# NTSB WPR11LA288: Air Tractor AT-502, N1022N, Lewistown, MT, June 25, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 24, 2011, 19:43 local (Jun 25, 2011, 01:43 UTC) - Place: Lewistown, MT - Coordinates: 47.1725, -109.671386 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=47.1725&lon=-109.6714&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report December 5, 2012 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 80898 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR11LA288 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/80898/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=80898 - Page: https://openairdocs.org/ntsb/WPR11LA288 ## Probable cause The fatigue fracture and separation of the fuel bypass line, which resulted in a total loss of engine power. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine fuel and control](https://openairdocs.org/ntsb-findings/01057300): Aircraft › Aircraft power plant · Fatigue/wear/corrosion (probable cause); cases with it: [Air Tractor AT-502, 1 case](https://openairdocs.org/ntsb-findings/01057300/cases.md?model=0390303), [All aircraft, 49 cases](https://openairdocs.org/ntsb-findings/01057300/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Air Tractor AT-502, 4 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=0390303), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Landing: 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 The pilot reported that while in cruise flight about 800 feet above ground level, the engine lost power, and he initiated a forced landing to an area of open, uneven terrain. During the landing roll, the left wing struck the ground and the airplane ground looped. Postaccident examination revealed that the fuel bypass line was fractured and had separated from the fuel control unit. Metallurgical analysis revealed that the fuel bypass line fractured near a ferrule at the edge of the braze filler metal fillet. Striations on the fracture surface were consistent with a fatigue crack originating on the outside surface of the tube and propagating toward the inside surface and circumferentially around the tube wall. No maintenance records for the airplane were recovered during the course of the investigation, and, therefore, the amount of time and maintenance history on the line was undetermined. ## Factual narrative On June 24, 2011, about 1943 mountain daylight time, an Air Tractor AT-502, N1022N, sustained substantial damage during a forced landing near Lewistown, Montana. The airplane was registered to and operated by SRB Applications, Charleston, Mississippi, under the provisions of Title 14 Code of Federal Regulations Part 137. The commercial pilot, sole occupant of the airplane, was not injured. Visual meteorological conditions prevailed and no flight plan was filed for the local aerial application flight. The flight originated from a staging area near Lewistown about 45 minutes prior to the accident. During a telephone interview with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot reported that upon completion of his aerial application on a nearby field, he was returning to the staging area to refill the airplane’s hopper. While returning, in cruise flight about 800 feet above ground level, the engine lost power and the pilot initiated a forced landing to an area of open, uneven terrain. During the landing roll, the left wing struck the ground and the airplane ground looped. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the outboard left wing was structurally damaged and buckling was observed on the fuselage between the cockpit and empennage. Local law enforcement reported that fuel was present in both wing fuel tanks. Examination of the engine revealed that the fuel bypass line, part number 3011849, was fractured and separated from the fuel control unit. The fractured fuel bypass line was removed from the engine and shipped to the NTSB Materials Laboratory, Washington, DC, for further examination. An NTSB senior metallurgist reported that the tube portion of the fuel bypass line fractured near a ferrule at the edge of the braze filler metal fillet. Fractographic evaluation revealed that the fracture initiated on the outside surface of the tube and propagated inward and circumferentially around the tube wall. Ratchet marks on the fracture surface revealed the region where the crack initiation and direction of crack propagation. The presence of ratchet marks is consistent with fatigue fracture. A scanning electron microscope was used to examine the fracture initiation region, which revealed striations consistent with fatigue crack propagation. The orientation of the fatigue striations is consistent with the fracture initiating on the outside surface of the tube and propagating towards the inside surface and circumferentially around the tube wall. No maintenance records for the airplane were recovered during the course of the investigation. ## Aircraft - Registration: [N1022N](https://openairdocs.org/aircraft/N1022N), registered now, S/N 502-0071 (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 Canada PT6A-60A](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-60a) (registry code 52043, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 502-0071 - Engines: P&W CANADA PT6A-60A 1050 horsepower turbo prop - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Srb Aerial Applicators LLC - Registered owner: Srb Aerial Applicators LLC - Departed: Lewistown, MT - Destination: Lewistown, MT - Flight plan: Unknown ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 41; injuries: none; commercial; airplane ratings: single-engine land; medical: class 2, without waivers/limitations; seat: center; flight hours: 6,200 total ## Weather - Conditions: Visual (VMC), Day - Wind: 90° at 7 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 64 °F, dew point 45 °F - Altimeter: 29.84 inHg - Observed at: LWT, 10 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 20110624011779A](https://openairdocs.org/incident/20110624011779A), Jun 24, 2011: Air Tractor Inc AT-502, Lewistown, MT, Substantial damage. On June 24, 2011, at 2016 MDT, an AT-502, N1022N, registered to srb aerial applicators, LLC, suffered an engine failure and crash landed in a wheat field 18… ## Other investigations on N1022N (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 ERA14CA030](https://openairdocs.org/ntsb/ERA14CA030), Oct 21, 2013: Air Tractor AT 502 (N1022N), Charleston, MS, substantial damage. Probable cause: The pilot's failure to maintain directional control, which resulted in a runway excursion and collision with a fence. ## Docket (3 files) The files NTSB released with the investigation on October 10, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=80898. 4.8 MB in all. - Materials Laboratory Factual Report 12-041 (with 7 embedded images) (item 1, .PDF, 2.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365769&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report%2012-041%20(with%207%20embedded%20images)-Master.PDF - Record of Conversation - Pilot (item 2, .PDF, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40374899&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20Pilot-Master.PDF - Photo 1: View of the fuel bypass line. Courtesy of the FAA. (item 3, .PDF, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40374900&FileExtension=.PDF&FileName=Photo%201%3A%20View%20of%20the%20fuel%20bypass%20line.%20Courtesy%20of%20the%20FAA.-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.