# NTSB CEN24LA193: Air Tractor AT-502, N15189, Covert, KS, May 19, 2024 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: May 18, 2024, 19:30 local (May 19, 2024, 00:30 UTC) - Place: Covert, KS - Coordinates: 39.234419, -98.701146 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.2344&lon=-98.7011&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: No injuries - Injuries: 1 uninjured - Status: Completed, report May 13, 2026 - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: Pratt & Whitney Canada, Transportation Safety Board of Canada, FAA-FSDO, Air Tractor, Inc - NTSB case key (mKey): 194284 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN24LA193 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194284/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=194284 - Page: https://openairdocs.org/ntsb/CEN24LA193 ## Probable cause The improper maintenance of the fuel control unit, which resulted in air leakage and a loss of control of fuel flow to the engine. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine fuel and control: fuel controlling system](https://openairdocs.org/ntsb-findings/01057320): Aircraft › Aircraft power plant · Malfunction (probable cause); cases with it: [Air Tractor AT-502, 1 case](https://openairdocs.org/ntsb-findings/01057320/cases.md?model=0390303), [All aircraft, 59 cases](https://openairdocs.org/ntsb-findings/01057320/cases.md) - [Engine fuel and control: fuel controlling system](https://openairdocs.org/ntsb-findings/01057320): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Air Tractor AT-502, 1 case](https://openairdocs.org/ntsb-findings/01057320/cases.md?model=0390303), [All aircraft, 59 cases](https://openairdocs.org/ntsb-findings/01057320/cases.md) - [Maintenance](https://openairdocs.org/ntsb-findings/02062000): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Air Tractor AT-502, 2 cases](https://openairdocs.org/ntsb-findings/02062000/cases.md?model=0390303), [All aircraft, 143 cases](https://openairdocs.org/ntsb-findings/02062000/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: [Air Tractor AT-502, 1 case](https://openairdocs.org/ntsb-events/340/sequence.md?model=0390303), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Maneuvering-low-alt flying: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Air Tractor AT-502, 7 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=0390303), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Landing-landing roll: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Air Tractor AT-502, 17 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=0390303), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis During an agricultural application flight, the pilot noticed a loss of thrust and adjusted engine power as needed. The subsequent application pass was normal; however, while turning the airplane around for another pass, he felt the “tail drop” and noticed that several engine gauges had exceeded limitations. The pilot attempted to reduce engine power but found that the engine was unresponsive to power control inputs and that the airplane was unable to maintain altitude. He chose to land on a nearby gravel road, during which the airplane impacted tree branches and ground looped into a ditch, resulting in substantial damage to both wings. After the airplane came to rest, the engine continued to run until the pilot cut off the fuel supply. Postaccident examination of the engine revealed an improperly torqued and safety wired P3 adapter on the fuel control unit (FCU). This allowed the two attachment screws, used to secure the P3 adapter to the main body of the FCU, to back off, which resulted in excessive air leakage and movement of the gasket between the adapter and the FCU main body. This leakage fluctuated when light finger pressure was applied to the P3 adapter that connected to the FCU main body. The P3 adapter’s seal with the FCU’s main body likely degraded over time because the screws backed off, allowing relative motion between the gasket and sealing surfaces. The intermittent air leakage compromised FCU fuel control capability, likely resulting in the FCU’s fuel flow metering valve to move to its minimum setpoint and the erratic engine behavior observed by the pilot. The date that the accident FCU was installed on the accident engine could not be determined based on maintenance records. The only entry indicating this FCU’s condition was on August 25, 2022, and noted that the FCU was already installed on the engine when received and was in serviceable condition during final inspection. The only maintenance performed on this FCU while installed on the accident airplane was changing the fuel filter. ## Factual narrative On May 18, 2024, about 1930 central daylight time, an Air Tractor AT-502 airplane, N15189, was substantially damaged when it was involved in an accident near Covert, Kansas. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 agricultural flight. The pilot stated that, after arriving at the field and performing one application pass, he noticed a loss of thrust and adjusted engine power as needed. The second pass was normal; however, while turning around to perform the third pass, the airplane was “super sluggish.” He felt the “tail drop” and noticed that the engine torque, NG (gas generator speed), and propeller rpm gauges were all “over redline.” The interstage turbine temperature (ITT) gauge indicated high but had not exceeded redline. The pilot stated that the engine was unresponsive to power control inputs, and with he airplane unable to maintain altitude, he chose to land on a nearby gravel road. The pilot stated that he attempted to extend the wing flaps, but the flaps did not extend. During the landing, the airplane impacted tree branches and ground looped into a ditch, which resulted in substantial damage to both wings. The engine continued to run after the airplane came to rest until the pilot shut off the fuel supply. Postaccident examination of the airframe revealed no anomalies with the flap system. The system was functionally tested and operated as designed. The throttle, condition, and propeller lever flex cables were examined for the full length with no anomalies found; however, the start control and propeller levers were observed to be stiff, with the start control stuck in place. All three cables were tested for slide and breakaway force using a force gauge. The testing revealed that the start control and propeller control flex cables were found to be exceeding the design maximum force limit. A label was found on the propeller lever flex cable that showed a manufacture date of June 29, 2017. Examination of the engine revealed an improperly torqued and safety wired P3 adapter on the fuel control unit (FCU). The FCU (with flexible P3 air supply line) was removed from the engine and tested for external air leakage in accordance with manufacturer test specifications, which stated that only “slow bubbling” was allowed from specific FCU locations, including the joint between the drive body and P3 air adapter. The testing was performed twice and found to be 15 and 36 inches of mercury, both outside of limits. The FCU was subsequently removed from the test stand and disassembled. The P3 adapter attached to the FCU’s main body was loose and appeared to move with light finger pressure. Two screws securing the P3 adapter to the FCU’s main body were safety wired; however, the wire on both screws appeared to be in a neutral configuration. A digital screwdriver registered zero torque to unscrew one screw, while the other was removed by hand without the screwdriver. Both screws and theirthreaded holes appeared in good condition. Contact surfaces on the P3 adapter, aluminum gasket, and FCU main body appeared fretted. A light scratch was found between the Py restrictor and aft screw hole on the FCU main body. The P3 air adapter displayed small, metallic particles inside the Px air cavity (see figure 1). Figure 1. Fretted aluminum gasket (left) and FCU main body (right) The flexible P3 supply line appeared undamaged and clear of internal obstructions. The P3 line connects to a pressure port fitting on the P3 adapter and has a conical metering orifice to convert incoming P3 air into Px air. This orifice exhibited a concentric impression around the cone portion of the fitting. Multiple engine logbook entries had incorrect or missing engine operational hours and/or cycles. The date that the accident FCU was installed on the accident engine could not be determined based on maintenance records; however, according to the engine and airplane logbooks, the accident airplane flew with the accident FCU for at least 448.2 hours and 167 cycles with no reported engine anomalies. The only entry indicating this FCU’s condition was for maintenance completed on August 25, 2022. The entry noted that the FCU was already installed on the engine when received and was in serviceable condition during final inspection. The only maintenance performed on this FCU while installed on the accident airplane was changing the fuel filter. ## Aircraft - Registration: [N15189](https://openairdocs.org/aircraft/N15189), registered now, S/N 502-0155, built 1991 (OpenAirDocs) - Reported make and model: AIR TRACTOR INC AT-502 - Registry model: [Air Tractor AT-502](https://openairdocs.org/model/air-tractor-at-502) (registry code 0390303) (OpenAirDocs) - Registry engine: [Pratt & Whitney PT6A series](https://openairdocs.org/engine/pratt-whitney-pt6a-series) (registry code 52032, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 502-0155 - Year built: 1991 - Airframe hours: 8514.1 - Engines: Pratt & Whitney Canada PT6A-34A 750 horsepower turbo prop - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Tri Rotor Spray & Chemical - Registered owner: Tri Rotor Spray & Chemical - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, January 1, 2024 - Departed: K75, Osborne, KS - Equipment: ADS-B, Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 24; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review March 9, 2023; seat: single; restraint: 5-point; flight hours: 1,782 total, 950 in this make and model, 1,717 as pilot in command, 189 in the last 90 days, 130 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 40° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 79 °F, dew point 52 °F - Altimeter: 29.89 inHg - Observed at: KRSL, 22 nm away - METAR: KRSL 190053Z AUTO 04009KT 10SM CLR 26/11 A2989 RMK AO2 SLP108 T02560111 ## 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 20240518009869A](https://openairdocs.org/incident/20240518009869A), May 18, 2024: Air Tractor Inc AT-502, Osborne, KS, Substantial damage. On 05/18/2024 at approximately 8:15 pm CDT, a single engine AT-502 aircraft sustained substantial damage after landing eastbound on a rural road approximately… ## Docket (9 files) The files NTSB released with the investigation on May 13, 2026, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=194284. 71.5 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 10 pages, 41.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20073784&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Pilot's statement mor (item 2, PDF, 1 page, 114 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20101225&FileExtension=pdf&FileName=MOR%20-%20Pilot-Rel.pdf - Airframe logbook excerpts (item 3, PDF, 8 pages, 7.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20073302&FileExtension=pdf&FileName=Airframe%20Logbook_Redacted-Rel.pdf - Engine logbook (item 4, PDF, 30 pages, 4.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20100765&FileExtension=pdf&FileName=Engine%20Logbook_Redacted-Rel.pdf - Photo array (item 5, PDF, 2 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20073585&FileExtension=pdf&FileName=Photo%20Arrary-Rel.pdf - Examination summary (item 6, PDF, 5 pages, 181 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20073904&FileExtension=pdf&FileName=Examination%20Summary-Rel.pdf - Powerplants group chairman's factual report (item 7, PDF, 36 pages, 4.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19020503&FileExtension=pdf&FileName=Powerplants%20Group%20Factual%20Report%20CEN24LA193-Rel.pdf - Powerplants attachment 1 vse aviation investigation report (item 8, PDF, 21 pages, 8.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19020703&FileExtension=pdf&FileName=VSE%20FCU%20Investigation%20Report%201%20Redacted-Rel.pdf - Powerplants attachment 2 vse aviation investigation report (item 9, PDF, 15 pages, 3.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19021338&FileExtension=pdf&FileName=VSE%20FCU%20Investigation%20Report%202%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. --- 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.