Accident Details
On April 1, 2012, at approximately 1515 central daylight time, a Cessna U206B airplane, registration N3830G, lost engine power shortly after departing from Winterset Municipal Airport (3Y3) in Winterset, Iowa. The commercial rated pilot and six passengers were not injured, but the airplane sustained substantial damage. The aircraft was registered to and operated by Des Moines Skydivers, LLC, of Des Moines, Iowa, under 14 Code of Federal Regulations Part 91 as a parachute jump flight. Day visual meteorological conditions prevailed, and no flight plan was filed.
Pilot Account
The pilot reported that after departure on a jump flight, he turned crosswind and headed north. At about 1,000 feet above ground level, the airplane seemed to stop climbing. The pilot checked the engine gauges, which appeared normal, but then the engine analyzer flashed “CHT” and indicated a cylinder temperature of 454 degrees Fahrenheit. The pilot pitched the nose down to cool the engine and turned back toward the airfield. He then heard a muffled “thud” and saw white smoke pouring from the engine. He pulled the mixture control, turned off the ignition and master switches, and yelled for the jumpers to exit. Four parachutists were able to leave the airplane. The pilot performed a forced landing in a plowed field, and the airplane came to a stop near a dirt berm.
Damage and Inspection
The responding Federal Aviation Administration (FAA) inspector reported that the airplane sustained extensive firewall damage when the nose landing gear was torn off during the forced landing. A hole was noted in the engine’s crankcase near the number four cylinder.
Engine Examination
The engine was removed from the airframe and sent to Continental Motor’s engine test facility in Mobile, Alabama. Examination occurred under the supervision of the NTSB Investigator in Charge and technical representatives from Continental Motors. Visual inspection confirmed the hole in the crankcase near the number four cylinder. The engine was disassembled, revealing various pieces of metal, including part of a “quick oil drain plug,” in the oil sump. The number four connecting rod journal appeared distorted and exhibited extensive heat signatures. The crankshaft journals on either side of the number four rod journal showed no distortion or similar heat signatures and were coated with engine oil. The rod and crankshaft bearings appeared scored. The crankcase and crankshaft oil galleys appeared open. No reason for the loss of engine oil to the journal was found.
Maintenance Records
A review of the engine maintenance log book revealed that the engine had approximately 3,233 total hours and about 1,730 hours since major overhaul.