LAX94LA286

The flight was en route to portland over mountainous terrain. At 0940, the U.S. Forest service was notified of a fire and the aircraft wreckage was subsequently located in a saddle at the 6,480-foot level. The accident site is the only relatively clear area in the vicinity. At 1000, a helicopter reached the accident site and dropped water on the burning wreckage. The wreckage was found within a 23-foot-diameter area. An examination of the aircraft wreckage revealed damage consistent with a low-speed, moderate-angle controlled impact. The aircraft's engine had been modified to operate on 87 octane auto fuel. An inspection revealed the spark plugs were worn, with the electrodes found to have a gap in excess of .022 of an inch. None of the spark plugs were fouled. The fuel inlet screen exhibited a dark, wet substance. A thread compound was present and on the fuel inlet screen. The carburetor had composite floats installed. The two-piece venturi was found displaced in the carburetor throat. A lineman at lincoln had seen the aircraft being fueled from several cans the day prior to its departure from the lincoln airport.

History of flight

On July 16, 1994, at 0940 Pacific standard time, a Cessna 150D, N6052T, was destroyed by terrain impact and fire during a cross-country flight to Portland, Oregon. The aircraft was operated by the pilot. Visual meteorological conditions prevailed at the time and no flight plan was filed for the operation. The certificated private pilot and his passenger sustained fatal injuries. The flight originated from the Lincoln Municipal airport in Lincoln, California, about 0800 on the day of the accident.

A review of the radar data provided by the Federal Aviation Administration (FAA) air traffic division revealed that prior to the accident, the aircraft had been cruising between 7,600 and 8,400 feet before radar contact was lost.

An inspection of the wreckage by FAA inspectors and the Trinity County Sheriff Department revealed three, 2- to 3-gallon cans in the wreckage. One was found empty while the remaining two contained a small amount of a fuel-like substance.

The FAA inspector reported that a lineman had reported seeing the aircraft being fueled from several cans the day prior to its departure from Lincoln Municipal. He reportedly told the operator that the airfield regulations prohibited the type of refueling operation he was conducting. The operator reportedly acknowledged, but continued to refuel the aircraft.

Aircraft information

The aircraft was modified with the installation of a 150-hp Lycoming O-320 engine in accordance with Supplemental Type Certificate (STC) #SA-750CE. The engine had been further modified to operate on 87 octane automotive fuel in accordance with Supplemental Type Certificate #SA-633GL. The auto fuel STC specified the use of fuel having an anti-knock index specified in ASTM-D-439 including volatility classes A through E.

Communications

There were no reported distress calls from the aircraft prior to the accident.

Wreckage and impact information

The aircraft wreckage was located in the saddle of a mountain at the 6,480 foot level. The wreckage distribution was localized within a 23-foot-diameter area surrounding the initial point of impact. The impact site was surrounded by trees and rising terrain.

The propeller exhibited leading edge damage and chordwise scoring on one blade. That blade also was bent aft at a point near the root. The opposite blade exhibited only slight damage. The propeller spinner showed lateral crushing.

Valve train and gear continuity were established during a 360- degree crankshaft rotation. A thumb compression check established compression in all four cylinders.

The exhaust system was removed and examined. The muffler baffles were found to be intact.

The ignition system was examined. The spark plugs were visually inspected. All of the electrodes were worn and, dimensionally, were found to be in excess of .022 of an inch. All of the spark plug electrodes were dry with the exception of the top No. 1 plug which was wet with oil. Both magnetos (right Slick 4150, S/N 9040665R and left Slick 4251R, S/N 6029010) were destroyed by heat and could not be tested. The impulse coupler on the left magneto was found intact.

The fuel system was examined. The carburetor was removed and visually inspected. The fuel inlet screen exhibited a dark, wet substance. A thread compound was present on the threads and on the fuel inlet screen. The composite carburetor floats, which were installed, exhibited charring. No fuel was observed in the bowl. The two-piece venturi was found displaced. The air box was crushed with the valve assembly found in an intermediate position.

The lubrication system was examined. The oil suction screen was removed and visually inspected. Minor carbon deposits were present on the screen. The oil filter canister was cut open and the element visually inspected. The element exhibited heat damage and appeared free of contamination.

Medical and pathological information

An autopsy was performed by the Trinity County Sheriff-Coroner. Toxicological specimens were taken and tested by the FAA Civil Aeromedical Institute, with negative results for alcohol and all screened drug substances. Carboxyhemoglobin saturation was reported at 15 percent and cyanide was detected in the pilot's blood specimen.

Fire

The aircraft was involved in a postcrash fire. According to Trinity County Sheriff's deputies, the fire burned unchecked until U.S. Forest Service helicopters dropped water on the fire at approximately 1000.

Survival aspects

According to the Trinity County forensic pathologist, both occupants succumbed to thermal injuries resulting from the postcrash fire rather than impact trauma. He also noted that the pilot sustained left acute subdural hematoma prior to receiving thermal injuries.

Additional information

The aircraft was recovered and transported to an aircraft storage facility in Sacramento, California. The aircraft wreckage was subsequently released after examination to a representative of the registered owner.