ATL94LA169

While in cruise flight, the engine oil pressure decreased and the oil temperature increased. The engine lost power rapidly, and quit. A forced landing was made to a four lane highway. The pilot said he maneuvered the airplane to avoid a collision with electrical power lines and vehicles. The landing gear was not extended to avoid catching on power lines. After touchdown on the highway, a vehicle backed into the road and was struck by the right wing tip. Post accident examination of the engine revealed that the number 2 piston exhibited signs of pre-ignition /detonation, I.e. a hole was burned in the piston. Testing of the engine fuel system demonstrated that it was capable of providing required fuel to the engine. The pilot reported that the airplane was full of 100LL fuel when the flight departed. Excessive fuel leaning, during improper usage of the mixture control, will result in engine detonation.

On September 8, 1994, at 1015 eastern daylight time, a Cessna T210M, N761GQ, collided with an automobile while attempting a forced landing on a state highway near Willacooche, Georgia. The business flight operated under the provisions of 14 CFR Part 91, with no flight plan filed. Visual weather conditions prevailed at the time of the accident. The were no injuries to the private pilot, nor the passenger, and the airplane was substantially damaged. The flight departed Brunswick, Georgia, at 0930 on the same day.

According to the pilot, while in cruise flight, the engine lost oil pressure, the oil temperature was "up," and the engine lost power, rapidly. The pilot selected a four lane highway as a forced landing site. He stated that he maneuvered the airplane to avoid colliding with power lines and vehicles, and left the landing gear retracted to avoid catching the gear on the wires. During the landing roll, the right wing collided with an automobile that was backing out of a driveway onto the highway.

A post accident disassembly of the engine, serial number 513716, was conducted, under the supervision of the Manufacturing Aviation Safety Inspector, at the manufacturer's Mobile, Alabama, facility. The number two piston, Superior Airport part number SA646303, had evidence of pre-ignition/detonation. A hole was burned in the piston crown and the cylinder barrel was scuffed and scored. There was evidence, scratching and polishing, of hard particle passage through the oil pump. Additionally, there was lubrication and thermal distress to the number four and five connecting rod bearings and their respective crankshaft journals.

The fuel pump, manifold valve, and nozzles were tested and found capable of providing sufficient fuel to the engine. The engine examination report stated that one unknown variable was the pilot's use of the mixture control.