# NTSB CEN13LA341: Air Tractor AT-301, N4421S, Farnsworth, TX, June 9, 2013 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 8, 2013, 19:00 local (Jun 9, 2013, 00:00 UTC) - Place: Farnsworth, TX - Coordinates: 36.321109, -100.966392 - Nearby events: https://openairdocs.org/map.md?lat=36.3211&lon=-100.9664&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report March 13, 2014 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Lubbock FSDO - NTSB case key (mKey): 87157 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN13LA341 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/87157/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=87157 - Page: https://openairdocs.org/ntsb/CEN13LA341 ## Probable cause The partial loss of engine power for reasons that could not be determined because the postaccident engine examination revealed no anomalies. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Aircraft](https://openairdocs.org/ntsb-findings/01050000): Aircraft › Aircraft power plant · Malfunction (probable cause); cases with it: [Air Tractor AT-301, 1 case](https://openairdocs.org/ntsb-findings/01050000/cases.md?model=0390103), [All aircraft, 151 cases](https://openairdocs.org/ntsb-findings/01050000/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-301, 11 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=0390103), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/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 (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Air Tractor AT-301, 9 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=0390103), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) ## Analysis The pilot of the agricultural airplane reported that, as he was beginning a spray pass, the airplane sustained a partial loss of engine power. He attempted to dump his chemical load but was unable to maintain altitude and executed a forced landing to a field. He said that the engine continued to run smoothly but at a reduced power setting during the event. Postaccident examination of the engine revealed no anomalies that would explain the partial loss of engine power. The temperature and dew point were within a range of susceptibility for carburetor icing during glide and cruise power settings. However, the sudden reduction of power with the engine continuing to run smoothly described by the pilot was not consistent with the gradual reduction in power and rough running typically associated with carburetor icing. ## Factual narrative On June 8, 2013, about 1900 central daylight time, an Air Tractor AT-301 airplane, N4421S, sustained substantial damage to its right wing and fuselage during a forced landing following a loss of engine power near Farnsworth, Texas. The pilot was not injured. The aircraft was registered to an individual and operated by Terhune Flying Service under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The local flight originated from a private airstrip near the accident site. The pilot reported that he had flown two flights on the morning of the accident, and had to stop flight operations due to adverse weather. When the weather conditions improved he again began flight operations. The accident flight was the first flight after resuming flight operations. He reported that while starting his first spray pass, the engine lost partial power and he was unable to maintain altitude. He attempted to dump his load of chemical but the airplane continued to descend and the pilot attempted to land in a field. During the ensuing forced landing, the right main landing gear collapsed and the airplane came to rest on its nose and right wing. The pilot reported that during the event, the engine continued to run smoothly but at a reduced power output that wasn't sufficient to maintain altitude. Postaccident examination did not reveal any anomalies that would explain the partial loss of engine power. The engine was intact with no external evidence of pre-impact damage. Further examination revealed no damage to pistons, cylinders, or valves and no anomalies were noted with regard to the fuel system. The temperature and dew point recorded at a nearby airport about the time of the accident were 26 degrees Celsius and 15 degrees Celsius, respectively. According to a carburetor icing probability chart, the recorded temperature and dew point were in the range of susceptibility for carburetor icing during glide and cruise power settings. ## Aircraft - Registration: [N4421S](https://openairdocs.org/deregistered/N4421S-2018-03-14), registration cancelled 2018-03-14, S/N 301-0081 (OpenAirDocs) - Reported make and model: AIR TRACTOR INC AT-301 - Registry model: [Air Tractor AT-301](https://openairdocs.org/model/air-tractor-at-301) (registry code 0390103) (OpenAirDocs) - Category: Airplane - Serial number: 301-0081 - Airframe hours: 1138 - Engines: Pratt & Whitney R1340 AN-1 600 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Terhune Flying Service Inc - Registered owner: Dickson Shannon L DBA - Airworthiness certificate: Special, Restricted (Special) - Last inspection: 100 hour, January 10, 2013 - Departed: Farnsworth, TX - Destination: Farnsworth, TX - Flight plan: Unknown ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 34; injuries: none; commercial; airplane ratings: single-engine land, multi-engine land; medical: class 2, without waivers/limitations; seat: single ## Weather - Conditions: Visual (VMC), Day - Wind: 230° at 20 knots, gusting 25 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 79 °F, dew point 59 °F - Altimeter: 29.95 inHg - Observed at: PYX, 13 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 20130608010219A](https://openairdocs.org/incident/20130608010219A), Jun 8, 2013: Air Tractor Inc AT-301, Farnsworth, TX, Destroyed. On June 8, 2013, at 1900 local, Air tractor AT-301, bearing the registration number N4421S, impacted terrain while circling for a survey pass. The pilot stated… ## Docket (8 files) The files NTSB released with the investigation on January 22, 2014, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=87157. 2.7 MB in all. - Record of Conversation with pilot (item 1, .PDF, 53 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408001&FileExtension=.PDF&FileName=Record%20of%20Conversation%20with%20pilot-Master.PDF - Maintenance record excerpts (item 2, .PDF, 703 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408002&FileExtension=.PDF&FileName=Maintenance%20record%20excerpts-Redacted.PDF - Photo 1 View of airplane from right (item 3, .PDF, 428 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408003&FileExtension=.PDF&FileName=Photo%201%20View%20of%20airplane%20from%20right-Master.PDF - Photo 2 View from right rear (item 4, .PDF, 467 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408004&FileExtension=.PDF&FileName=Photo%202%20View%20from%20right%20rear-Master.PDF - Photo 3 View from left front (item 5, .PDF, 442 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408006&FileExtension=.PDF&FileName=Photo%203%20View%20from%20left%20front-Master.PDF - Photo 4 - View of engine (item 6, .PDF, 489 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408008&FileExtension=.PDF&FileName=Photo%204%20-%20View%20of%20engine-Master.PDF - Record of conversation with mechanic (item 7, .PDF, 53 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408015&FileExtension=.PDF&FileName=Record%20of%20conversation%20with%20mechanic-Master.PDF - FAA Carburetor Icing SAIB (item 8, .PDF, 111 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40408092&FileExtension=.PDF&FileName=FAA%20Carburetor%20Icing%20SAIB-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. --- 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.