Accident Overview
On November 11, 2013, at approximately 0830 eastern standard time, a Piper PA-28-140, registration N1830T, operated by a private individual, was substantially damaged during a forced landing near Homestead, Florida. The student pilot, who was the sole occupant, was not injured. The flight was conducted under 14 Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed, and a visual flight rules flight plan had been filed.
The flight departed Key West International Airport, Key West, Florida, destined for Sarasota-Bradenton International Airport, Sarasota, Florida. While at an altitude of 5,500 feet mean sea level, the student pilot felt a slight engine vibration. All engine gauges remained normal, but the vibration increased, prompting a diversion to Homestead General Aviation Airport. Shortly thereafter, the engine "began coming apart," with pieces striking the underside of the cowling. The student pilot performed a forced landing to Everglades National Park, where the airplane came to rest in shallow water, resulting in substantial fuselage damage.
Engine Examination
The airplane was equipped with a Lycoming O-360-A1A, 180-horsepower engine. An initial examination 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 one year later and 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, including two cylinder studs, was missing. The No. 3 cylinder connecting rod remained attached to the crankshaft and moved freely, but its piston pin portion was fractured. The crankcase and No. 3 connecting rod were forwarded to the NTSB Materials Laboratory for further examination.
Metallurgical Findings
An NTSB metallurgist examined the retained engine parts. 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 on 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, consistent with a room-temperature-vulcanizing (RTV) material. According to the applicable Lycoming engine overhaul manual, the parting surfaces were to be sealed by applying a film of non-hardening gasket compound and embedding a length of "00" silk thread into the gasket material. Lycoming Service Instruction 1125D, dated October 17, 2008, approved two alternate sealant materials, which were white and dark purple.
Maintenance History
According to maintenance records, the engine was overhauled and installed on the accident airplane on March 15, 1985. Available records did not indicate any in-service cylinder replacements or reinstallations. At the time of the accident, the engine had accumulated about 1,050 total hours since overhaul and about 230 hours since its most recent annual inspection, which was performed on March 1, 2013.