Two compressor rotors of similar design and construction were severely damaged during operation. In one rotor, all the blades in the third and fourth stages had been sheared off and some had lifted from the dovetail portion of the drum. The damage in the other rotor was more extensive. Most of the blades in the first four stages had sheared off and many lifted from the dovetail region, particularly in the first two stages where several mounting dovetails had also fractured. Based on visual examination and the results of SEM fractography, metallography, and chemical analysis, investigators concluded that the compressor rotors failed due to stress-corrosion cracking in the dovetail mountings. They also provided recommendations to prevent or mitigate future occurrences.

A titanium alloy disc on the fourth stage of an aircraft engine compressor was found cracked in the course of a defect investigation. The disc had not yet reached the halfway point of its expected service life. The chapter explains how the crack was examined and provides relevant details about its location on the disc and various aspects of its appearance. It also explains how failure analysts concluded that the disc had been subjected to a fluctuating load of high magnitude and that the crack was the result of two fatigue cracks, originating from opposite sides of the diaphragm.