On June 23, 2002, at 1127 eastern daylight time, a homebuilt Pulsar, N5123B, was substantially damaged during a forced landing, following a loss of engine power in Bentleyville, Pennsylvania. The certificated private pilot was not injured. Visual meteorological conditions prevailed and no flight plan was filed for the flight that departed Greene County Airport (WAY), Waynesburg, Pennsylvania, destined for Rostraver Airport (P53), Monogahela, Pennsylvania. The personal flight was conducted under 14 CFR Part 91.

The pilot reported that when the airplane was about 10 miles from Waynesburg, en route to Monongahela, the airplane's engine lost power. He attempted to restart the engine unsuccessfully, and then performed a forced landing to a hayfield.

The pilot reported that he did not hear any unusual sounds or notice any change in engine instrument readings, before the loss of engine power. He said, "the engine just wound down and died." The pilot stated that he refueled the airplane on the morning of the accident, and departed from Waynesburg with 16 gallons of fuel, or approximately 3 hours of flight time.

A Federal Aviation Administration (FAA) inspector performed an on-scene examination of the airplane. According to the inspector, damage to the airplane was sustained by both wings and the landing gear. In addition, one propeller blade was separated from its hub. A flight continuity check was performed, and no mechanical anomalies were noted. Visual examination of the fuel tank revealed a significant amount of fuel, and no leaks were observed in the fuel lines. Observation of the engine revealed metal chips on top of the number 2 cylinder.

The 2-stroke Rotax engine was removed from the airplane and further examined under the supervision of an FAA inspector. An attempt to rotate the engine revealed a "grinding and loose" sound. Inspection of the chamber beneath the MAG cylinder revealed a large amount of metallic debris (Rotax identifies the cylinder closest to the magneto as the MAG cylinder and the cylinder closest to the power output shaft as the PTO cylinder). In addition, one of the rod bearings adjacent to the MAG connecting rod was missing.

Further disassembly of the engine revealed extreme markings of impingement of small particulate matter on the MAG cylinder piston dome and combustion chamber. Upon removal of both cylinders, small particulate matter resembling the MAG connecting rod bearing and missing thrust bearing was identified within the case. Disassembly of the crankcase revealed fretting of the cylinder head sealing rings as well as excessive side play between the connecting rod and crankshaft cheeks (in the area of the missing thrust bearing). Debris damage was also observed to the crankcase, the rotary valve and drive shaft gear.

Examination of the airplane and engine logbooks revealed that the engine was rebuilt in September 2001, and had accumulated 59 hours of time since then.

An excerpt from the engine manufacturer's operating manual revealed:

"Danger! This engine, by its design, is subject to sudden stoppage! Engine stoppage can result in crash landings. Such crash landings can lead to serious bodily injury or death.

Never fly the aircraft equipped with this engine at locations, airspeeds, altitudes, or other circumstances from which a successful no-power landing cannot be made, after sudden engine stoppage.

Warning! Although these engine types have undergone considerable durability testing, this engine is not a certified aircraft engine. It has not received any individual safety or durability testing and conforms to no aircraft standards. It is for use in experimental and ultralight uncertified aircraft and vehicles only, in which an engine failure will not compromise safety.

User assumes all risk of use and acknowledges by his use that the knows this engine is subject to sudden stoppage."

The weather reported at Allegheny County Airport (AGC), West Mifflin, Pennsylvania, 19 miles to the north, included variable winds at 4 knots, 6 miles visibility with haze, and clear skies.

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