# NTSB CEN11LA593: Air Tractor AT-400, N23720, Monango, ND, August 23, 2011

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Limited investigation · Final report
- Date: August 23, 2011, 18:53 local (23:53 UTC)
- Place: Monango, ND
- Coordinates: 46.183612, -98.507774
- Nearby events: https://openairdocs.org/map.md?lat=46.1836&lon=-98.5078&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: Serious injuries
- Injuries: 1 serious
- Status: Completed, report May 15, 2012
- Report: Approved by Office Director
- NTSB office: Central Region
- Parties: Federal Aviation Administration - Fargo FSDO
- NTSB case key (mKey): 81596
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN11LA593
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/81596/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=81596
- Page: https://openairdocs.org/ntsb/CEN11LA593

## Probable cause

The pilot did not maintain adequate separation from a tree during the aerial-application flight.

## Findings

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

- [Performance/control parameters: altitude](https://openairdocs.org/ntsb-findings/01062012): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Air Tractor AT-400, 2 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md?model=0390202), [All aircraft, 1,310 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md)
- [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Air Tractor AT-400, 1 case](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=0390202), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md)
- [Object/animal/substance: tree(s)](https://openairdocs.org/ntsb-findings/03022020): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Air Tractor AT-400, 1 case](https://openairdocs.org/ntsb-findings/03022020/cases.md?model=0390202), [All aircraft, 933 cases](https://openairdocs.org/ntsb-findings/03022020/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: Low altitude operation/event](https://openairdocs.org/ntsb-events/220) (defining event); cases with it: [Air Tractor AT-400, 2 cases](https://openairdocs.org/ntsb-events/220/sequence.md?model=0390202), [All aircraft, 780 cases](https://openairdocs.org/ntsb-events/220/sequence.md)

## Analysis

The pilot reported that he remembered completing a majority of his spray runs during the aerial-application flight and was finishing along the field's edge when the accident occurred. However, he had no recollection of the airplane colliding with the trees or terrain. Global positioning system data revealed that the airplane had descended from about 300 feet above ground level (agl) to less than 100 feet agl into a sparsely wooded area during the last 15 seconds of the flight. A postaccident examination established that the airplane's right wingtip contacted a tree before the airplane collided with terrain. The examination did not reveal any mechanical malfunctions or failures that would have precluded normal operation of the airplane. The presence of fuel throughout the engine's fuel system and the rotational damage sustained by several engine components was consistent with a sudden stoppage of an operating engine during impact.

## Factual narrative

On August 23, 2011, at 1853 central daylight time, an Air Tractor AT-400, N23720, was substantially damaged when it collided with trees and terrain near Monango, North Dakota. The pilot sustained serious injuries. The airplane was registered to and operated by D-Lux Spray Service, LLC, under the provisions of 14 Code of Federal Regulations Part 137. Day visual meteorological conditions prevailed for the flight, which was operated without a flight plan. The aerial-application flight departed Edgeley Municipal Airport (51D) at approximately 1819. The pilot reported that he remembered completing a majority of his spray runs and was finishing along the field's edge when the accident occurred; however, he had no recollection of the airplane colliding with the trees or terrain. A postaccident examination conducted by Federal Aviation Administration inspectors established that the airplane's right wingtip contacted a cottonwood tree before the airplane collided with terrain. There was a wreckage debris path, about 100 yards long, preceding the main wreckage which was located in a roadside ditch. The debris path contained fragmented portions of the airframe, wings, and tree branches. The fuselage and wings were substantially damaged during the accident sequence. There was no evidence of a postimpact fire. The east/west power transmission line, situated along the north side of the roadway, appeared undamaged. The postaccident examination did not reveal any mechanical malfunctions or failures that would have precluded normal operation of the airplane. The engine fuel control unit (FCU), fuel filter bowl, flow divider, and fuel lines contained fuel. The splined driveshaft connecting the fuel pump to the accessory gearbox was sheared and exhibited rotational damage. The nylon coupler between the fuel pump and the FCU exhibited fracture features consistent with torsion overload. The engine compressor section, FCU flyweights, and propeller exhibited rotational damage consistent with a sudden stoppage event. A handheld global positioning system (GPS) receiver was found at the accident site. The position data downloaded from the GPS device showed the airplane departing 51D approximately 34 minutes before the accident. After departure, the airplane flew about 16 miles southeast to the field contracted to be sprayed. The plotted data was consistent with aerial application maneuvers being performed during the remainder of the accident flight. The last 15 seconds of GPS data showed the airplane on west-northwest heading descending from approximately 300 feet above ground level (agl) to less than 100 feet agl. The final two data points were located amongst a sparsely wooded area when plotted on an aerial-survey image. At 1855, the automated surface observing system at the Gwinner-Roger Melroe Field Airport, located about 41 miles east of the accident site, reported the following weather conditions: wind 210 degrees at 9 knots; visibility 10 miles; clear skies;temperature 30 degrees Celsius; dew point 25 degrees Celsius; altimeter setting 29.61 inches of mercury.

## Aircraft

- Registration: [N23720](https://openairdocs.org/deregistered/N23720-2018-01-16), registration cancelled 2018-01-16, S/N 400-0422, built 1981 (OpenAirDocs)
- Reported make and model: Air Tractor, Inc. AT-400
- Registry model: [Air Tractor AT-400](https://openairdocs.org/model/air-tractor-at-400) (registry code 0390202) (OpenAirDocs)
- Registry engine: [Pratt & Whitney PT6A series](https://openairdocs.org/engine/pratt-whitney-pt6a-series) (registry code 52034, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 400-0422
- Airframe hours: 9354
- Engines: Pratt & Whitney PT6A-15AG 680 horsepower turbo prop
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Operator: D-Lux Spray Service, LLC
- Registered owner: David J. Lux
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, July 29, 2011
- Departed: 51D, Edgeley, ND
- Destination: 51D, Edgeley, ND

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 46; injuries: serious; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review January 27, 2010; seat: center; flight hours: 3,645 total, 1,051 in this make and model, 3,645 as pilot in command, 175 in the last 90 days, 50 in the last 30 days, 6 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 210° at 9 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 86 °F, dew point 77 °F
- Altimeter: 29.61 inHg
- Observed at: KGWR, 36 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 20110823018369A](https://openairdocs.org/incident/20110823018369A), Aug 23, 2011: Air Tractor Inc AT-400, Monago, ND, Destroyed. Pilot was spraying field NE of Monago ndin a "race track" type spray pattern. Sprayed 3 fields going east and west north of 85th st, then was spraying last…

## Other investigations on N23720 (1)

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.

- [NTSB CHI06CA221](https://openairdocs.org/ntsb/CHI06CA221), Jul 31, 2006: Air Tractor AT-400 (N23720), Springfield, MN, substantial damage. Probable cause: The pilot's inability to maintain directional control of the airplane as a result of the partial failure of the tail wheel assembly. A factor associated with the accident was the crop that the…

## Docket (6 files)

The files NTSB released with the investigation on April 9, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=81596. 1.8 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 881 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364695&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF
- Memorandum of Conversation (FAA Inspectors Allen and Emerson) (item 2, .PDF, 58 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364696&FileExtension=.PDF&FileName=Memorandum%20of%20Conversation%20(FAA%20Inspectors%20Allen%20and%20Emerson)-Master.PDF
- FAA Inspector Statements (item 3, .PDF, 492 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364697&FileExtension=.PDF&FileName=FAA%20Inspector%20Statements-Redacted.PDF
- Global Positioning System Data Plot (item 4, .PDF, 251 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364698&FileExtension=.PDF&FileName=Global%20Positioning%20System%20Data%20Plot-Master.PDF
- Global Positioning System Source Data (item 5, .PDF, 69 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364699&FileExtension=.PDF&FileName=Global%20Positioning%20System%20Source%20Data-Master.PDF
- Weather Reports (item 6, .PDF, 42 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364700&FileExtension=.PDF&FileName=Weather%20Reports-Master.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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