History of Flight
On June 24, 2012, about 1155 eastern daylight time, a Universal Stinson 108, registration N39443, operated by a private pilot, was substantially damaged while ditching in the Atlantic Ocean following a total loss of engine power during cruise flight near Portland, Maine. The private pilot was fatally injured. The personal flight was conducted under 14 CFR Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight that departed Twitchell Airport (3B5), Turner, Maine, about 1030.
According to Federal Aviation Administration (FAA) data, the airplane was in radio and radar contact with Portland International Jetport (PWM) Approach Control. The airplane was flying along the coast near PWM at 500 to 1,000 feet mean sea level (msl), south to north. The pilot radioed that his intentions were to fly low for sightseeing and photography. At 1154, the pilot reported a total loss of engine power; at that time the airplane was about 500 feet msl, and the pilot indicated he could not glide to shore. The last radar target was recorded at 11:55:20 at 200 feet msl.
An FAA inspector reported that the airplane impacted water approximately 100 yards from shore and sank to a depth of about 70 feet. The pilot exited and donned a lifevest dropped from a nearby helicopter, but could not inflate it. A boater retrieved the pilot, who was unresponsive.
Personnel Information
The pilot, age 60, held a private pilot certificate with a rating for airplane single-engine land. His most recent FAA third-class medical certificate was issued on November 11, 2010, at which time he reported 504 total flight hours. His logbook was not recovered.
Aircraft Information
The four-seat, high-wing, fixed-gear tailwheel airplane, serial number 108-13, was manufactured in 1946. It was equipped with a Franklin 6A4-150-B31, 150-horsepower engine, serial number 13762. The pilot owned and operated the airplane. According to aircraft logbooks, the most recent annual inspection was completed on November 4, 2011, at 2,114.5 total aircraft hours. The engine had 1,727.5 total hours and 7.5 hours since major overhaul (completed February 9, 2007). The engine was initially installed on August 1, 1947, with 100 total hours since new. The airplane had flown approximately 10 hours since the last annual inspection.
Wreckage and Impact Information
An FAA inspector noted a sheen of fuel on the ocean surface when the airplane was recovered. After recovery, flight control continuity was confirmed. The airplane was not equipped with shoulder harnesses. The propeller could be rotated by hand, confirming crankshaft, camshaft, and valve train continuity to the rear accessory section. Partial disassembly of the engine revealed that the No. 3 piston skirt had fractured. Pieces from the skirt entered the engine, including into the camshaft gear, affecting magneto timing.
During a telephone interview, the mechanic who overhauled the pistons in 2007 stated he was not surprised one failed, as they were 60 to 70 years old. The mechanic balanced the six pistons by ensuring equal weight using a precision gram scale. He removed weight from the balance band (approximately 1/8 inch wide and 3/16 inch deep, located behind the piston skirt about 1 inch from the oil port) by grinding until desired weight was achieved.
The No. 3 piston was sent to the NTSB Materials Laboratory. Metallurgical examination revealed two fracture surfaces on the piston skirt, smeared with mechanical contact. The first surface smearing precluded determining fracture mode. The second surface was less smeared and exhibited characteristics consistent with fatigue originating near a machined through-hole, not in the vicinity of the piston balance band.
Medical and Pathological Information
An autopsy performed on June 26, 2012, by the State of Maine Medical Examiner’s Office noted the cause of death as blunt force injuries of neck and chest with hypothermia and submersion. Toxicological testing by the FAA Bioaeronautical Science Research Laboratory detected dextromethorphan in the liver and femoral blood.