NTSB Factual Report

On May 28, 2007, at 0725 Pacific daylight time, a Cessna TU206G, N7395C, experienced a loss of engine power during cruise flight, made a forced landing, and came to rest inverted in a salt marsh 3.5 miles southwest of Napa County Airport (APC), Napa, California. The pilot/owner operated the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91 as a personal cross-country flight. The airplane sustained substantial damage. The pilot and one passenger were not injured; another passenger sustained minor injuries. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight was destined for the Shelter Cove Airport (0Q5), Shelter Cove, California.

According to the pilot, the flight departed Buchanan Airport (CCR), Concord, California, about 0710. About 10 minutes later, the pilot noted a loss of engine power with a rough running engine. The pilot contacted CCR tower, and reported the situation to the controller. He then attempted to contact Travis Air Force Base controllers. The pilot stated that he heard a very loud noise coming from the engine, along with significant vibrations. The airplane was losing altitude, and the pilot did not think he would be able to make it to the airport, and decided to make a forced landing in the salt marsh area. On the landing rollout, the landing gear dug into the ground, and the airplane came to rest inverted.

The pilot was interviewed by a responding deputy from the Napa County Sheriff's Department. The pilot stated that there were no problems with the engine during the climb out. When he looked at the instrument panel, he noted a fluctuation in power, and turned off his radio so that he could listen to the engine. The pilot reported that the "power was falling off as if he had lost his turbocharger." He felt a heavy vibration emanate from the airplane, and then the engine lost total power.

AIRCRAFT INFORMATION

A review of the airplane logbooks revealed that an annual inspection had been completed on March 18, 2007, at a tachometer time of 5,259.0 hours. A Teledyne Continental Motors TSIO-520-M6B, serial number 818045-R engine was installed on the airplane; the mechanic recorded the tachometer time as 5,259.6 hours.

A Federal Aviation Administration (FAA) aviation safety inspector from the Sacramento, California, Flight Standards District Office (FSDO) interviewed the airframe and power plant mechanic that had recently worked on the airplane (4 days prior to the accident). The mechanic stated that he had replaced the vacuum pump, and it had taken him about 6 hours to accomplish the task. The mechanic reported that he did not document the maintenance performed in the aircraft maintenance records because he did not possess the airplane's logbooks. He also stated that he did not notify the owner of the airplane that the work had not been documented. The FAA inspector asked what associated components that the mechanic disturbed when he replaced the vacuum pump. The mechanic indicated that he disturbed the upper duct elbow at the throttle body and a turbocharger component that controls the waste gate associated with the turbocharger.

After the accident, the mechanic mailed to the pilot's insurance adjuster the entry he would have entered into the aircraft logbook had it been available to him. The sign off stated in part:

"May 24, 2007, TACH 5274.0 Removed defective Airborne vacuum pump 216CW and installed Rapcoo 216 CW vacuum pump S/N B15162."

TESTS AND RESEARCH

An airframe and engine inspection took place at Plain Parts, Pleasant Grove, California, on June 26, 2007. The visual inspection of the airframe revealed no traces of oil residue or other obvious mechanical anomalies. A visual inspection of the engine revealed a circular crack at the number 5 cylinder, and red discoloration of the top portion of the cylinder fins. Investigators were not able to manually rotate the engine. The spark plugs were removed, with the number 4 top and bottom plugs heavily sooted; the other spark plugs appeared normal according to the Champion Aviation check-a-plug chart. Investigators disassembled the engine, and noted that the number 5 connecting rod had separated from the crankshaft, with portions of the connecting rod arm located in the oil sump. The number 2 main bearing exhibited wear to the copper layer with dark coloration. Material from the main bearing blocked one of the oil passage holes of the number 2 main bearing. The other main bearings exhibited moderate to light wear with discoloration. The number 5 main bearing was normal in appearance. High pressure air source was utilized to check for blockage of the oil galleys and passages. No blockage was noted, except for the number 5 crankshaft rod journal oil port that was obstructed by smeared metal. The numbers 1-4, and 6 connecting rods showed thermal discoloration. Approximately 2 to 3 quarts of oil was drained from the oil sump, along with portions of the number 5 connecting rod, pieces of piston and piston rings, and the intake and exhaust lifters for the number 5 cylinder. Metallic particles were observed on the oil filter, and the exhaust stack also showed thermal discoloration. Investigators noted that the exterior of the turbocharger was oil soaked. The line to the turbocharger was finger tight; however, the connecting arm was loose.

NTSB Probable Cause

Failure of the number 5 connecting rod due to oil starvation.