On July 16, 1997, at 1150 hours Hawaiian standard time, a Classic Aircraft Corporation Waco YMF-5, N553T, sustained an in-flight separation of the propeller during cruise flight near the Pu`u `O`o volcanic crater and made a forced landing in a lava field close to Pahoa, Hawaii. The aircraft was owned by Classic Aircraft Corporation and was operated on a 14 CFR Part 91 local area for-hire sightseeing flight. The aircraft incurred substantial damage. The commercial pilot and one passenger were not injured, however, the remaining passenger received minor injuries. Visual meteorological conditions prevailed at the time of the accident. The pilot reported in a verbal statement to Federal Aviation Administration (FAA) inspectors that there was no unusual vibration or other warning prior to the propeller separating from the aircraft. In his written statement, the pilot further reported that he personally inspected the propeller, retaining nut, and clevis pin the morning of the accident. Two prior flights were successfully completed, and the accident occurred on the third flight of the day. During the aircraft recovery efforts, the propeller was found over a mile from the aircraft point of rest. Propeller hub/attachment components consisting of the forward cone, a snap ring, the hub retaining nut, and the clevis pin were not located. An examination of the aircraft was conducted by FAA Airworthiness inspectors from the Honolulu Flight Standards District Office following recovery of the wreckage. The inspectors reported that "nothing unusual" was noted to the crankshaft splines, threaded front end (where the retaining nut is installed), or the grooves for the clevis pin. The examining inspectors stated that, "apart from impact damage there was no other evident damage to propeller shaft that would suggest premature failure of propeller shaft that would cause departure of propeller from aircraft." The only specific discrepancy the FAA inspectors found was that the propeller on the aircraft was not the one listed in the maintenance records as being installed on the aircraft. According to the maintenance records, propeller serial number AC0217 was supposed to be the one installed at the time of the accident. Serial number AC9806 was stamped on the propeller recovered from the accident scene.