Cessna P210 N4861P

The pilot was conducting a personal cross-country flight at 2,500 ft mean sea level over the Gulf of Mexico when the airplane had a total loss of electrical power about 1 hour 45 minutes into the flight. The pilot was unable to restore electrical power and he turned toward the shore to land at an airport. He manually extended the landing gear and selected the right-wing fuel tank. A couple minutes later the airplane had a total loss of engine power. The pilot did not switch to the left-wing fuel tank or attempt an engine restart because he was focused on ditching the airplane. The airplane became submerged after the ditching and the right horizontal stabilizer and right elevator were substantially damaged. The airplane was not equipped with a life raft or life preservers. The pilot drifted and swam with the current and tide for over 11 hours until he came ashore an unpopulated barrier island the following morning. The pilot stated that during his preflight inspection the left and right wing tanks contained about 30 gallons and 40 gallons of fuel, respectively. He further estimated that the airplane had at least 68 gallons of useable fuel, about 4 hours of fuel endurance, before he departed on the planned 3-hour flight. He departed using fuel from the right-wing tank and about 1 hour into the flight he switched to the left-wing tank. About 45 minutes later, shortly after the loss of electrical power, he switched to the right-wing tank because it contained the most fuel. The postaccident engine examination revealed no evidence of a mechanical malfunction or failure that would have precluded normal operation. The engine had been submerged in saltwater which prevented an operational test run. Any fuel remaining in the wing fuel tanks was displaced by saltwater after the ditching. However, uncontaminated fuel was found in the fuel strainer and a fuel line between the engine’s fuel manifold and fuel control unit. Although fuel mismanagement could have resulted in a loss of engine power, the investigation was unable to confirm this with the available evidence after the ditching. Examination of the airplane’s electrical system revealed the battery’s positive power cable was loose where it attached to the battery contactor terminal. Additionally, the component stack-up did not include any washers and had a smaller nut when compared to the other cable terminal. The nut had backed off about 2 threads, which resulted in a loose cable connection. The total loss of electrical power during flight was likely due to the loose cable connection on the battery contactor. The engine magnetos produce ignition spark independent of the airplane electrical system; the loss of electrical power did not affect normal engine operation. The reason for the total loss of engine power could not be determined based on available evidence.

Quoted verbatim from the NTSB record.