The JT8D 1st stage turbine blade has had in-service challenges for some time. This has primarily been attributed to multiple failure mechanisms, which often intertwine to produce unscheduled engine removals, in-flight shut downs, and failures. The main contributors are intergranular attack, overtemps, thin walls, core shifts and cracking. Since most inspection techniques only detect cracking, or measure dimensions (thin wall), a significant number of “bad” blades were still escaping the inspection process. Delta engineering desired a better inspection technique to determine the serviceability of each of these conditions.
PCRT provided a quick, easy method for determining the structural acceptability of the blade allowing Delta to reject only blades with defects, avoiding the costly wholesale blade replacement with new parts. This resulted in significant savings by not throwing away “good” parts, and will likely increase reliability of the JT8D engine by removing the “bad” blades.