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On May 28, 2004, at 1330 Pacific daylight time, an experimental, amateur-built Wilson Avid Bandit airplane, N55368, impacted grapevines during a forced landing following a loss of engine power near Paso Robles, California. The private pilot sustained minor injuries and the passenger was not injured. The airplane was substantially damaged. The airplane was registered to, and operated by, the pilot under the provisions of 14 CFR Part 91 as a personal flight. The second leg of the cross-country flight was originating at the time of the accident and was destined for Oceano, California. Visual meteorological conditions prevailed at the time of the accident and a flight plan had not been filed.
During a telephone interview, the pilot stated he was inbound to Paso Robles for landing. During the descent, warmer air was encountered and the liquid-cooled engine began to "act funny." The engine lost power during the descent. The water temperature was indicating 190 degrees Fahrenheit., which was over the red-line limit of 180 degrees Fahrenheit. The pilot successfully restarted the engine and attempted to cool the engine by blowing water over the radiator (a modification added by the pilot, who was the builder of the airplane). The pilot assumed the temperature rise was due to the engine not pumping water during the loss of power. The pilot eventually landed the airplane at Paso Robles.
The pilot, who was the builder of the airplane and its registered repairman, believed he had a fuel system problem and therefore, went through the entire fuel system while on the ground at Paso Robles. He cleaned the fuel filters, drained the system to check for obstructions, disassembled, inspected, and reassembled the fuel pump, and checked the rest of the system. The pilot refueled the airplane (topping off the fuel tanks), checked the tanks for water, checked the radiator water and oil injecting system, and added water to the water spray system. He test ran the engine twice, and after finding no other anomalies and determining his airplane was airworthy, he departed for the second leg of the flight.
The pilot noted that the outside air temperature was between 75 and 80 degrees Fahrenheit. He performed "several" engine run-ups after taxiing to the active runway. The engine appeared to be running in "good order." The airplane departed on the second leg of the flight, and approximately 3 to 4 minutes after takeoff, the engine began overheating. The pilot said the water temperature gauge for the engine began to rise rapidly over the red line. He attempted to cool the engine by lowering the angle of attack, activating the water blower, and turning into the wind, all to no avail. The engine lost total power and the pilot turned back toward the departure airport. The pilot determined they would not make it to the airport and elected to land in a vineyard. During the landing flare, the pilot slowed the airplane, which eventually became snagged by the grapevines. The airplane came to rest inverted.
According to the pilot, the engine had accumulated a total of 557 hours of operation. When it had accumulated a total of 300 hours, it had undergone a complete overhaul and all of its components were replaced with new parts.
The Rotax 582 engine is a 2-stroke, 2-cylinder, in-line engine, which utilizes an integrated water pump and liquid-cooled cylinder heads and cylinders. Review of the engine's installation and operations manuals revealed warnings indicating the following:
"The engine, by design, is subject to sudden stoppage."
"It is not a certificated aircraft engine. It has not received any safety or durability testing, and conforms to no aircraft standards."
"User assumes all risk of use, and acknowledges by his use that he knows this engine is subject to sudden stoppage."
TESTS AND RESEARCH
On June 12, 2004, the engine was examined. The one remaining propeller blade (the second was broken off at the hub) was manually rotated. Compression was noted, but with little resistance. The two cylinder heads were removed and it was noted that the aft cylinder head had less carbon build-up, indicative of a hotter operating temperature. The cylinders were then examined. The front cylinder walls did not show any sign of damage. The rear cylinder wall was examined and obvious damage was noted on the walls. Scrape marks in the same direction of piston movement was noted on the walls and metal shavings were noted at the top lip of the cylinder. The scraping was to the extent that it could easily be felt by touch.
Review of an ultralight news website (www.ultralightnews.ca) revealed the liquid-cooled Rotax engines were susceptible to "cold seizures." According to the website, it is necessary to bring the engine up to operating temperature prior to full power application. Failure to do so can result in "cold" seizure. This can happen when an engine has been left at idle for a long period of time just prior to takeoff or during a long slow approach from altitude with full power applied suddenly for a go around. The website also indicates that cold seizures are "probably the most reported problem that occurs on a 532/582 Rotax liquid-cooled engine." The problem occurs as a result of the engine coolant being cooled in the radiator, while the engine has been under load and creating heat, expanding the pistons. As the "cold" liquid enters the area around the cylinders, the cylinders shrink around the pistons resulting in the seizure. It is common for the engines to restart and run again after the engine cools down for a period of time on the ground.
According to a posting on the British Microlight Aircraft Association's (BMAA) website (www.bmaa.org), "the term 'cold seizure' is a bit of a misnomer. All seizures are caused by heat/friction. A cold seizure is where the piston expands faster than the bore it is traveling in and contacts the sides of the bore. These are also known as four corner seizures. "In the case of a mild seizure the engine may just lose power for a second or two, but will respond to throttle inputs and will recover when the throttle is advanced. This may happen a few times before a major seizure occurs. If the engine has experienced some previous mini seizures, the stoppage can occur anytime in flight as there is already some aluminum (off the piston) attached to the cylinder wall and galling (unwanted removal of aluminum from the piston to the cylinder wall) will be occurring at a variable rate." Photographs accompanying this information show scrapes on the piston and cylinders similar to those taken of the accident engine.