Southwest Research Institute® wins FAA grant for turbine safety program

The probabilistic-based software code for turbine engine rotor design and life management, called "Design Assessment of Reliability with Inspection," was developed at SwRI under the program's initial phase which began in 1995.

The FAA's public release of the code is marked by a training session for industry and government users, scheduled May 17-19 at SwRI.

"This design tool will increase the safety of the commercial airliner fleet," said Dr. Gerald Leverant, manager of the FAA program and program director for Power Generation Materials in SwRI's Mechanical and Materials Engineering Division. "For new designs, it is anticipated that the rate of uncontained titanium disk failures due to melt-related defects will be decreased by a factor of at least three," he added.

An uncontained failure, in which a rapidly spinning turbine engine rotor disk flies apart and its pieces escape the engine casing, can damage other aircraft systems and cause a crash. Investigators identified such a failure as the cause of a 1989 fatal accident involving a DC-10 airliner at Sioux City, Iowa.

The release of the tool supports a National Transportation Safety Board recommendation. While current engine rotor design and life methods historically have served the industry well, the new code enhances these methods by explicitly addressing embedded melt-related defects, which are exceptionally difficult to find using current nondestructive inspection methods.

The computer code predicts the risk of uncontained failures due to "hard alpha defects," or flaws created when the raw titanium into the disk, was melted and forged, Leverant said. The code, which runs on a workstation, incorporates sophisticated risk assessment methods into design procedures so that risk of failure is minimized and inspections can be scheduled realistically.

Under the program's second phase, Institute scientists and engineers will enhance the probabilistic code to predict the risk associated with inherent defects not only in titanium turbine disks, but also those made of nickel. The code will also be modified to predict the risk associated with manufacturing- and maintenance-induced surface flaws in all disk materials, including nickel and steel as well as titanium.

Four major U.S. jet engine manufacturers -- AlliedSignal, Rolls Royce-Allison, General Electric, and Pratt & Whitney -- are subcontractors on the program. In addition, SwRI reports results to an international aviation industry committee, called the Rotor Integrity Subcommittee of the Aerospace Industries Association, which is comprised of U.S. and foreign gas turbine manufacturers.

SwRI is an independent, nonprofit, applied engineering and physical sciences research and development organization with a staff of 2,700 and an annual research volume of $304 million.

For more information about the turbine safety program, contact Joe Fohn, Communications Department, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas, 78228-0510, Phone (210) 522-4630, Fax (210) 522-3547.

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