>>4377485
DOT/FAA/AR-05/34
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Government Accession No. 3. Recipient's Catalog No.
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Report Date
September 2005
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Title and Subtitle
HIGH-SPEED BOLTHOLE EDDY-CURRENT SCANNING FOR IN-SERVICE INSPECTION OF ENGINE DISKS 6. Performing Organization Code
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Author(s)
Lisa Brasche2, Tony Mellors, Thadd Patton3, Rob Stephen, Kevin Smith4 , Andy Kinney, Waled Hassan, Jim Ohm, and Joel Schraan1
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Performing Organization Report No.
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Work Unit No. (TRAIS)
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Performing Organization Name and Address
2Iowa State University 4Pratt & Whitney Center for NDE 400 Main Street Ames, IA 50011 East Hartford, CT 06108
3General Electric Aircraft Engines 1Honeywell Engines, Systems & Services Cincinnati, Ohio 111 S. 34th Street Phoenix, Arizona 85072
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Contract or Grant No.
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Type of Report and Period Covered
Final Report
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Sponsoring Agency Name and Address
U.S. Department of Transportation Federal Aviation Administration Office of Aviation Research Washington, DC 20591
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Sponsoring Agency Code
ANE-100
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Supplementary Notes The FAA William J. Hughes Technical Center Technical Monitors were Rick Micklos, Paul Swindell, and Cu Nguyen. 16. Abstract
High-speed bolthole (HSBH) eddy-current inspection is the most popular inspection technique for fast and accurate inspection of circular air- and boltholes. When HSBH techniques were introduced in the field, inspection differences among original equipment manufacturer (OEM) techniques were unclear. Also unavailable were quantification of inspection capability and identification of the main sources of variation for this inspection technique. A three-factor, two-level design of experiment was conducted to determine the main sources of variations to better control the inspection process. A semiautomated scanner prototype was designed and manufactured to minimize these variations. The scanner and associated fixturing were then tested to compare the process capability and reliability with that of the typical manual field technique. Both approaches were found to exceed the program performance metric of detecting a 30-mil crack with 4:1 signal-to-noise ratio in a common bolthole geometry. The semiautomated scanner showed a 30% improvement in the 90% probability of detection point with 95% confidence (12-mil crack) compared to a manual inspection (17-mil crack) using experienced eddy-current inspectors and relatively short 0.25″ long bolthole crack specimens. Scanner reliability testing resulted in a written inspection technique that was jointly used by the OEMs and served to further improve the inspection. Information gained in the process of improving this inspection was used to make recommendations for possible modification of the industry specification, SAE AS4787, “Eddy Current Inspection of Circular Holes in Nonferrous Metallic Hole Inspection in Aircraft Engines.”
www.tc.faa.gov/its/worldpac/techrpt/ar05-34.pdf