# NTSB CEN11LA429: Keesler W8 Tailwind, N56PK, Oshkosh, WI, June 29, 2011 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: June 29, 2011, 10:03 local (15:03 UTC) - Place: Oshkosh, WI - Coordinates: 43.984443, -88.556945 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=43.9844&lon=-88.5569&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Defining event: [Initial climb: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report February 23, 2012 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Federal Aviation Administration - Milwaukee FSDO - SAIBs cited in the narratives: [SAIB CE-09-35](https://openairdocs.org/saib/CE-09-35) (OpenAirDocs) - NTSB case key (mKey): 80940 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN11LA429 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/80940/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=80940 - Page: https://openairdocs.org/ntsb/CEN11LA429 ## Probable cause The loss of engine power during initial climb for undetermined reasons. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Terrain: rough terrain](https://openairdocs.org/ntsb-findings/03021015): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Keesler Patrick E W8 TAILWIND, 1 case](https://openairdocs.org/ntsb-findings/03021015/cases.md?model=97902PK), [All aircraft, 442 cases](https://openairdocs.org/ntsb-findings/03021015/cases.md) - [Engine (reciprocating)](https://openairdocs.org/ntsb-findings/01058500): Aircraft › Aircraft power plant · Not specified (probable cause); cases with it: [Keesler Patrick E W8 TAILWIND, 1 case](https://openairdocs.org/ntsb-findings/01058500/cases.md?model=97902PK), [All aircraft, 497 cases](https://openairdocs.org/ntsb-findings/01058500/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 (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Keesler Patrick E W8 TAILWIND, 1 case](https://openairdocs.org/ntsb-events/342/sequence.md?model=97902PK), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Landing: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Keesler Patrick E W8 TAILWIND, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=97902PK), [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: [Keesler Patrick E W8 TAILWIND, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=97902PK), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The accident occurred during the initial flight testing of the experimental amateur-built airplane. The pilot reported that, during the initial climb, at an altitude of about 200 feet above the ground, the engine began to lose power. He notified the tower air traffic controller of his engine emergency and began a turn to remain clear of nearby buildings. The airplane encountered a ditch during the forced landing and the forward fuselage and firewall were substantially damaged. The airframe had accumulated 4 hours since it was issued an airworthiness certificate and the engine had accumulated 5.7 hours since its last major overhaul. The pilot/builder replaced the carburetor, spark plugs, and a cylinder since the last engine overhaul. A postaccident examination of the engine revealed that both spark plugs for the No. 4 cylinder were loosely installed into the cylinder head. The upper spark plug for the No. 4 cylinder was not seated on its cylinder gasket. Several spark plugs were removed and exhibited features consistent with the engine operating at a rich carburetor mixture setting. Although a carburetor-icing probability chart indicated that there was a serious potential for carburetor ice accumulation while operating at a reduced engine power setting, the postaccident investigation could not determine if carburetor ice contributed to the loss of engine power. The postaccident investigation was unable to determine the reason for the loss of engine power, which could have been a result of the incorrectly installed spark plugs on the No. 4 cylinder, an excessively rich carburetor mixture setting, an accumulation of carburetor ice before takeoff, or any combination of the aforementioned issues. ## Factual narrative On June 29, 2011, at 1003 central daylight time, an experimental amateur-built Keesler W8 Tailwind airplane, N56PK, was substantially damaged during a forced landing at Wittman Regional Airport (KOSH), Oshkosh, Wisconsin. The pilot sustained minor injuries. The airplane was registered to and operated by the private pilot under the provisions of 14 Code of Federal Regulations Part 91. Day visual meteorological conditions prevailed for the flight, which was operated without a flight plan. The local flight was originating at the time of the accident. The pilot reported that the accident flight was the first flight in the accident airplane in over 6 months, during which time he had been modifying the airplane. The purpose of the flight was to orbit the airport while he evaluated the various airframe and engine systems. The pilot stated that during initial climb from runway 9, at an altitude of about 200 feet above the ground, the engine began to lose power. He notified the control tower of his engine emergency and began a turn to the south to remain clear of nearby buildings. The airplane landed in a grassy area to the south of runway 9, boarded by taxiways Juliet and Kilo. The forward fuselage and firewall were substantially damaged when the airplane encountered a ditch, collapsing the main landing gear. According to available documentation, the airplane was issued its airworthiness certificate on May 19, 2010, and had completed 4.0 hours of its required 40 hour phase I flight testing when the accident occurred. A conditional inspection was completed on June 27, 2011, at 3.9 hours total airframe time. The last recorded flight was completed on November 10, 2010. The engine, a Continental Motors model C-90-12F, had accumulated 5.7 hours since its last major overhaul, which was completed on January 2, 2009. The carburetor and spark plugs were replaced by the pilot/builder on September 7, 2010. The No. 2 cylinder was replaced by the pilot/builder on October 18, 2010. The last recorded engine maintenance was an oil change that was completed on June 1, 2011. A postaccident engine examination revealed that both spark plugs for the No. 4 cylinder were loosely installed into the cylinder head. The upper plug for the No. 4 cylinder was not seated on its cylinder gasket. Several spark plugs were removed and exhibited features consistent with the engine operating at a rich carburetor mixture setting. Both magnetos provided spark when rotated. Mechanical continuity was confirmed from the cockpit engine controls to their respective engine components. The carburetor heat control was in the off position. The carburetor bowl contained fuel with no evidence of water contamination. At 1011, the airport's automated surface observing system reported the following weather conditions: wind 180 degrees at 3 knots; visibility 10 miles; clear skies; temperature 21 degrees Celsius; dew point 13 degrees Celsius; altimeter setting 30.15 inches of mercury. The carburetor icingprobability chart included in Federal Aviation Administration Special Airworthiness Information Bulletin No. CE-09-35, Carburetor Icing Prevention, indicated that there was a potential for serious carburetor icing while operating at glide power. ## Aircraft - Registration: [N56PK](https://openairdocs.org/deregistered/N56PK-2018-01-10), registration cancelled 2018-01-10, S/N 1953, built 2010 (OpenAirDocs) - Reported make and model: Keesler W8 Tailwind - Registry model: [Keesler Patrick E W8 TAILWIND](https://openairdocs.org/model/keesler-patrick-e-w8-tailwind) (registry code 97902PK) (OpenAirDocs) - Registry engine: [Continental C90-12F](https://openairdocs.org/engine/continental-c90-12f) (registry code 17183, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 1953 - Airframe hours: 4 - Engines: Continental Motors C-90-12F 90 horsepower reciprocating - Damage: Substantial damage - Flight: Flight test, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, June 27, 2011 - Departed: KOSH, Oshkosh, WI - Destination: KOSH, Oshkosh, WI - Airport: KOSH, Wittman Regional Airport, runway 09, 6,178 × 150 ft, concrete ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 58; injuries: minor; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; last flight review May 25, 2010; seat: left; flight hours: 283 total, 4 in this make and model, 213 as pilot in command, 0 in the last 90 days, 0 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 180° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 70 °F, dew point 55 °F - Altimeter: 30.14 inHg - Observed at: KOSH ## 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 20110629011639A](https://openairdocs.org/incident/20110629011639A), Jun 29, 2011: Keesler Patrick E W8 TAILWIND, Oshkosh, WI, Substantial damage. On June 29, 2011 at approximately 10:00 am pilot [privacy data omitted] was cleared to depart runway 9 at Wittman Regional Airport for flight testing. A few… ## Docket (9 files) The files NTSB released with the investigation on December 27, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=80940. 1.2 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 367 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40360067&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - FAA Inspector Statement (Connie Martin) (item 2, .PDF, 40 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40360069&FileExtension=.PDF&FileName=FAA%20Inspector%20Statement%20(Connie%20Martin)-Redacted.PDF - Airport Diagram (item 3, .PDF, 136 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40360082&FileExtension=.PDF&FileName=Airport%20Diagram-Master.PDF - Airframe Logbook, Excerpts (item 4, .PDF, 108 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40360112&FileExtension=.PDF&FileName=Airframe%20Logbook,%20Excerpts-Redacted.PDF - Engine Logbook, Excerpts (item 5, .PDF, 77 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40360098&FileExtension=.PDF&FileName=Engine%20Logbook,%20Excerpts-Redacted.PDF - Pilot Logbook, Excerpts (item 6, .PDF, 219 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40360099&FileExtension=.PDF&FileName=Pilot%20Logbook,%20Excerpts-Redacted.PDF - Weather Reports (item 7, .PDF, 42 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40360070&FileExtension=.PDF&FileName=Weather%20Reports-Master.PDF - Carburetor Icing Probability Chart (item 8, .PDF, 128 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40360071&FileExtension=.PDF&FileName=Carburetor%20Icing%20Probability%20Chart-Master.PDF - Special Airworthiness Information Bulletin No. CE-09-35, Carburetor Icing Prevention (item 9, .PDF, 111 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40360081&FileExtension=.PDF&FileName=Special%20Airworthiness%20Information%20Bulletin%20No.%20CE-09-35,%20Carburetor%20Icing%20Prevention-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.