# NTSB CEN12LA539: Gn-1 Aircamper Mathes, N31TM, Burlington, WI, August 11, 2012 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: August 11, 2012, 16:00 local (21:00 UTC) - Place: Burlington, WI - Coordinates: 42.670261, -88.270797 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=42.6703&lon=-88.2708&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) - Highest injury: Minor injuries - Injuries: 2 minor - Status: Completed, report August 13, 2013 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 84654 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN12LA539 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/84654/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=84654 - Page: https://openairdocs.org/ntsb/CEN12LA539 ## Probable cause The pilot's improper installation of the propeller bolts, which resulted in the in-flight separation of the propeller. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Mathes Tom H GN-1 AIRCAMPER, 1 case](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=05616FM), [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md) - [Propeller system](https://openairdocs.org/ntsb-findings/01046100): Aircraft › Aircraft propeller/rotor · Not specified (probable cause); cases with it: [Mathes Tom H GN-1 AIRCAMPER, 1 case](https://openairdocs.org/ntsb-findings/01046100/cases.md?model=05616FM), [All aircraft, 20 cases](https://openairdocs.org/ntsb-findings/01046100/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) (defining event); cases with it: [Mathes Tom H GN-1 AIRCAMPER, 1 case](https://openairdocs.org/ntsb-events/338/sequence.md?model=05616FM), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) - [Emergency descent: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338); cases with it: [Mathes Tom H GN-1 AIRCAMPER, 1 case](https://openairdocs.org/ntsb-events/338/sequence.md?model=05616FM), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) - [Landing: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Mathes Tom H GN-1 AIRCAMPER, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=05616FM), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Landing: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Mathes Tom H GN-1 AIRCAMPER, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=05616FM), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot departed on a local flight during which the airplane experienced an in-flight separation of the propeller. The pilot then performed a forced landing to a field that resulted in substantial damage to the fuselage. Postaccident examination of the airplane revealed that the pilot installed the propeller bolts backwards. The bolts were also found to be improperly torqued. ## Factual narrative On August 11, 2012, at 1600 central daylight time, a GN-1 Aircamper, N31TM, impacted terrain during a forced landing to a field near Burlington, Wisconsin, after the propeller with its bolts separated from the airplane during cruise flight. The certificated private pilot and a passenger received minor injuries. The airplane sustained substantial damage to the fuselage. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed and a flight plan had not been filed for the local flight that departed from Burlington Municipal Airport, Burlington, Wisconsin, about 1500. According to the Federal Aviation Administration (FAA) inspector who examined the airplane, stated that the pilot shut down the engine two times when the he experienced an in-flight vibration during a local flight. The pilot then landed the airplane on a field. The propeller was found 500 yards from the airplane. The inspector stated that the pilot installed the propeller bolts backwards and they were not properly torqued. The tachometer time at the time of the accident was 607.9 hours. The FAA inspector gave the pilot two National Transportation Safety Board (NTSB) Accident/Incident Report forms when he met the pilot. The pilot was also sent an NTSB Accident/Incident Report form by the NTSB Investigator-In-Charge. An NTSB Accident/Incident Report was not received from the pilot. ## Aircraft - Registration: [N31TM](https://openairdocs.org/deregistered/N31TM-2018-02-08), registration cancelled 2018-02-08, S/N 932 (OpenAirDocs) - Reported make and model: GN-1 AIRCAMPER MATHES - Registry model: [Mathes Tom H GN-1 AIRCAMPER](https://openairdocs.org/model/mathes-tom-h-gn-1-aircamper) (registry code 05616FM) (OpenAirDocs) - Registry engine: [Continental C85 series](https://openairdocs.org/engine/continental-c85-series) (registry code 17008, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 932 - Airframe hours: 630 - Engines: Continental C85 reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Pilot - Registered owner: Pilot - Airworthiness certificate: Special, Experimental (Special) - Departed: BUU, Burlington, WI - Destination: BUU, Burlington, WI ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 52; injuries: minor; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; last flight review August 16, 2010; seat: rear; flight hours: 695 total, 40 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 10° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 73 °F, dew point 46 °F - Altimeter: 29.96 inHg - Observed at: BUU ## 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 20120811017799A](https://openairdocs.org/incident/20120811017799A), Aug 11, 2012: Mathes Tom H GN-1 AIRCAMPER, Burlington, WI, Substantial damage. N31TM made an emergency landing in a corn field. Pilot stated that while in cruise flight, he felt a vibration, shut down the engine, restarted, and still felt… ## Docket (2 files) The files NTSB released with the investigation on July 22, 2013, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=84654. 136 KB in all. - Record of Conversation - FAA (item 1, .PDF, 24 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40391424&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20FAA-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 Letter to Pilot (item 2, .PDF, 112 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40391425&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1%20Letter%20to%20Pilot-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.