Narrative:

While conducting pre-start walk around noticed a dent centered in a single tail rotor paddle approximately halfway in distance between the root and end of the blade. Here is the sequence of events. I conducted a pre-flight of the aircraft in the morning upon reporting for my shift with no aircraft deficiencies noted. [I] received an inter-hospital flight request for a patient pick-up at hospital for transport to another hospital. Conducted pre-start walk around with no deficiencies noted and flew to the sending hospital. After shutdown; [I] conducted post-flight walk around with no deficiencies noted. Loaded patient; conducted pre-start walk around with no deficiencies noted and flew to receiving hospital. After shutdown at receiving hospital; conducted post-flight walk around with no deficiencies noted and serviced the helicopter. Conducted crew link up inside the hospital and moved back outside for departure back to base. During the execution of my pre-start walk around prior to returning to base; noted a shadow on one of the tail rotor paddles that 'didn't look right.' upon close-up visual examination and moving the blades to just the right position in relation to the sun; noted a dent in the paddle that; when touched; felt to me as a delamination in the fiberglass outer shell from the inner foam core of the paddle itself. After grounding the aircraft; I contacted the base mechanic to initiate the logistical requirements of repairing the tail rotor and contacted our communications center to take us out of service. If something does not look right; feel right or smell right; stop; assess the situation; and determine a course of action. On this day; I personally looked at the tail rotor on five separate occasions and did not notice any deficiencies. During the execution of the sixth walk around of the day; the sun was at just the right angle to create a shadow that allowed me to discover what could have been a catastrophic flaw for the tail rotor. (Point of note; one hour later; it took three of us to find the dent again since the sun had moved enough to create a different lighting angle on the blade.)

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Original NASA ASRS Text

Title: A BK117 pilot discovered a possible delamination in one of the tail rotor blades while conducting the sixth walk around of the day. The flaw was very difficult to detect until daylight at the correct angle revealed a shadow which; when examined; revealed the flaw.

Narrative: While conducting pre-start walk around noticed a dent centered in a single tail rotor paddle approximately halfway in distance between the root and end of the blade. Here is the sequence of events. I conducted a pre-flight of the aircraft in the morning upon reporting for my shift with no aircraft deficiencies noted. [I] received an inter-hospital flight request for a patient pick-up at hospital for transport to another hospital. Conducted pre-start walk around with no deficiencies noted and flew to the sending hospital. After shutdown; [I] conducted post-flight walk around with no deficiencies noted. Loaded patient; conducted pre-start walk around with no deficiencies noted and flew to receiving hospital. After shutdown at receiving hospital; conducted post-flight walk around with no deficiencies noted and serviced the helicopter. Conducted crew link up inside the hospital and moved back outside for departure back to base. During the execution of my pre-start walk around prior to returning to base; noted a shadow on one of the tail rotor paddles that 'didn't look right.' Upon close-up visual examination and moving the blades to just the right position in relation to the sun; noted a dent in the paddle that; when touched; felt to me as a delamination in the fiberglass outer shell from the inner foam core of the paddle itself. After grounding the aircraft; I contacted the base mechanic to initiate the logistical requirements of repairing the tail rotor and contacted our communications center to take us out of service. If something does not look right; feel right or smell right; stop; assess the situation; and determine a course of action. On this day; I personally looked at the tail rotor on five separate occasions and did not notice any deficiencies. During the execution of the sixth walk around of the day; the sun was at just the right angle to create a shadow that allowed me to discover what could have been a catastrophic flaw for the tail rotor. (Point of note; one hour later; it took three of us to find the dent again since the sun had moved enough to create a different lighting angle on the blade.)

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.