key (mKey): 105190
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN22LA228
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/105190/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=105190
- Page: https://openairdocs.org/ntsb/CEN22LA228

## Probable cause

A partial loss of engine power due to fuel contamination from foreign object debris. Contributing to the accident was the operator’s failure to follow the manufacturer’s required airframe fuel filter inspection interval.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Engine (turbine/turboprop)](https://openairdocs.org/ntsb-findings/01057200): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Air Tractor AT-602, 3 cases](https://openairdocs.org/ntsb-findings/01057200/cases.md?model=0390309), [All aircraft, 67 cases](https://openairdocs.org/ntsb-findings/01057200/cases.md)
- [Fluids: fuel](https://openairdocs.org/ntsb-findings/01071010): Aircraft › Fluids/misc hardware · Fluid condition (probable cause); cases with it: [Air Tractor AT-602, 8 cases](https://openairdocs.org/ntsb-findings/01071010/cases.md?model=0390309), [All aircraft, 1,695 cases](https://openairdocs.org/ntsb-findings/01071010/cases.md)
- [Inspection: scheduled/routine inspection](https://openairdocs.org/ntsb-findings/02061520): Personnel issues › Task performance · Owner/builder (probable cause); cases with it: [Air Tractor AT-602, 1 case](https://openairdocs.org/ntsb-findings/02061520/cases.md?model=0390309), [All aircraft, 167 cases](https://openairdocs.org/ntsb-findings/02061520/cases.md)
- [Inspection: scheduled/routine inspection](https://openairdocs.org/ntsb-findings/02061520): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Air Tractor AT-602, 1 case](https://openairdocs.org/ntsb-findings/02061520/cases.md?model=0390309), [All aircraft, 167 cases](https://openairdocs.org/ntsb-findings/02061520/cases.md)
- [Oversight: oversight of maintenance](https://openairdocs.org/ntsb-findings/04032020): Organizational issues › Support/oversight/monitoring · Operator (probable cause); cases with it: [Air Tractor AT-602, 1 case](https://openairdocs.org/ntsb-findings/04032020/cases.md?model=0390309), [All aircraft, 28 cases](https://openairdocs.org/ntsb-findings/04032020/cases.md)
- [Fuel system: fuel filter-strainer](https://openairdocs.org/ntsb-findings/01022821): Aircraft › Aircraft systems · Not serviced/maintained (probable cause); cases with it: [Air Tractor AT-602, 1 case](https://openairdocs.org/ntsb-findings/01022821/cases.md?model=0390309), [All aircraft, 52 cases](https://openairdocs.org/ntsb-findings/01022821/cases.md)
- [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Air Tractor AT-602, 13 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=0390309), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md)
- [Object/animal/substance: debris/dirt/foreign object](https://openairdocs.org/ntsb-findings/03022055): Environmental issues › Physical environment · Effect on equipment (probable cause); cases with it: [Air Tractor AT-602, 1 case](https://openairdocs.org/ntsb-findings/03022055/cases.md?model=0390309), [All aircraft, 101 cases](https://openairdocs.org/ntsb-findings/03022055/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Prior to flight: Aircraft maintenance event](https://openairdocs.org/ntsb-events/040); cases with it: [Air Tractor AT-602, 2 cases](https://openairdocs.org/ntsb-events/040/sequence.md?model=0390309), [All aircraft, 484 cases](https://openairdocs.org/ntsb-events/040/sequence.md)
- [Enroute: Fuel contamination](https://openairdocs.org/ntsb-events/193) (defining event); cases with it: [Air Tractor AT-602, 3 cases](https://openairdocs.org/ntsb-events/193/sequence.md?model=0390309), [All aircraft, 225 cases](https://openairdocs.org/ntsb-events/193/sequence.md)
- [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Air Tractor AT-602, 13 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=0390309), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md)
- [Landing: Nose over/nose down](https://openairdocs.org/ntsb-events/096); cases with it: [Air Tractor AT-602, 8 cases](https://openairdocs.org/ntsb-events/096/sequence.md?model=0390309), [All aircraft, 2,287 cases](https://openairdocs.org/ntsb-events/096/sequence.md)
- [Post-impact: Evacuation](https://openairdocs.org/ntsb-events/460); cases with it: [Air Tractor AT-602, 1 case](https://openairdocs.org/ntsb-events/460/sequence.md?model=0390309), [All aircraft, 103 cases](https://openairdocs.org/ntsb-events/460/sequence.md)

## Analysis

The aerial application airplane was loaded with chemical for application on a rice field. Immediately after the takeoff from the private airstrip, the pilot heard a “loud pop” noise from the turboprop engine, and he observed flames emit from the left side of the airplane. During the forced landing, the pilot reported that it felt like there was a “slight recovery” of engine power, but then the engine ceased producing power. During the forced landing, the airplane nosed over and came to rest inverted, resulting in substantial damage to the left wing, the fuselage, and the empennage. Examination of the airframe revealed foreign object debris (FOD) between the airframe fuel filter pleats and in the fuel filter bowl. Examination of the engine revealed contamination of the engine fuel filter and various fuel wetted accessories. The engine exhibited rotational contact signatures on the compressor turbine and the power turbine components consistent with the engine producing power at the time of impact; however, the engine power output at the time of impact could not be determined. Marks on the piston, cylinder, and blade damage indicated the propeller was operating at low blade angles with low or no power at impact. Chemical testing of the FOD samples from the airframe and the engine revealed a composition consistent with an unknown fertilizer-type material. A review of the airplane’s maintenance records revealed that the airplane was flown about 44 hours past the manufacturer’s required fuel filter inspection interval. It is likely that contaminated fuel obstructed the engine fuel filter and was injected into the engine, which resulted in a partial loss of engine power. The source of the FOD and how it entered the fuel tanks could not be determined based on the available information. It is possible that, had the operator completed the airframe fuel filter inspection within the required interval, the contamination of the filter may have been identified.

## Factual narrative

On June 1, 2022, about 1700 central daylight time, an Air Tractor AT-602 airplane, N5007R, sustained substantial damage when it was involved in an accident near Allport, Arkansas. The pilot sustained minor injury. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. The pilot reported he was on the 35th flight of the day and the airplane had been performing well all day with no issues noted. The airplane was refueled two flights before the accident flight and at the time of the accident each wing fuel tank was about half full of Jet A fuel. The airplane’s 6,500 lb hopper was loaded with 3,600 lbs of urea. For the accident flight, the pilot intended to fly to a rice field to apply fertilizer. Immediately after the takeoff from the private airstrip, the pilot heard a “loud pop” noise emit from the turboprop engine and he observed flames emit from the left side of the airplane. The pilot confirmed that a loss of engine power occurred, he made sure the flaps were down, and he began to scan the area to perform a forced landing. During the forced landing, the pilot reported that it felt like there was a “slight recovery” of engine power, but then the engine ceased producing power. The pilot retarded the throttle and landed on a flat field consisting of grass, dirt, and mud. During the landing, the airplane nosed over and came to rest inverted. The pilot was able to egress from the airplane without further incident. The airplane sustained substantial damage to the left wing, the fuselage, and the empennage. Examination of the airframe established flight control continuity. Fuel was found in the fuel lines at the fuel pump, to the fuel selector, the header tank, and forward to the airframe fuel filter. The airframe fuel filter assembly on the firewall was removed and FOD of unknown origin was found between the airframe fuel filter pleats and in the fuel filter bowl. Examination of the engine revealed FOD contamination of the engine fuel filter and various fuel-wetted accessories. Bench testing of the fuel control unit, the flow divider/dump valve, and fuel nozzles indicated that they performed within expected parameters. The engine exhibited rotational contact signatures on the compressor turbine and power turbine components consistent with the engine producing power at the time of impact. The engine power output at the time of impact could not be determined. Examination of the propeller revealed no mechanical malfunctions or failures that would have prevented normal operation. Marks on the piston, cylinder, and blade damage indicated that the propeller was operating at low blade angles with low or no power at impact. Chemical testing of the FOD samples from the engine and the airframe revealed a composition consistent with an unknown, fertilizer-type material. A review of the airplane’s maintenance records revealed that the airframe fuel filter was most recently inspected and cleaned on August 12,2021, at 1,285.5 hours Hobbs time. The accident occurred at 1,429.5 hours Hobbs time. The Air Tractor AT-602 Maintenance Manual stated that the airframe fuel filter was to be inspected and cleaned every 100 hours. Engine maintenance was performed on May 23, 2022, and the engine was successfully test run, but the associated maintenance logbook entry did not show any tasks related to the fuel system. The maintenance manual discussed cleaning the airframe fuel filter and provided a caution that stated , “if any contamination is found in either fuel filter, investigate the cause and rectify the problem.” The operator was unable to provide fuel or chemical loading records. The operator additionally reported that after the accident, the other Air Tractor AT-602 airplane that they operate did not have any mechanical issues and that both airplanes received fuel from the same fuel truck. Air Tractor published Service Letter #148, Fuel Contamination, on June 24, 1996. This document discusses fuel contamination with Air Tractor airplanes and states in part: As we all know, it is of the utmost importance to maintain a clean fuel system in your aircraft. It is also just as important to acquire clean fuel and maintain clean storage facilities. The National Agricultural Aviation Association published a Fly Safe Message, “Avoid Engine Fuel System Contamination,” on May 1, 2023. This document discusses preventing engine fuel system contamination for aerial application aircraft and states in part: Ag aircraft are subject to numerous situations that could result in contamination to the engine fuel system such as unclean fuel storage facilities, aircraft washing, loading, refueling, and maintenance; and/or operating/storing the aircraft outside in condensation/rain. Contamination could be from a variety of sources such as chemicals, debris from the aircraft and maintenance work, or dirt, dust, microbial growth, rust, sand, and water. Contamination of an engine fuel system could result in either a partial or a complete loss of engine power. Turbine engine components that could be adversely affected by contamination include the fuel control unit and the fuel nozzles. According to Federal Aviation Administration Advisory Circular 20-43, turbine engine fuel controls and pumps are more sensitive than piston engine fuel systems. Their fuel feed and pumping systems must work harder, tolerances are closer and fuel pressures are higher. Fine contaminates may block fuel supply systems and erode critical parts of engine and fuel control systems. Due to the nature of aerial application work, operators should consider increasing the inspection frequency of turbine engine fuel system components. Always follow the maintenance manual when performing your work. Consult with the airframe, the engine, and the engine accessory manufacturers on any additional service documents regarding the topic of fuel contamination.

## Aircraft

- Registration: [N5007R](https://openairdocs.org/deregistered/N5007R-2023-04-19), registration cancelled 2023-04-19, S/N 602-0501, built 1998 (OpenAirDocs)
- Reported make and model: AIR TRACTOR INC AT-602 (NO SERIES)
- Registry model: [Air Tractor AT-602](https://openairdocs.org/model/air-tractor-at-602) (registry code 0390309) (OpenAirDocs)
- Registry engine: [Pratt & Whitney Canada PT6A-66 series](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-66-series) (registry code 52118, turbo-prop) (OpenAirDocs)
- Category: Airplane
- Serial number: 602-0501
- Year built: 1998
- Airframe hours: 1429.5
- Engines: P&W Canada PT6A-60AG 1020 horsepower turbo prop
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Operator: Webb Flying Service Inc, doing business as Webb Flying Service Inc
- Registered owner: Webb Flying Service Inc
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: 100 hour, August 12, 2021, 144 hours before
- Airport: None, Private, runway 092, 2,000 × 21 ft, concrete
- Equipment: Data recorder, Stall warning system

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 56; injuries: minor; commercial; airplane ratings: single-engine land; medical: class 2, with waivers/limitations; last flight review February 1, 2022; seat: single; restraint: 4-point; flight hours: 13,511 total, 7,035 in this make and model, 13,511 as pilot in command, 100 in the last 90 days, 30 in the last 30 days, 10 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 220° at 8 knots
- Visibility: 10 statute miles
- Temperature: 91 °F, dew point 72 °F
- Altimeter: 29.90 inHg
- Observed at: KSGT, 12 nm away
- METAR: KSGT 012156Z AUTO 22008KT 10SM FEW048 33/22 A2990 RMK AO2 LTG DSNT NW SLP124 T03280222

## 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 20220601003389A](https://openairdocs.org/incident/20220601003389A), Jun 1, 2022: Air Tractor Inc AT-602, Allport, AR, Substantial damage. At approximatelly 1715 CST on 1 June, 2022, N5007R, loaded with 3600 pounds of urea fertilizer, was taking off eastbound from a private strip near Allport…

## Docket (18 files)

The files NTSB released with the investigation on March 20, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=105190. 80.4 MB in all.

- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 7 pages, 2.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16637794&FileExtension=pdf&FileName=NTSB%20Form%206120_1_Redacted-Rel.pdf
- Accident photographs (item 2, PDF, 20 pages, 7.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16637296&FileExtension=pdf&FileName=Accident%20Photographs-Rel.pdf
- Various statements (item 3, PDF, 5 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16693193&FileExtension=pdf&FileName=Various%20Statements_Redacted-Rel.pdf
- NTSB - airframe examination report (item 4, PDF, 7 pages, 168 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16649226&FileExtension=pdf&FileName=CEN22LA228%20NTSB%20Examination%20Report-Rel.pdf
- Hartzell propeller - propeller examination report (item 5, PDF, 24 pages, 6.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16693961&FileExtension=pdf&FileName=CEN22LA228%20Propeller%20Exam%20Report%20No.%20220601_Redacted-Rel.pdf
- Pratt & whitney Canada - engine examination report (item 6, PDF, 54 pages, 10.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16633435&FileExtension=pdf&FileName=PWC%20Engine%20Examination%20Report%20Redacted-Rel.pdf
- Airframe fuel pump and fuel pump motor examination reports (item 7, PDF, 2 pages, 534 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16637408&FileExtension=pdf&FileName=Airframe%20Fuel%20Pump%20and%20Fuel%20Pump%20Motor%20Examination%20Reports_Redacted-Rel.pdf
- Airframe maintenance records 2018 to accident (item 8, PDF, 12 pages, 22.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16648805&FileExtension=pdf&FileName=Airframe%20Maintenance%20Records%202018%20to%20Accident_Redacted-Rel.pdf
- Engine maintenance records 2018 to accident (item 9, PDF, 7 pages, 10.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16648815&FileExtension=pdf&FileName=Engine%20Maintenance%20Records%202018%20to%20Accident_Redacted-Rel.pdf
- Most recent maintenance work order - r.t. turbines, inc. (item 10, PDF, 2 pages, 3.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16692497&FileExtension=pdf&FileName=Most%20Recent%20Work%20Order_Redacted-Rel.pdf
- Air tractor AT-602 airplane flight manual excerpt (item 11, PDF, 1 page, 218 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16637306&FileExtension=pdf&FileName=Air%20Tractor%20AT-602%20Airplane%20Flight%20Manual%20Excerpt-Rel.pdf
- Air tractor AT-602 maintenance manual excerpts (item 12, PDF, 4 pages, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16634168&FileExtension=pdf&FileName=Air%20Tractor%20AT-602%20Maintenance%20Manual%20Excerpts-Rel.pdf
- Air tractor service letters and national agricultural aviation association fly safe message (item 13, PDF, 9 pages, 746 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16633078&FileExtension=pdf&FileName=Air%20Tractor%20Service%20Letters%20and%20National%20Agricultural%20Aviation%20Association%20Fly%20Safe%20Message-Rel.pdf
- Electronic devices - specialist factual report (item 14, PDF, 13 pages, 2.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15768152&FileExtension=pdf&FileName=CEN22LA228%20Electronic%20Devices%20-%20Specialist%27s%20Factual%20Report-Rel.pdf
- Electronic devices - specialist factual report - attachment 1 (item 15, CSV, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15767931&FileExtension=csv&FileName=Electronic%20Devices%20-%20Specialist%20Factual%20Report%20-%20Attachment%201-Rel.csv
- Restraint system photographs (item 16, PDF, 10 pages, 5.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16637027&FileExtension=pdf&FileName=Restraint%20Sytem%20Photographs-Rel.pdf
- NTSB wreckage release form (item 17, PDF, 1 page, 3.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16637266&FileExtension=pdf&FileName=NTSB%20Wreckage%20Release%20Form_Redacted-Rel.pdf
- NTSB party member forms - air tractor and hartzell propeller (item 18, PDF, 2 pages, 525 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16633615&FileExtension=pdf&FileName=NTSB%20Party%20Member%20Forms%20-%20Air%20Tractor%20and%20Hartzell%20Propeller%20Redacted-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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