# NTSB CEN11LA460: Ayres S2R600, N3101S, Pine Bluff, AR, July 6, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 6, 2011, 10:30 local (15:30 UTC) - Place: Pine Bluff, AR - Coordinates: 34.137222, -91.871665 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.1372&lon=-91.8717&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Defining event: [Initial climb: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report February 12, 2013 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA Little Rock FSDO, Honeywell Aerospace - NTSB case key (mKey): 81034 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN11LA460 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/81034/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=81034 - Page: https://openairdocs.org/ntsb/CEN11LA460 ## Probable cause The use of an incorrect mounting bolt by maintenance persons to attach the engine torque sensor, which resulted in an internal failure of the torque sensor and subsequent loss of engine power due to fuel starvation. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (turbine/turboprop): accessory drives](https://openairdocs.org/ntsb-findings/01057260): Aircraft › Aircraft power plant · Malfunction (probable cause); cases with it: [Ayres S2R-G6, 1 case](https://openairdocs.org/ntsb-findings/01057260/cases.md?model=0970216), [All aircraft, 12 cases](https://openairdocs.org/ntsb-findings/01057260/cases.md) - [Engine (turbine/turboprop): accessory drives](https://openairdocs.org/ntsb-findings/01057260): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Ayres S2R-G6, 1 case](https://openairdocs.org/ntsb-findings/01057260/cases.md?model=0970216), [All aircraft, 12 cases](https://openairdocs.org/ntsb-findings/01057260/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Aircraft maintenance event](https://openairdocs.org/ntsb-events/040); cases with it: [Ayres S2R-G6, 1 case](https://openairdocs.org/ntsb-events/040/sequence.md?model=0970216), [All aircraft, 484 cases](https://openairdocs.org/ntsb-events/040/sequence.md) - [Initial climb: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Ayres S2R-G6, 4 cases](https://openairdocs.org/ntsb-events/340/sequence.md?model=0970216), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Initial climb: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341); cases with it: [Ayres S2R-G6, 2 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=0970216), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Other: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Ayres S2R-G6, 4 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=0970216), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Other: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Ayres S2R-G6, 8 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=0970216), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis After the airplane sustained a complete loss of engine power during initial climb, the pilot performed an off-airport landing. Postaccident examination revealed that three teeth in the torque sensor spur gear separated after four of the five torque sensor mounting bolts became loose. The loose bolts caused the torque sensor housing to move radially away from the gear case, causing the teeth to overload and separate. Subsequently, the engine’s fuel pump and fuel control were no longer driven by the gears in the gear train, which were normally driven by the torque sensor spur gear, thus the engine was starved of fuel. Metallurgical examination showed that the bolts became loose because a bolt that was undersized and of the incorrect configuration had been installed. A maintenance record showed that the engine had previously been disassembled due to a torque sensor failure and an overhauled torque sensor had been reinstalled. ## Factual narrative On July 6, 2011, about 1030 central daylight time, an Ayres S2R600 G6, single engine airplane, N3101S, was substantially damaged when it impacted terrain following a complete loss of engine power during initial climb near Pine Bluff, Arkansas. The airplane was owned and operated by Swan Lake Flying Service, Inc. The pilot reported no injuries. Visual meteorological conditions prevailed and a flight plan had been not filed for the 14 Code of Federal Regulations Part 137 agricultural flight. At the time of the accident the airplane was departing from Ladd Airstrip, Pine Bluff, Arkansas, for a local flight. The pilot reported that his take-off and initial climb were normal. He had started a turn and was about 150 feet above ground level when the engine suddenly quit producing power. The pilot performed a forced landing near the end of the runway, impacted terrain and a drainage ditch, and came to rest upright. The impact resulted in substantial damage to the engine mounts and forward fuselage and both main landing gear partially separated from the airplane. Airframe and engine maintenance logbooks were not available for examination. One maintenance record from a repair facility showed that the engine from the airplane had been disassembled and repaired three years previously following a torque sensor failure. The record showed that the torque sensor and several other parts had been installed in the engine in an overhauled condition. The repaired engine was approved for a return to service on September 13, 2008, and was reinstalled on the airplane A postaccident examination of the engine disclosed that four of five torque sensor assembly mounting bolts were loose. One of the loose bolts holding the torque sensor was undersized, of the incorrect configuration, and was not the part specified. The torque sensor in the engine was the same serial numbered part listed in the September 13, 2008, maintenance record. Heavy wear was observed on the torque sensor housing around two bolt holes and the mounting hardware that corresponded with the two holes was also worn. The difference in bolt shank diameter displayed motion of the torque sensor housing relative to the gear case as evidenced by the separation of anti-rotation tabs which left deep wear grooves in the torque sensor housing and were indicative of tab contact. Three teeth were found separated from the torque sensor spur gear. The torque sensor spur gear is part of an assembly that drives the fuel pump and fuel control. Metallurgical examination showed that the failure mode of the separated teeth exhibited distinct features indicative of high cycle fatigue initiation and tip loading of the gear teeth after the torque sensor mounting bolts became loose. According to the manufacturer, when the engine fuel pump and fuel control are no longer driven by the gears in the gear train, which are driven by the torque sensor spur gear, the engine will stop running. ## Aircraft - Registration: [N3101S](https://openairdocs.org/deregistered/N3101S-2014-05-19), registration cancelled 2014-05-19, S/N G6-106, built 1992 (OpenAirDocs) - Reported make and model: AYRES S2R600 (G6) - Registry model: [Ayres S2R-G6](https://openairdocs.org/model/ayres-s2r-g6) (registry code 0970216) (OpenAirDocs) - Registry engine: [AiResearch TPE331-5&6SER](https://openairdocs.org/engine/airesearch-tpe331-5-6ser) (registry code 01515, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: G6-106 - Airframe hours: 7467 - Engines: GARRETT TPE331 750 hp turbo prop - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Swan Lake Flying Service, Inc. - Registered owner: Swan Lake Flying Service, Inc. - Airworthiness certificate: Special, Restricted (Special) - Last inspection: 100 hour, June 21, 2011, 20 hours before - Departed: Pine Bluff, AR - Destination: Pine Bluff, AR - Airport: Ladd Airstrip, runway 09, 3,900 × 40 ft, gravel ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 54; injuries: minor; flight engineer, flight instructor, airline transport; airplane ratings: single-engine sea, single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review February 17, 2011; seat: single; flight hours: 35,000 total, 250 in this make and model, 250 in the last 90 days, 150 in the last 30 days, 9 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: variable at 4 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 70 °F - Altimeter: 30.01 inHg - Observed at: KPBF, 3 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 20110706013769A](https://openairdocs.org/incident/20110706013769A), Jul 6, 2011: Ayres Corporation S2R-G6, Swan Lake, AR, Substantial damage. On July 6, 2011, at 1045 CST, an Ayres S2R-G6, N3101S, registered to Swan Lake flying service, inc. performed an emergency off airport landing near Swan Lake,… ## Docket (8 files) The files NTSB released with the investigation on December 17, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=81034. 5.5 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 674 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350810&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Map (item 2, .PDF, 117 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40383164&FileExtension=.PDF&FileName=Map-Master.PDF - Photo - Wreckage as viewed from the right side (FAA Photo) (item 3, .PDF, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40383169&FileExtension=.PDF&FileName=Photo%20-%20Wreckage%20as%20viewed%20from%20the%20right%20side%20%20(FAA%20Photo)-Master.PDF - Engine Maintenance Log Entry on September 13, 2008 (item 4, .PDF, 119 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40383171&FileExtension=.PDF&FileName=Engine%20Maintenance%20Log%20Entry%20on%20September%2013,%202008-Redacted.PDF - Reports from Parties to the Investigation - Honeywell Wreckage Review Notes (item 5, .PDF, 29 photos, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40383173&FileExtension=.PDF&FileName=Reports%20from%20Parties%20to%20the%20Investigation%20-%20Honeywell%20Wreckage%20Review%20Notes-Master.PDF - Reports from Parties to the Investigation - Honeywell Engine Examination Report (selected pages) (item 6, .PDF, 44 photos, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40383174&FileExtension=.PDF&FileName=Reports%20from%20Parties%20to%20the%20Investigation%20-%20Honeywell%20Engine%20Examination%20Report%20%20(selected%20pages)-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 7, .PDF, 115 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40383170&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 8, .PDF, 465 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40383172&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.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.