In turbine engine investigations, which option indicates a High RPM - Low Angle impact in the compressor?

• A. Non-uniform bending
• B. Sh1aft bent, not sheared
• C. Disk failure
• D. Blades tips curled forward (Correct)

Answer: (D)

When a foreign object hits a compressor blade at very high rotational speed and at a shallow, low-angle incidence, the most telling damage is a forward curl of the blade tip. The blade tip is moving extremely fast, so an impact coming in at a small angle tends to bend the tip rather than shear it or break it off cleanly. The impulse pushes the tip in the direction of the rotation, causing plastic deformation that makes the tip curl forward. This forward curling pattern is a distinctive signature of a high RPM, low-angle strike in the compressor.

Other damage patterns don’t align with that specific scenario. Non-uniform bending can result from multiple impacts or uneven loading, not necessarily tied to a high-speed, low-angle event. A shaft bent but not sheared points to rotor or bearing issues rather than a single blade-tip impact. Disk failure involves the disk itself rather than the blade tips. The forward curling of blade tips, however, best matches a high RPM–low angle impact in the compressor.