Question 16Gas Turbine - 1st Asst/Chief

The correct answer is D) Failure of a rotor bearing. Once a compressor is broken in, a failure of a rotor bearing is the factor that is most likely to cause the blade tips to rub. This is because a failed rotor bearing can lead to shaft misalignment, which in turn can cause the blade tips to come into contact with the stator case, resulting in rubbing and potential damage. The other answer choices are not as directly related to the blade tip rubbing issue. Sprayed material in the stator case, elongation of the blade tips, or profiles on the blade tips may contribute to compressor issues, but they are not the primary cause of blade tip rubbing after the initial break-in period.