N4932B

HISTORY OF FLIGHT

On August 17, 1999, at 1131 hours Pacific daylight time, a Beech J35, N4932B, was destroyed when the aircraft impacted a tree and terrain short of the runway during an emergency landing approach at the Yuba County Airport, Marysville, California. The commercial pilot and a passenger, who held a private certificate, were seriously injured. Visual meteorological conditions prevailed for the personal flight, operated by the owner/pilot under the provisions of 14 CFR Part 91. The flight departed from the Marin (private) airport at San Rafael about 1045, and was destined for a private ranch airport near Caldwell, Idaho. No flight plan was filed.

When approximately 7 miles northeast of Marysville, the pilot radioed Sacramento Approach Control at 1116 that he was at 8,000 feet (msl) over Beale Air Force Base and was "having rough engine problems." He stated that he intended to land at Marysville. At 1119, the controller identified the aircraft on radar over Beale and the pilot reported Marysville in sight. The pilot said he intended to maintain his present altitude until over the field (Marysville) before making any further throttle position changes. At 1121, the pilot reported, "from the indications on the egp [EGT] it looks like I've lost half the engine." At 1124, the pilot reported he was over the airport descending at 500 feet per minute and still experiencing the rough engine. At 1128:14, the pilot radioed, "the cowling came off and I got oil coming through the windshield here." At 1128:54, the controller advised the pilot he was 2 miles north of the airport. At 1129:28, the pilot advised he was lowering the aircraft's landing gear. At 1130:15, the controller advised the pilot he observed him on radar on base leg 1.5 miles north of the airport and asked if the pilot still saw the airport. The pilot replied "three two bravo still has." The final communication with the aircraft was at 1130:31 regarding possible traffic, which the pilot acknowledged at 1130:43.

The passenger reported that when they were on left base leg for runway 14, the cowling flew open, oil filled the windshield, and the engine ceased delivering power.

The aircraft impacted a tree approximately 75 feet above ground level, and then came to rest in the West Linda Park about 0.75-mile northwest of the airport. At the scene, the No. 6 engine cylinder was separated from the crankcase, and engine components associated with that cylinder were found over a 40-foot radius around the aircraft.

According to paramedic personnel, the male occupant was seated in the left front seat and the female occupant was seated in the right front seat.

AIRCRAFT INFORMATION

According to the engine logbook for the aircraft, the engine received a top overhaul on January 29, 1999 at engine tachometer time 87.6 hours. At the accident site the tachometer read 129.4 hours. During the top overhaul, six factory new Teledyne Continental Motors cylinder assemblies were installed.

WRECKAGE AND IMPACT INFORMATION

The accident location was in an area of level grass covered terrain in the West Linda Park in the city of Marysville. From the accident location, the threshold of runway 14 at the Yuba County Airport is approximately 0.75 miles south. The latitude and longitude were 39 degrees 06.92 minutes north and 121 degrees 34.78 minutes west (GPS), respectively. The elevation was approximately 60 feet msl. There was no fire and all of the aircraft was present at the site except the No. 6 piston and some parts associated with the No. 6 cylinder installation on the engine.

There was a debris field oriented approximately north south, which was about 120 feet long. At the north end of the debris path were several tree branches, typically 2 inches in diameter lying on the ground. An adjacent tree showed evidence of fresh disturbance approximately 75 feet above its base. At the opposite (south) end of the debris path was the main aircraft wreckage, which was aligned with the nose pointing north.

About 35 feet north of the aircraft was an area of freshly disturbed dirt approximately 4 feet in diameter and 10 inches deep. Several pieces of window Plexiglas, typically 12 inches in size, most coated with a brownish liquid resembling oil, were located near the hole. Pieces of green glass were located about 15 feet east of the area of disturbed dirt. About 25 feet north of the aircraft was an engine connecting rod, minus the cap portion, and a piston wrist pin. About 30 feet west and southwest of the aircraft were two valve pushrods and pushrod housings.

The aircraft was upright and aligned with the nose pointing north. There was a crush plane oriented approximately 60 degrees from the longitudinal axis from the nose toward the right wingtip. The nose of the aircraft and engine were displaced about 60 degrees to the left and the engine was inverted about 135 degrees counter-clockwise. The right wing was destroyed outboard of the midspan and the main landing gear was extended. The inboard leading edge of the right wing exhibited crushing damage. The cabin area of the fuselage retained its shape although the Plexiglas windows were absent. The skin of the aft fuselage was separated on the left side aft of the cabin and exhibited compression damage on the right side opposite. The empennage stabilizer surfaces and two radio antennas on the top of the fuselage were coated with a brown liquid resembling engine oil. The brown liquid was streaked aft from the leading edge toward the trailing edge. The left wing exhibited two impact marks in the outboard leading edge, and the main landing gear was collapsed. One blade of the 3-bladed propeller was bent smoothly aft over its span about 60 degrees. The other two blades exhibited minor damage. None of the blades exhibited any chordwise striations, leading edge damage, or torsional bending. The flight controls were continuous. The four fuel tanks contained a clear blue liquid that looked and smelled like aviation fuel. The engine fuel selector was positioned on the right main fuel tank. The right main tank was ruptured and rescue personnel reported that fuel was observed draining from the tank onto the ground after the accident.

The No. 6 cylinder was located on the ground beneath the engine and remained connected to the exhaust manifold. The internal bore of the cylinder was visually undamaged, as were the intake and exhaust valves. The flange at the base of the cylinder was bent at the 6 o'clock position approximately 15 degrees. The cylinder skirt was broken at the 12 o'clock position. The exterior of the cylinder exhibited local damage to cooling fins. Two hydraulic valve lifters were also on the ground beneath the engine. Two valve pushrods and two pushrod housing tubes (four separate parts) were found approximately 25 feet southwest of the aircraft.

The engine crankcase where the No. 6 cylinder attached was broken away at the 12 o'clock position over an area about 4 inches diameter between the cylinder mounting base and the case backbone. The top two cylinder mounting studs were not located nor was the broken material from the crankcase. The upper forward, upper rear, and lower rear mounting studs were broken. The lower forward stud and the two lower center studs were present. None of the cylinder base nuts were present.

The No. 6 connecting rod and piston wrist pin were found 25 feet in front of the aircraft. The connecting rod exhibited scraping damage on one side along its length. One cap bolt was missing and the other was broken and was lodged in the hole of the rod. The piston wrist pin was undamaged except for a 0.2-inch dent in each end cap. The connecting rod bearings and rod cap were located inside the oil sump of the engine. One bearing half and the rod cap were damaged while the other bearing half was visibly undamaged. The No. 6 piston was not located.

The engine oil screen contained two small flecks of non-magnetic metal material. The engine fuel lines forward of the firewall contained a blue liquid resembling fuel. The spark plug electrodes were clean and undamaged but were wet with a fresh coating of a liquid resembling engine oil.

The engine was disassembled and further examined by the Safety Board investigator at the facilities of Teledyne Continental Engines in Mobile, Alabama, on October 26, 1999.

The engine had external damage to ignition wires, cooling baffle, and cooling fins. The core of the engine was intact except for the No. 6 cylinder assembly, which was separate. The intake manifold front cross tube was severed near the No. 6 cylinder and the intake "Y" tubes at the rear of the engine were separated from the engine. The fuel injection pump, control unit, and air valve were intact although the air valve inlet was blocked by deformed inlet box structure. The fuel distribution manifold (spider) had impact damage but was intact except for the attachment to the No. 6 nozzle. The injectors were free of debris. The air inlet path was clear of foreign debris. The exhaust manifold was intact on the right side up to the muffler connection and was broken from the cylinders at the base flanges on the left side. On cylinders No. 1 through 5, some cylinder base nuts had white torque seal applied, some case trough bolts had blue torque seal applied, and some top and all lower cylinder base nuts had no torque seal applied. The engine vacuum pump, starter, and alternator rotated freely by hand. The propeller governor turned by hand and pumped oil and the base screen was clear. The magnetos sparked and the spark plug electrodes were round and free of fouling.

The engine sump was removed and contained segments of material resembling piston rings and approximately 10 pieces of brittle, non-magnetic metal material typically 1/2 inch is size. The pieces were plated with a flat black finish. Also found were two bolts identified ...