DFW08LA094

The private pilot/owner and the passenger were on a cross country flight at an altitude of 6,500 feet when a section of propeller blade broke off and the airplane began to shake violently. The pilot reduced power, slowed the airplane and stalled the propeller, which reduced the vibrations. He then declared an emergency and made a forced landing to a field. Examination of the airplane revealed that approximately 44-inches of one of the Sensenich fixed-pitch (all metal) propeller blades had separated and was not recovered. The other blade was intact. The top and bottom engine mounts on the right side (as viewed from the cockpit) were severed and the engine was displaced down and to the right. A materials examination of the propeller's fractured surface revealed fatigue cracking through approximately 85 percent of the blade and corrosion pitting at the initiation point of the failure. The remaining portion of the fracture was more jagged, had a matte appearance, and was oriented at a slant angle, which was indicative of a final overstress fracture region. A review of Sensenich's records revealed that in April 1991, this propeller (which was original to the airplane) was sent to Sensenich to be reworked; however, it was rejected due to the fact that it was "out of material chord at the tip." The propeller was returned, and at some point was placed back on the airplane. However, there was no logged entry in the airframe logbook that indicated when this was accomplished or by whom. On June 13, 1996, the FAA issued Airworthiness Directive (AD) 69-09-03, Revision 3, titled, Sensenich Propeller Manufacturing Company Incorporated models M76EMM, M76EMMS, 76EM8, and 76EM8S metal propellers. The directive was issued, "To prevent propeller blade tip fatigue failure, which can result in loss of control of the aircraft..." As a result, this particular propeller was to be removed, inspected, and reworked in accordance with Senseinich Propeller Service Bulletin (SB) number R-14A, dated July 28, 1995. Those propellers that had been inspected in accordance to the Service Bulletin and found satisfactory were to be marked with the suffix letter "K." Examination of the accident propeller revealed there was no "K" marking. In addition, a review of the logbooks revealed that the AD had not been complied with as required per Federal Aviation Regulations.

On April 7, 2008, approximately 1450 central daylight time, a single-engine Piper PA-28-180, N5300L, sustained substantial damage after a section of propeller blade separated in cruise flight which resulted in a forced landing to a wheat field near Paducah, Texas. The certified private pilot and the passenger were not injured. The airplane was registered to and operated by the pilot. No flight plan was filed for the flight that departed Clark Field Municipal Airport (SEP), Stephenville, Texas, about 1300, and was destined for Moore County Airport (DUX), Dumas, Texas. Visual meteorological conditions prevailed for the business flight conducted under 14 Code of Federal Regulations Part 91.

In a written statement, the pilot said that he was in cruise flight at an altitude of 6,500 feet about 15 miles south of Childress, Texas, when the propeller broke off with a "bang" followed by "extremely violent shaking as if the engine was going to fall off." The pilot then reduced power, slowed the airplane and stalled the propeller, which reduced the vibrations. He then declared an emergency and made a forced landing to a field.

The airplane was recovered to a salvage facility where it was examined by the Safety Board Investigator-in-Charge (IIC). Examination of the airplane revealed that approximately 44-inches of one of the Sensenich fixed-pitch (all metal) propeller blades had separated and was not recovered. The other blade was intact. The top and bottom engine mounts on the right side (as viewed from the cockpit) were severed and the engine was displaced down and to the right. In addition, the lower right hand side of the Plexiglas windshield had pulled away from the fuselage and there were some wrinkles to the fuselage in the vicinity of the windshield damage.

The fractured propeller blade (model M76EMMS, serial number 44624) was examined on April 16, 2008, at the Safety Board's Materials Laboratory in Washington, DC. Examination of the fractured surface revealed two distinct areas. According to the Materials Laboratory Factual Report, one area "... was relatively flat, was approximately on a chordwise plane, and had a reflective appearance with crack arrest positions, all typical of fatigue cracking. This area extended through approximately 85 percent of the blade cross section at the fracture location. The crack arrest fronts lead to a crack initiation point on the camber side of the blade, 2.6 inches from the leading edge. Stripping of the paint from the exterior surface of the blade in the area of the initiation point revealed evidence of small corrosion pits associated with the origin area. The corrosion pit indicated in was about 0.004 inch wide. The remaining portion of the fracture was more jagged, had a matte appearance, and was oriented at a slant angle, all features indicative of a final overstress fracture region."

A review of Sensenich's records revealed that in April 1991, the accident propeller (which was original to the airplane) was sent to Sensenich to be reworked; however, it was rejected due to the fact that it was "out of material chord at the tip." The propeller was returned to the previous owner, and at some point was placed back on the airplane. However, there was no entry in the airframe logbook that indicated when this was accomplished or by whom.

On June 13, 1996, the Federal Aviation Administration (FAA) issued Airworthiness Directive (AD) 69-09-03, Revision 3, titled, Sensenich Propeller Manufacturing Company Incorporated models M76EMM, M76EMMS, 76EM8, and 76EM8S metal propellers. The directive was issued, "To prevent propeller blade tip fatigue failure, which can result in loss of control of the aircraft..." As a result, the accident propeller was to be removed, inspected, and reworked in accordance with Sensenich Propeller Service Bulletin number R-14A, dated July 28, 1995. If the propeller had been inspected in accordance to the Service Bulletin and found satisfactory it was supposed to be marked with the suffix letter "K." Examination of the accident propeller revealed there was no "K" marking. In addition, a review of the airframe logbook revealed that the AD had not been complied with as required per Federal Aviation Regulations.

The pilot held a private pilot certificate for airplane single engine land. His last second class FAA medical was issued in May 2007. The pilot reported a total of 257 flight hours, of which, 219 hours were in the same make and model of the accident airplane.

Weather at Childress Municipal Airport (CDS), Childress, Texas, about 16 miles northwest of the accident site, at 1353, was reported as wind from 170 degrees at 6 knots, 10 miles visibility, and clear skies.