# NTSB CEN11FA562: Air Tractor AT-301, N4345S, Nekoosa, WI, August 4, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Field investigation · Final report - Date: August 4, 2011, 10:00 local (15:00 UTC) - Place: Nekoosa, WI - Coordinates: 44.3125, -89.904441 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=44.3125&lon=-89.9044&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Defining event: [Initial climb: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report March 20, 2012 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA -- Milwaukee Flight Standards - NTSB case key (mKey): 81453 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN11FA562 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/81453/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=81453 - Page: https://openairdocs.org/ntsb/CEN11FA562 ## Probable cause A total loss of engine power during initial climb for undetermined reasons. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [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. - [Initial climb: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Air Tractor AT-301, 17 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=0390103), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Air Tractor AT-301, 19 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=0390103), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The pilot reported that the engine backfired and lost power during the initial climb after takeoff. The airplane sustained substantial damage to the fuselage and wings during the forced landing. An engine teardown examination revealed a separation of three gear teeth on an intermediate gear located in the accessory section. The gear teeth exhibited signatures of overload failure; no evidence of fatigue failure was observed. Accordingly, separation of the gear teeth likely occurred during the forced landing and not as a result of a preimpact failure. No failures or malfunctions consistent with a preimpact loss of engine power were observed. At the time of the accident, carburetor icing was not probable when the airplane was under takeoff power. ## Factual narrative On August 4, 2011, about 1000 central daylight time, an Air Tractor AT-301 airplane, N4345S, was substantially damaged during a forced landing following a loss of engine power after takeoff near Nekoosa, Wisconsin. The pilot was not injured. The agricultural airplane was registered to and operated by Kafer Stone Applicator Service. The repositioning flight was being conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The flight originated from a private airstrip near Nekoosa, Wisconsin. The intended destination was a private airstrip near Oshkosh, Wisconsin. The pilot stated that the engine ran approximately 20 minutes prior to departure in order to warm up. The run-up and takeoff were normal. However, about 150 feet in the air, the engine backfired and completely lost power. He executed a forced landing to a field approximately 500 feet from the departure end of the runway. The pilot reported that his attempts to restore engine power prior to the forced landing were unsuccessful. The airplane sustained substantial damage to the fuselage and wings during the forced landing. A Federal Aviation Administration Inspector conducted an on-scene postaccident inspection. The postaccident inspection did not reveal any anomalies consistent with a preimpact loss of engine power. Fluid consistent in appearance and odor to aviation fuel was observed in the carburetor. The spark plugs exhibited signatures consistent with normal operation. The airplane was powered by a 600-horsepower Pratt & Whitney R-1340-AN-1 radial engine, serial number ZP-101988. An engine overhaul was completed in March 2000. An annual inspection was completed on June 20, 2011. At the time of the accident, the engine had accumulated about 7,382 hours total time, with approximately 566 hours since overhaul. About 17 hours had accumulated since the annual inspection. The NTSB Investigator-in-Charge (IIC) supervised a full engine teardown examination. The teardown examination revealed the separation of three gear teeth on a 10:1 gear (part number 14951) located in the accessory section of the engine. The remaining gear teeth appeared to be intact and undamaged. No other anomalies were observed during the teardown examination. Metallurgical review of the fractured gear teeth noted the presence of overload failure signatures on the fracture surfaces. No indications of fatigue failure were observed. A representative of the engine overhaul facility stated that the 10:1 gear (p/n 14951) identified during the teardown examination functioned as an intermediate gear between the engine crankshaft floating gear and the supercharger impeller gear. Separation of several gear teeth is common in the case of a propeller strike event, such as during a forced landing. Failure of the gear in-flight commonly results in damage to the remainder of the gear. Weather conditions at the AlexanderSouth Wood County Airport (ISW), located about 5 miles northeast of the accident site, at 0954, were recorded as: wind from 130 degrees at 5 knots, clear sky, 10 miles visibility, temperature 25 degrees Celsius, dew point 18 degrees Celsius, and altimeter 30.02 inches of mercury. Federal Aviation Administration guidance indicated a possibility of engine carburetor icing only at glide power based on the recorded weather conditions. ## Aircraft - Registration: [N4345S](https://openairdocs.org/deregistered/N4345S-2021-05-08), registration cancelled 2021-05-08, S/N 301-0025, built 1975 (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) - Registry engine: [Pratt & Whitney R1340 series](https://openairdocs.org/engine/pratt-whitney-r1340-series) (registry code 52016, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 301-0025 - Airframe hours: 7382 - Engines: P&W R-1340-AN-1 600 horsepower reciprocating - Damage: Substantial damage - Flight: Positioning, Part 91 - Operator: Kafer Stone Applicator Service Inc. - Registered owner: Kafer Stone Applicator Service Inc. - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, June 20, 2011, 17 hours before - Departed: PVT, Nekoosa, WI - Destination: PVT, Oshkosh, WI - Airport: PVT, Private, runway 36, 2,500 × 50 ft, grass/turf ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 53; injuries: none; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review March 11, 2011; seat: single; flight hours: 885 total, 35 in this make and model, 820 as pilot in command, 145 in the last 90 days, 55 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 130° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 77 °F, dew point 64 °F - Altimeter: 30.02 inHg - Observed at: ISW, 5 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 20110804016979A](https://openairdocs.org/incident/20110804016979A), Aug 4, 2011: Air Tractor Inc AT-301, Nekoosa, WI, Substantial damage. Pilot reported this was to be a repositioning flight to their grass strip 30 miles to the east. First flight of the dayapprox 50 gallons of fuel was on board… ## Docket (9 files) The files NTSB released with the investigation on February 8, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=81453. 7.1 MB in all. - Pilot Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 381 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361565&FileExtension=.PDF&FileName=Pilot%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Operator Aircraft Accident Report, NTSB Form 6120.1 (item 2, .PDF, 308 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361567&FileExtension=.PDF&FileName=Operator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Airplane Maintenance Logbook (item 3, .PDF, 203 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361569&FileExtension=.PDF&FileName=Airplane%20Maintenance%20Logbook-Redacted.PDF - Engine Maintenance Logbook (item 4, .PDF, 5.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361570&FileExtension=.PDF&FileName=Engine%20Maintenance%20Logbook-Redacted.PDF - Conversation Record -- FAA Inspector (item 5, .PDF, 48 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361687&FileExtension=.PDF&FileName=Conversation%20Record%20--%20FAA%20Inspector-Master.PDF - Conversation Record -- NTSB Metallurgist (item 6, .PDF, 58 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361801&FileExtension=.PDF&FileName=Conversation%20Record%20--%20NTSB%20Metallurgist-Master.PDF - Conversation Record -- Engine Overhaul Facility (item 7, .PDF, 49 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361686&FileExtension=.PDF&FileName=Conversation%20Record%20--%20Engine%20Overhaul%20Facility-Master.PDF - Weather Observations -- Alexander Field South County Airport (item 8, .PDF, 24 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361685&FileExtension=.PDF&FileName=Weather%20Observations%20--%20Alexander%20Field%20South%20County%20Airport-Master.PDF - FAA Safety Bulletin -- Carburetor Icing (item 9, .PDF, 86 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40361572&FileExtension=.PDF&FileName=FAA%20Safety%20Bulletin%20--%20Carburetor%20Icing-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.