# NTSB CEN24LA318: Ayres S2R, N4004K, Stanwood, MI, June 20, 2024

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Class 3 · Limited · Final report
- Date: June 20, 2024, 07:06 local (11:06 UTC)
- Place: Stanwood, MI · Open grass field near Stanwood, Michigan.
- Coordinates: 43.581438, -85.362503 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=43.5814&lon=-85.3625&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Defining event: [Maneuvering-low-alt flying: Low altitude operation/event](https://openairdocs.org/ntsb-events/220)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Central Region
- Parties: FAA Grand Rapids FSDO
- NTSB case key (mKey): 194940
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN24LA318
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194940/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=194940
- Page: https://openairdocs.org/ntsb/CEN24LA318

## Probable cause

The pilot’s failure to maintain terrain clearance during a low-level aerial application flight, which resulted in impact with terrain and a subsequent forced landing. Contributing to the accident was the location of the spray boom pressure gauge, which required the pilot to divert his attention away from the airplane’s flight path, and the operator’s decision to locate the spray boom pressure gauge outside of the cockpit.

## Findings

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

- [Equipment/furnishings: agricultural/external load sys](https://openairdocs.org/ntsb-findings/01022551): Aircraft › Aircraft systems · Design (probable cause); cases with it: [Ayres S2R-600, 1 case](https://openairdocs.org/ntsb-findings/01022551/cases.md?model=0970102), [All aircraft, 14 cases](https://openairdocs.org/ntsb-findings/01022551/cases.md)
- [Attention/monitoring: monitoring equip/instruments](https://openairdocs.org/ntsb-findings/02021525): Personnel issues › Psychological · Pilot (probable cause); cases with it: [Ayres S2R-600, 1 case](https://openairdocs.org/ntsb-findings/02021525/cases.md?model=0970102), [All aircraft, 142 cases](https://openairdocs.org/ntsb-findings/02021525/cases.md)
- [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Ayres S2R-600, 1 case](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=0970102), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md)
- [Attention/monitoring: monitoring environment](https://openairdocs.org/ntsb-findings/02021545): Personnel issues › Psychological · Pilot (probable cause); cases with it: [Ayres S2R-600, 2 cases](https://openairdocs.org/ntsb-findings/02021545/cases.md?model=0970102), [All aircraft, 809 cases](https://openairdocs.org/ntsb-findings/02021545/cases.md)
- [Design: equipment design](https://openairdocs.org/ntsb-findings/04011010): Organizational issues › Development · Operator (probable cause); cases with it: [Ayres S2R-600, 1 case](https://openairdocs.org/ntsb-findings/04011010/cases.md?model=0970102), [All aircraft, 35 cases](https://openairdocs.org/ntsb-findings/04011010/cases.md)
- [Performance/control parameters: altitude](https://openairdocs.org/ntsb-findings/01062012): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Ayres S2R-600, 2 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md?model=0970102), [All aircraft, 1,310 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md)
- [Indicating/recording systems](https://openairdocs.org/ntsb-findings/01023100): Aircraft › Aircraft systems · Design (probable cause); cases with it: [Ayres S2R-600, 1 case](https://openairdocs.org/ntsb-findings/01023100/cases.md?model=0970102), [All aircraft, 18 cases](https://openairdocs.org/ntsb-findings/01023100/cases.md)
- [Attention/monitoring: task monitoring/vigilance](https://openairdocs.org/ntsb-findings/02021520): Personnel issues › Psychological · Pilot (probable cause); cases with it: [Ayres S2R-600, 1 case](https://openairdocs.org/ntsb-findings/02021520/cases.md?model=0970102), [All aircraft, 330 cases](https://openairdocs.org/ntsb-findings/02021520/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: Miscellaneous/other](https://openairdocs.org/ntsb-events/900); cases with it: [Ayres S2R-600, 1 case](https://openairdocs.org/ntsb-events/900/sequence.md?model=0970102), [All aircraft, 1,556 cases](https://openairdocs.org/ntsb-events/900/sequence.md)
- [Maneuvering-low-alt flying: Low altitude operation/event](https://openairdocs.org/ntsb-events/220) (defining event); cases with it: [Ayres S2R-600, 2 cases](https://openairdocs.org/ntsb-events/220/sequence.md?model=0970102), [All aircraft, 780 cases](https://openairdocs.org/ntsb-events/220/sequence.md)
- [Maneuvering-low-alt flying: Attempted remediation/recovery](https://openairdocs.org/ntsb-events/060); cases with it: [Ayres S2R-600, 1 case](https://openairdocs.org/ntsb-events/060/sequence.md?model=0970102), [All aircraft, 1,422 cases](https://openairdocs.org/ntsb-events/060/sequence.md)
- [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Ayres S2R-600, 2 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=0970102), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md)
- [Landing: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490); cases with it: [Ayres S2R-600, 1 case](https://openairdocs.org/ntsb-events/490/sequence.md?model=0970102), [All aircraft, 1,309 cases](https://openairdocs.org/ntsb-events/490/sequence.md)
- [Post-impact: Evacuation](https://openairdocs.org/ntsb-events/460); cases with it: [Ayres S2R-600, 1 case](https://openairdocs.org/ntsb-events/460/sequence.md?model=0970102), [All aircraft, 103 cases](https://openairdocs.org/ntsb-events/460/sequence.md)

## Analysis

The pilot was performing a low-level aerial application flight when he momentarily and partially turned his head and body to the left to view the spray boom pressure gauge, which was located on the left spray boom. Shortly after viewing the spray boom pressure gauge, the main landing gear impacted terrain. The pilot immediately pulled up, then performed a forced landing to a flat grass field. The pilot performed an emergency shutdown and egressed the airplane without further incident. The airplane sustained substantial damage to the fuselage and both wings. The pilot reported that, in order to view the spray boom pressure gauge, he needed to look to the left and down, to about an 8 o’clock position. The pilot reported that it takes one to two seconds to view the readings accurately on the analog gauge due to the distance from the spray boom pressure gauge to the cockpit, which he estimated as about 8 ft. The pilot classified the location of the spray boom pressure gauge as a “bad design.” All the operator’s airplanes were equipped with a pressure gauge mounted on the left side spray boom, which was the only source of spray boom pressure information. The operator reported that the pressure gauges are located on the spray booms because that location provided the most reliable reading. It is likely that the pilot, while his head and body were turned to the left to view the spray boom pressure gauge, inadvertently allowed the airplane to descend and impact terrain. If the spray boom pressure was located inside the cockpit on the instrument panel, the pilot would not need to look outside of the airplane, thus diverting his attention during low-level operations. A similar accident occurred about 21 years prior, during which an airplane impacted wires after the pilot looked down to view the spray boom pressure gauge. Research indicated that some aerial application airplanes are equipped with spray boom pressure gauges inside the cockpit, or otherwise in the pilot’s forward line of sight.

## Factual narrative

On June 20, 2024, about 0706 eastern daylight time, an Ayres Corporation S2R-600 airplane, N4004K, sustained substantial damage when it was involved in an accident near Stanwood, Michigan. The commercial pilot was uninjured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 137 aerial application flight. The purpose of the flight was to apply agricultural fungicide to a potato field in a rural area. The airplane departed earlier in the morning from the operator’s facility at Lakeview Airport (13C), Lakeview, Michigan. The airplane was flying to the west, about 10 ft above ground level, traveling about 130 mph. The pilot had completed applying the liquid chemical to the potatoes and momentarily and partially turned his head and body to the left to view the spray boom pressure gauge that was located outside of the cockpit. Shortly after viewing the spray boom pressure gauge, the main landing gear impacted terrain. The pilot immediately pulled up to gain altitude. The left main landing gear was pushed up into the left wing from the impact and fuel leaked from the left wing fuel tank. The pilot performed a forced landing to a flat grass field, during which the airplane came to rest upright on the nose and forward fuselage. The pilot performed an emergency shutdown and egressed from the airplane without further incident. The airplane sustained substantial damage to the fuselage and both wings. The pilot reported there were no preimpact mechanical malfunctions or failures with the airframe or the engine that would have precluded normal operation. The pilot, who was wearing a flight helmet with a visor, reported that he did not feel fatigued during the accident flight. The pilot reported that, in order to view the spray boom pressure gauge located aft of the left flap (about mid flap) and mounted on the left spray boom, he needed to look to the left and down, to about an 8 o’clock position. The pilot reported that it took one to two seconds to view the readings accurately on the analog gauge due to the distance from the spray boom pressure gauge to the cockpit, which he estimated was about 8 ft. The pilot added that he could partially turn and view the spray boom pressure gauge while utilizing the four-point restraint system. The airplane was equipped with an Electronics International MVP-50T engine monitor system; however, this system was not configured to show spray boom pressure. The pilot, who was also a mechanic, classified the location of the spray boom pressure gauge as a “bad design.” All the operator’s airplanes, which include five Thrush S2R series airplanes, were equipped with a spray boom pressure gauge mounted on the left side spray boom, which was the only source of spray boom pressure information. The operator reported that the pressure gauges were located on the spray booms because that location provided the most reliable reading. The Federal Aviation Administration (FAA) Type Certificate for the airplane,A4SW, is currently held by Thrush Aircraft, LLC, Albany, Georgia. The restricted category airplane was originally certified to Civil Air Regulations, Part 8. A review of the FAA Type Certificate Data Sheet A4SW (revision 44) and the FAA Advisory Circular 137-1B, Certification Process for Agricultural Aircraft Operators (published on August 21, 2017), did not reveal any guidance listed about the location of the spray boom pressure gauge. According to Thrush Aircraft, airplanes manufactured since 2012 are equipped with an Electronics International MVP-50T engine monitor system that is configured to show spray boom pressure. A review of the Thrush Aircraft digital publications directory (containing service bulletins and service letters) did not reveal any guidance listed about the location of the spray boom pressure gauge. A review of the Thrush Aircraft Model S2R Illustrated Parts Catalog, applicable to the airframe serial number, showed the spray boom pressure gauge being located on the instrument panel in the cockpit. A review of the Thrush Aircraft spray boom pressure gauge installation drawing 80809-9 showed the spray boom pressure gauge as being located outside of the cockpit, just forward of the windshield, on the hopper, and in the pilot’s forward-looking line of sight. The operator reported that, when the airplane was purchased, it was not equipped with a spray boom system, nor was a spray boom pressure gauge located in the cockpit. The operator installed and configured the current spray boom system from another aerial application airplane. In 2003, an Ayres Corporation S2R-T660 airplane (serial number T660-102), which was manufactured in 2000, impacted transmission wires during a low-level spray run and was subsequently destroyed (NTSB accident number CHI03LA273). The pilot, who sustained minor injuries, reported that during the spray run, he "looked down to check pressure gauge on spray boom [and] when I looked up [the] wires were in my face."

## Aircraft

- Registration: [N4004K](https://openairdocs.org/aircraft/N4004K), registered now, S/N 2488R, built 1978 (OpenAirDocs)
- Reported make and model: AYRES CORPORATION S2R (600)
- Registry model: [Ayres S2R-600](https://openairdocs.org/model/ayres-s2r-600) (registry code 0970102) (OpenAirDocs)
- Registry engine: [AiResearch TPE331 series](https://openairdocs.org/engine/airesearch-tpe331-series) (registry code 01517, turbo-prop) (OpenAirDocs)
- Category: Airplane
- Serial number: 2488R
- Year built: 1978
- Airframe hours: 20961.67
- Engines: Honeywell TPE331-1-151 665 horsepower turbo prop
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Operator: Heritage Ag LLC, doing business as Heritage Ag LLC
- Registered owner: Heritage Ag LLC
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, April 1, 2024, 15.67 hours before
- Departed: 13C, Lakeview, MI
- Equipment: Handheld GPS, Data recorder, Stall warning system

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 41; injuries: none; commercial, private; airplane ratings: multi-engine land, single-engine sea, single-engine land; medical: class 2, without waivers/limitations; last flight review June 13, 2023; seat: single; restraint: 4-point; flight hours: 990 total, 20 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 90° at 5 knots
- Visibility: 10 statute miles
- Lowest ceiling: 700 ft overcast
- Temperature: 70 °F, dew point 68 °F
- Altimeter: 30.30 inHg
- Observed at: KRQB, 10 nm away
- METAR: KRQB 201055Z AUTO 09005KT 10SM OVC007 21/20 A3030 RMK AO2 T02140200

## 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 20240620005749A](https://openairdocs.org/incident/20240620005749A), Jun 20, 2024: Ayres Corporation S2R-600, Canadian Lakes, MI, Substantial damage. On June 20, 2024, at 0730 local time, an Ayres thrush S2R-G1 aircraft, [privacy data omitted], [privacy data omitted] and flown by a commercial rated pilot,…

## Docket (14 files)

The files NTSB released with the investigation on April 24, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=194940. 13.9 MB in all.

- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 7 pages, 2.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17591339&FileExtension=pdf&FileName=N4004K%20NTSB%20Form%206120_1_Redacted-Rel.pdf
- Various records of conversation (item 2, PDF, 6 pages, 100 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18212441&FileExtension=pdf&FileName=Various%20Records%20of%20Conversation-Rel.pdf
- N4004K - accident photographs (item 3, PDF, 10 pages, 1.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18203710&FileExtension=pdf&FileName=Accident%20Photographs-Rel.pdf
- N4004K - chemical product application report (item 4, PDF, 1 page, 482 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17591329&FileExtension=pdf&FileName=Product%20Application%20Report-Rel.pdf
- N4004K - recent airplane maintenance records (item 5, PDF, 3 pages, 1.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17532118&FileExtension=pdf&FileName=N4004K%20-%20Recent%20Maintenance%20Records_Redacted-Rel.pdf
- N4004K - airplane ownership history (item 6, PDF, 2 pages, 67 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18337658&FileExtension=pdf&FileName=CEN24LA318%20Airplane%20History%20MOR-Rel.pdf
- N4004K - spray boom pressure gauge history (item 7, PDF, 5 pages, 206 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18337684&FileExtension=pdf&FileName=CEN24LA318%20(N4004K,%20Ayres%20S2R-600)%20-%20Spray%20Boom%20Pressure%20Gauge%20Question_Redacted-Rel.pdf
- N4004K - electronics international MVP-50T postaccident engine information (item 8, PDF, 1 page, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18208015&FileExtension=pdf&FileName=N4004K%20-%20EI%20MVP-50T%20Engine%20Informaton-Rel.pdf
- N38HA - spray boom pressure gauge information (item 9, PDF, 1 page, 887 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18201482&FileExtension=pdf&FileName=N38HA%20-%20Spray%20Boom%20Pressure%20Gauge%20Information-Rel.pdf
- Thrush aircraft - spray boom pressure gauge email (item 10, PDF, 4 pages, 351 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18200640&FileExtension=pdf&FileName=CEN24LA318%20(N4004K,%20Ayres%20S2R-600)%20-%20Spray%20Boom%20Pressure%20Gauge%20Question_Redacted-Rel.pdf
- Thrush aircraft - S2R illustrated parts catalog excerpts (item 11, PDF, 10 pages, 2.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18209653&FileExtension=pdf&FileName=Thrush%20Aircraft%20-%20S2R%20Illustrated%20Parts%20Catalog%20Excerpts-Rel.pdf
- Thrush aircraft - S2R spray boom pressure gauge drawing information (item 12, PDF, 2 pages, 126 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18435395&FileExtension=pdf&FileName=CEN24LA318%20FAA%20Additional%20MOR-Rel.pdf
- Thrush aircraft - S2R airplane flight manual forced landing excerpt (item 13, PDF, 1 page, 440 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18201262&FileExtension=pdf&FileName=Thrush%20Aircraft%20S2R%20Airplane%20Flight%20Manual%20Forced%20Landing%20Excerpt-Rel.pdf
- CHI03LA273 - N4114A previous accident (item 14, PDF, 6 pages, 763 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18200886&FileExtension=pdf&FileName=CHI03LA273%20-%20Previous%20Accident-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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