# NTSB CEN14IA085: Beech E90, N60BA, Eau Claire, WI, December 11, 2013 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: December 11, 2013, 10:08 local (16:08 UTC) - Place: Eau Claire, WI - Coordinates: 44, -91 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=44.0000&lon=-91.0000&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Aircraft structural failure](https://openairdocs.org/ntsb-events/337) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report September 24, 2014 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA Flight Standards District Office - NTSB case key (mKey): 88550 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN14IA085 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/88550/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=88550 - Page: https://openairdocs.org/ntsb/CEN14IA085 ## Probable cause The failure of the copilot’s windshield inner layer due to a peel chip that developed as a result of mechanical and thermal expansion stresses. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Windows-windshield system: flight compartment windows](https://openairdocs.org/ntsb-findings/01035610): Aircraft › Aircraft structures · Failure (probable cause); cases with it: [Beech E-90, 1 case](https://openairdocs.org/ntsb-findings/01035610/cases.md?model=1152914), [All aircraft, 42 cases](https://openairdocs.org/ntsb-findings/01035610/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Aircraft structural failure](https://openairdocs.org/ntsb-events/337) (defining event); cases with it: [Beech E-90, 2 cases](https://openairdocs.org/ntsb-events/337/sequence.md?model=1152914), [All aircraft, 290 cases](https://openairdocs.org/ntsb-events/337/sequence.md) ## Analysis The operator reported that, while in cruise flight at flight level 190, the copilot's inner layer windshield cracked. Windshield heat was not being used at the time, and pressurization was not compromised. The pilot conducted a precautionary landing without incident. Examinations of the windshield revealed that the inner glass ply had fractured due to a peel adhesion chip at the windshield's lower forward corner. The peel chip developed as a result of the differences in coefficient of expansion between the inboard glass ply and vinyl interlayer and had propagated due to mechanical and thermal expansion stresses until the center tension of the thermally tempered glass was penetrated, which caused a spontaneous fracture. The windshield was redesigned in 2001 to reduce the thermal expansion stresses. ## Factual narrative On December 11, 2013, at 1008 central standard time, the pilot of a Beech E90, N60BA, operating as flight 25, made a precautionary landing at Chippewa Valley Regional Airport (KEAU), Eau Claire, Wisconsin, after the copilot's windshield cracked in flight. The pilot and one passenger were not injured. The airplane sustained minor damage. The airplane was registered to and operated by Bemidji Aviation Services, Inc. (BEMA), Bemidji, Minnesota, under the provisions of 14 Code of Federal Regulations Part 135 as a non-scheduled domestic passenger flight. Visual meteorological conditions prevailed at the time of the incident, and an instrument flight rules flight plan had been filed. The flight originated from Park Rapids, Minnesota, and was en route to Wheeling Illinois. According to the operator, the airplane was at FL (flight level) 190 when the copilot's inner layer windshield cracked. Windshield heat was not being used and pressurization was not compromised. The pilot put on his oxygen mask, and descended to 10,000 feet. A precautionary landing was made at KEAU without incident. The airplane was later ferried to its base in Bemidji, Minnesota. The windshield was removed and shipped to PPG Aerospace in Huntsville, Alabama, where, on May 6, 2014, it was examined under the auspices of the National Transportation Safety Board. The windshield, part number 50-420069-32 CHGA, serial # 95061H3863, was manufactured in March 1995. The inner glass ply fractured due to a peel adhesion chip at the lower forward corner of the windshield. The peel chip developed as a result of the differences in coefficient of expansion between the inboard glass ply and vinyl interlayer. The peel adhesion chip propagated, becoming wider and deeper due to mechanical and thermal stress encountered in service, until the center tension of the thermally tempered glass was penetrated causing spontaneous fracture. In 2001, PPG Aerospace redesigned the windshield adding a urethane interlayer next to the outboard surface of the inboard glass ply. This reduced the thermal expansion stresses on the glass surface. The new windshield now bears part number 50-420069-37/-38. ## Aircraft - Registration: [N60BA](https://openairdocs.org/aircraft/N60BA), registered now, S/N LW-79 (OpenAirDocs) - Reported make and model: BEECH E90 (NO SERIES) - Registry model: [Beech E-90](https://openairdocs.org/model/beech-e-90) (registry code 1152914) (OpenAirDocs) - Category: Airplane - Serial number: LW-79 - Year built: 1993 - Airframe hours: 9283 - Engines: Pratt & Whitney Canada PT6A-28 turbo prop; Pratt & Whitney Canada PT6A-28 turbo prop - Damage: Minor damage - Flight: Part 135 - Operator: Bemidji Aviation Services, Inc. - Registered owner: Bemidji Aviation Services, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Continuous airworthiness, April 20, 2013, 158 hours before - Departed: KPKD, Park Rapids, MN - Destination: KPWK, Wheeling, IL - Flight plan: IFR - Equipment: Auto-pilot, Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 47; injuries: none; airline transport, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review September 17, 2013; seat: left; restraint: 3-point; flight hours: 7,418 total, 2,200 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 280° at 7 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: -9 °F, dew point -15 °F - Altimeter: 30.44 inHg - Observed at: KEAU ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Incident 20131211024359I](https://openairdocs.org/incident/20131211024359I), Dec 11, 2013: Beech E-90, Eau Claire, WI, Minor damage. Aircraft was in flight from park rapids, MN to chicago, IL at an altitude of 19,000 feet. Co-pilot's inner heated windshield cracked to the point that… ## Docket (1 files) The files NTSB released with the investigation on August 7, 2014, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=88550. 1.2 MB in all. - PPG Aerospace, Failure Analysis Report (Approved for Distribution) (item 1, .PDF, 4 photos, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40414790&FileExtension=.PDF&FileName=PPG%20Aerospace,%20Failure%20Analysis%20Report%20(Approved%20for%20Distribution)-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.