Investigation and Remediation of a Complex Failure of a High Strength Steel Fan Midshaft from a GEnx Engine
Erik M Mueller, Chair of the FAS International Relations Committee for ASM International
On July 28, 2012, a Boeing 787-8 airplane experienced a loss of thrust in the right GEnx turbofan engine during a pre-flight, low speed taxi test at Charleston International Airport in Charleston, South Carolina. Inspection of the engine revealed the forward end of the fan midshaft had separated, causing the low-pressure turbine rotor to shift aft, damaging that section of the engine. A detailed investigation found the fan midshaft on the GEnx engine had separated from an environmentally assisted cracking mechanism under static load. Cracking was predicated by an intricate and previously undetected reaction between the fan midshaft ultra-high strength steel, the dry film lubricant, and the assembly aid. This investigation explored multiple and fundamental aspects of the fan midshaft, including manufacturing, assembly, design, and loading. From the investigation, a non-destructive inspection was developed and employed throughout the fleet with multiple changes to the assembly of the GEnx engine to prevent future reoccurrences.
Dr. Erik Mueller is currently a Materials Research Engineer in Washington, DC. He had performed over 100 failure investigations of aircraft, rail, pipeline, and marine transportation accidents. In 2018, Erik won the John K. Lauber Award from his agency for his work on the Centreville pipeline accident, and he received the Silver Medal award for his contributions to failure analysis and ASM International. In addition, he recently won the Journal of Failure Analysis and Prevention 2018 Best Paper Award. He is a licensed professional engineer in Florida, Virginia and the District of Columbia. Dr. Mueller graduated from the University of Florida in 2007, served as the official mascot (Albert the Alligator). Erik has served on the Board of Directors for the Failure Analysis Society, has been an editor of ASM Handbook Volumes 3 and 10, volunteers with the ASM Women in Engineering Committee, teaches failure analysis to high school students at the Eisenmann Materials Camp each summer, while also teaching the PE test prep course for TMS.