NTSB Factual Report

On November 11, 2013, about 0830 eastern standard time, a Piper PA-28-140, N1830T, operated by a private individual, was substantially damaged during a forced landing, after it experienced a total loss of engine power while in cruise flight near Homestead, Florida. The student pilot was not injured. Visual meteorological conditions prevailed and a visual flight rules flight plan had been filed for the flight that departed Key West International Airport, Key West, Florida, destined for the Sarasota-Bradenton International Airport, Sarasota, Florida. The instructional flight was conducted under the provisions of 14 Code of Federal Regulations Part 91.

The student pilot owned and operated the airplane. He reported that the airplane was at an altitude of 5,500 feet mean sea level, when he felt a slight engine vibration. All engine gauges remained normal; however, the vibration began to increase and the student pilot elected to divert to the Homestead General Aviation Airport, Homestead, Florida. Shortly thereafter, the engine "began coming apart" with pieces striking the underside of the cowling. The student pilot subsequently performed a forced landing to Everglades National Park. The airplane came to rest in shallow water and sustained substantial fuselage damage.

The airplane was equipped with a Lycoming O-360-A1A, 180-horsepower engine. Initial examination of the airplane by a Federal Aviation Administration inspector revealed that the No. 3 cylinder had separated from the crankcase. The airplane was recovered from the accident site about 1 year after the accident and subsequently examined by an NTSB investigator. The crankshaft and valve train were seized and could not be rotated by hand. A large breach in the crankcase was noted above the No. 3 cylinder mount pad, and the upper portion of the mount pad, which included two cylinder studs, was missing. The No. 3 cylinder connecting rod remained attached to the crankshaft and moved freely. The piston pin portion of the No. 3 cylinder connecting rod was fractured. The crankcase and No. 3 connecting rod were forwarded to the NTSB Materials Laboratory, Washington, DC for further examination.

Examination of the retained engine parts by an NTSB metallurgist revealed that in addition to the crankcase fracture at the No. 3 cylinder attachment area, both through bolts, and three of the four remaining cylinder studs were fractured. The crankcase and No. 3 connecting rod fractures were typical of overstress separations; however, the three cylinder studs, and two through bolts contained fractures consistent with fatigue fractures. Light fretting wear scars were noted on the main bearing boss surfaces between the forward and aft cylinders, and the bearing bosses at the forward through bolts. Light fretting wear was also noted adjacent to the middle bearing boss for the camshaft.

The outer surfaces of the parting crankcase halves displayed thin reddish sealant material. The material appeared consistent with a room-temperature-vulcanizing (RTV) material. According to the applicable Lycoming engine overhaul manual, the parting surfaces of the crankcase halves were to be sealed by applying "a film of non-hardening gasket compound" to certain surfaces and imbedding a length of "00" silk thread into the gasket material on one side of the case. Lycoming Service Instruction 1125D, dated October 17, 2008, provided instructions for "Alternate Crankcase Parting Surface Sealant," and identified two approved alternate sealant materials, which were white and dark purple in color. [Additional information can be found in Materials Laboratory Factual Report No. 15-057 located in the public docket.]

According to maintenance records, the engine was overhauled and installed on the accident airplane on March 15, 1985. Available maintenance records did not reveal any in service cylinder replacements or reinstallations. At the time of the accident, the engine had been operated for about 1,050 total hours since overhaul, and about 230 hours since its most recent annual inspection, which was performed on March 1, 2013.

NTSB Probable Cause

A total loss of engine power due to the in-flight separation of the No. 3 cylinder because of the fatigue cracking of its respective mounting studs and through bolts, which resulted from inadequate maintenance by unknown personnel.