On September 21, 1995, at 1735 Alaska daylight time, a wheel equipped Piper PA-28-181 airplane, N38293, registered to and operated by L.A.B. Flying Service of Juneau, Alaska, experienced an in-flight separation of 4.5 to 5 inches of a propeller blade tip during climbout from Gustavus, Alaska. The mail flight, operating under 14 CFR Part 135, was departing Gustavus on a company visual flight rules flight plan and the destination was Juneau, Alaska. The commercial certificated pilot, the sole occupant, was not injured and there was no damage to the airplane. According to the pilot, he was on climbout after taking off from Gustavus when the engine and airplane began to shake. He reduced the power to 1300 RPM and returned to Gustavus without further incident. Ground examination of the airplane's propeller showed that approximately 4.5 to 5 inches of one propeller blade had separated. The separated portion of the blade was not recovered. The propeller was submitted to the NTSB Materials Laboratory Division for metallurgical examination. The examination showed that about 60 percent of the blade cross section contained fracture features indicative of fatigue cracking. The fatigue cracking emanated from an origin area located on the leading edge of the blade. The origin area contained a nick. The entire length of the nick could not be determined because the separated piece was not recovered. However, measurements showed that the portion of the nick on the propeller blade was approximately 0.35 inch long. A sectioned piece of the propeller blade was tested for hardness and material composition, and was found to meet the design specifications.