19981129032539A

Experimental mini 500 was the subject of an alnot since 11/29/98. Acft wreakage was located on 12/2/98. (.19) on November 29, 1998, about 1515 eastern standard time, a homebuilt mini 500, N500GH, was destroyed during a collision with trees near Midland, Virginia. The certificated private pilot/owner/builder was fatally injured. Visual meteorological conditions prevailed for the local flight that originated from the manassas airport (hef), manassas, Virginia. No flight plan was filed for the personal flight conducted under 14 CFR part 91. A family member reported the pilot missing after not returning from his normal 40 to 45 minute flight. The pilot's vehicle remained parked outside his hangar the next morning, and the federal aviation administration issued an alert notice. The civil air patrol's search discovered that tower personnel at hef recorded the helicopter taking off at 1400. Witnesses stated that they saw the helicopter near leesburg airport, leesburg, Virginia, about 1430, and near nokesville, Virginia, about 1500, on November 29th. The helicopter was located on December 2, 1998, about 1530, in a wooded area approximately 1/4 mile north/northeast of the warrenton-fauquierairport, warrenton, Virginia. A survey of the debris field discovered that the initial impact point was the top of a 50-foot tall tree. Tree limbs, measuring 4 to 6 inches in diameter, were cut horizontally and found near the base of the tree. One of the helicopter's rotors was lying on the ground near the tree; the other was snagged on a fracture tree limb about 30 feet above the ground. The main wreckage was lying on its left side between two trees 5 feet apart, and about 35 feet south of the initial impact point. All major components of the helicopter were found at the accident scene. Examination of the flight controls revealed continuity at the time of impact. The engine logbook indicated that in August 1998, at 200.4 hours on the hobbs meter, the owner replaced both pistons, rings, wrist pins, rod bearings, thermostat, and head o-rings. The hobbs meter in the wreckage read 218.7 hours. Inspection of the engine revealed two different types of spark plugs were utilized, one of each type in the two cylinders. The spark plugs were wired such that one magneto fired one type of spark plug. Rotation of the crank shaft revealed 4 point scuffing on the cylinder and the power take-off (pto) piston. (-23) no narrative shown (.4) the pilot/owner was flying his amateur-built helicopter and crashed in a wooded area. Examination of the helicopter revealed that the non-certificated 2-cycle engine had experienced a power loss due to a 'cold seizure.' About 18 hobbs meter hours prior to the accident the pilot had replaced pistons, rings, wrist pins, rod bearings, thermostat and head o-rings. Metallurgical examination of the pto cylinder walls revealed deposits from the side (piston skirt) of the accident pto piston and a previous pto piston, indicative of a prior cold seizure event. Although the kit helicopter was built according to plans, the engine manufacturer did not recommend several of the engine modifications found on the accident helicopter. Additionally, the engine manufacturer did not recommend the installation of this model engine in the helicopter and published the following warning with the engine manual: 'this engine, by its design is subject to sudden stoppage. Engine stoppage can result in crash landings, forced landings or no power landings. Su ch crash landings can lead to serious bodily injury or death.'