# NTSB CEN12LA470: Yamokoski William Glastar, N4970Y, Chicago, IL, July 22, 2012 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: July 22, 2012, 13:30 local (18:30 UTC) - Place: Chicago, IL - Coordinates: 41.609722, -87.407775 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=41.6097&lon=-87.4078&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report December 19, 2012 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA/FSDO - NTSB case key (mKey): 84422 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN12LA470 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/84422/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=84422 - Page: https://openairdocs.org/ntsb/CEN12LA470 ## Probable cause Failure of the automotive engine's reduction gearbox while in cruise flight. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Accessory gear-boxes](https://openairdocs.org/ntsb-findings/01058300): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Yamokoski William GLASTAR, 1 case](https://openairdocs.org/ntsb-findings/01058300/cases.md?model=05614QM), [All aircraft, 19 cases](https://openairdocs.org/ntsb-findings/01058300/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Yamokoski William GLASTAR, 1 case](https://openairdocs.org/ntsb-events/340/sequence.md?model=05614QM), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Yamokoski William GLASTAR, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=05614QM), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Landing-landing roll: Nose over/nose down](https://openairdocs.org/ntsb-events/096); cases with it: [Yamokoski William GLASTAR, 1 case](https://openairdocs.org/ntsb-events/096/sequence.md?model=05614QM), [All aircraft, 2,287 cases](https://openairdocs.org/ntsb-events/096/sequence.md) ## Analysis The pilot was on a cross-country flight in an experimental airplane when the engine began to “race.” The pilot tried to reduce power by adjusting the throttle, but the engine and propeller were unresponsive. He then made a forced landing to a soft field, and the airplane nosed over. Examination of the automotive engine revealed that the spline-shaft and adapter gears in the reduction gearbox were worn, which resulted in the gearbox's failure. According to the pilot, the gearbox was not a regularly inspected item for this particular engine/gearbox combination. At the time it failed, the gearbox had accrued 247 total hours since new. ## Factual narrative On June 22, 2012, at 1330 central daylight time, an experimental-amateur built Yamokoski Glastar was substantially damaged after it made a forced landing to a field in Chicago, Illinois. The private pilot/owner/builder sustained minor injuries. No flight plan was filed for the flight that departed Wittman Regional Airport (OSH), Osh Kosh, Wisconsin, around 1200 and was destined for Southwest Michigan Regional Airport (BEH), Benton Harbor, Michigan. Visual meteorological conditions prevailed for the personal flight conducted under 14 Code of Federal Regulations Part 91. The pilot said he was following the shoreline back to Michigan when he heard and felt two "thumps" from the engine compartment. Approximately 10 seconds later, the pilot heard another thump and the engine RPM began to race. The pilot tried to reduce power by adjusting the throttle, but the engine and propeller were unresponsive. The pilot made a forced landing to a soft field and the airplane nosed-over damaging the right wing strut and the vertical stabilizer. Examination of the automotive engine revealed that the spline-shaft and adapter gears in the reduction gearbox were worn, which caused the gearbox to fail. The pilot reported that the gearbox was not a regularly inspected item for this particular engine/gearbox combination. The gearbox was installed new and had only accrued 247 hours at the time of the accident. ## Aircraft - Registration: [N4970Y](https://openairdocs.org/aircraft/N4970Y), registered now, S/N 5377, built 2002 (OpenAirDocs) - Reported make and model: YAMOKOSKI WILLIAM GLASTAR - Registry model: [Yamokoski William GLASTAR](https://openairdocs.org/model/yamokoski-william-glastar) (registry code 05614QM) (OpenAirDocs) - Registry engine: [Subaru ALL MDLS A/B](https://openairdocs.org/engine/subaru-all-mdls-a-b) (registry code 59050, 4 cycle) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 5377 - Airframe hours: 1424 - Engines: SUBARU Boxer 2.5L 400 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Yamokoski William - Registered owner: Yamokoski William - Airworthiness certificate: Special, Experimental (Special); Standard, Normal - Last inspection: Condition, October 25, 2011, 87 hours before - Departed: OSH, Osh Kosh, WI - Destination: BEH, Benton Harbor, MI - Airport: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 63; injuries: minor; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, unknown; last flight review May 29, 2010; seat: left; flight hours: 1,515 total, 1,424 in this make and model, 47 in the last 90 days, 25 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Visibility: 10 statute miles - Lowest ceiling: none ## 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 20120722016159A](https://openairdocs.org/incident/20120722016159A), Jul 22, 2012: Yamokoski William GLASTAR, Chicago, IL, Substantial damage. On July 22, 2012, at approximately 13:00 CDT, N4970Y an experimental amateur built Glastar, enroute from oshkosh, WI to benton harbor, mi declared an emergency… ## Other investigations on N4970Y (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 CHI05CA236](https://openairdocs.org/ntsb/CHI05CA236), Aug 21, 2005: Yamokoski Glastar (N4970Y), Marcellus, MI, substantial damage. Probable cause: The in-flight loss of engine power during cruise for undetermined reasons and the unsuitable terrain the pilot encountered during the forced landing. A factor was the tall corn he encountered. ## Docket (3 files) The files NTSB released with the investigation on October 23, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=84422. 1.4 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40378684&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Record of Conversation - Pilot (item 2, .PDF, 73 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40379759&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20Pilot-Master.PDF - Record of Conversation -FAA Inspector (item 3, .PDF, 61 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40378656&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-FAA%20Inspector-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.