What was found
ON DESCENT, HEARD SOUND SIMILAR TO WHISTLE & HEARD SOUNDS DURING RT BANK ON APPR. A/C SHUTDOWN, INSP M/R BLADES & STAB BAR FOR CAUSE OF NOISE. SUSPECT BLADE TAPE ON STAB BAR LOOSE. NO DEFECTS FOUND. NO FURTHER NOISE APPARENT. APPROX 1-2 MINS INTO NEXT FLT, A/C RETURNED, VIBE LEVEL INCREASED WITH FEEDBACK THROUGH CONTROLS & AIRFRAME OF VERT. DIFFERENT NOISE WITH INCREASED VOLUME HEARD DURING APPR. A/C LANDED, SHUTDOWN, REPORTED INCREASE VERT VIBE LEVEL IN A/C WITH VIBE IN CONTROLS DECIDED TO RETURN & SHUTDOWN. INSP REVEALED UPPER SKIN NEAR OUTBOARD TIP HAD LIFTED AFT ABRASION STRIP. AREA AFFECTED APPROX 4 INCHES BY 2 INCHES. ADHESIVE SEPARATED CLEANLY. NO VISIBLE CORROSION OR AUDIBLE DELAMINATION.