What was found
THE PILOT AND CO-PILOT WERE THE ONLY 2 PERSONS ONBOARD THE ACFT DURING A TRAINING FLIGHT. AT APPROX 11,000`, PA AND 110 KIAS THE PILOTS NOTICED AN UNUSUAL VIBRATION AND ELECTED TO MAKE A PRECAUTIONARY LANDING. POST FLIGHT INSP BY A MX REVEALED DELAMINATION BETWEEN THE BLADE SKIN AND HONEYCOMB ON THE BOTTOM OF 1 BLADE, APPROX 10 IN, WIDE BY 3.5 FEET LONG. THE DELAMINATION WAS MID-SPAN AND MID-CORD.