SO. LAKE TAHOE, CA, USA
N794PT
TUCKER THORP T18C
The airplane experienced a loss of engine power and the pilot initiated an emergency descent for a forced landing. A line service technician at a nearby airport reported hearing a pilot broadcast that he was at 8,500 feet (about 2,200 feet above the airport's elevation). The pilot indicated that he did not believe he could reach the airport. Witnesses observed the descending airplane. One witness saw the airplane between 400 and 500 feet above ground (water) level approaching the shore line and rolling into a left bank turn. The bank angle increased until the airplane was upside down. Thereafter the airplane descended in a near vertical nose low attitude until colliding into the lake, about 45 yards from shore. The crash site was about 5 miles from the airport. During the examination of the engine and propeller, no evidence was found of any pre-impact mechanical malfunctions. Because of impact damage, not all of the accessories could be tested. The odor of fuel and a petroleum slick was observed in the crash site area. The reason for the loss of engine power was not established.
HISTORY OF FLIGHT: On June 13, 1993, at 0845 Pacific daylight time, a Tucker Thorp T18C, N794PT, owned and operated by the pilot, crashed into Lake Tahoe, California. The experimental category airplane was destroyed. The pilot, who possessed an Airline Transport Pilot Certificate, and the pilot's son, who possessed a Commercial Pilot Certificate, were fatally injured. Visual meteorological conditions prevailed at the time of the personal flight. No flight plan was filed. The flight originated from Porterville, California, about 0730. A Lake Tahoe Airport line service technician reported that a few minutes before 0900 he had overheard a pilot's radio transmission over the UNICOM frequency. According to the technician, the pilot broadcast that he was at 8,500 feet over Lake Tahoe, was experiencing an engine problem, and did not believe he could reach the airport. The technician could not recall the airplane's registration number. One witness observed the aircraft's last few seconds of flight. According to the witness, when he saw the airplane it was flying in a southwesterly direction toward the shoreline, and it was an estimated 400 to 500 feet above the level of the lake. The witness stated that he observed the airplane in a steep left bank, and he estimated the bank angle at 90 degrees. The airplane's bank angle increased to 180 degrees, and the airplane (which was then upside down) rapidly descended in a nose low attitude until impacting the lake with the sound of a "thud." The airplane was found partially submerged in Lake Tahoe an estimated 45 yards off shore in four feet deep water. Several persons reported observing and/or smelling fuel upon their arrival at the crash site. For example, a Coast Guard employee estimated seeing two gallons of fuel in the water. A sheriff department official reported that a light skim of gasoline was on the water. A paramedic reported he smelled fuel within about 10 feet of the airplane. PERSONNEL INFORMATION: The pilot's flight record log book was examined, which listed his flights and check out in the accident airplane. The log book indicated that the pilot purchased the airplane on March 29, 1993. Between March and June, 1993, the log book listed the pilot as having flown the airplane on 22 occasions. AIRPLANE FUEL USAGE INFORMATION: The FAA Coordinator reported finding evidence that the airplane's fuel tank was completely full on June 12, 1993, when the pilot departed Carson City, Nevada, on a VFR flight plan to Porterville, California. The flight plan indicated that the airplane contained fuel for a four and one-half hour long flight. The anticipated flight time was listed at one and one-half hours. No evidence was found of the pilot having refueled after his arrival at Porterville. The accident occurred the following day during the pilot's return flight to Carson City. WRECKAGE, IMPACT AND EXAMINATION INFORMATION: The FAA Coordinator, who responded to the accident site area, verbally reported that most of the airframe, both propeller blade tips, and the engine were recovered. No evidence was found of fire. The FAA Coordinator further reported that no evidence was found indicating a catastrophic engine failure had occurred during the flight. The engine's ignition, fuel and lubrication systems were also examined. The right magneto was found separated from the engine. Sand was observed internally in both of the magnetos and neither produced a spark during rotation. The left magneto's impulse coupling was functional. All eight spark plugs were observed attached to the engine. Except for the top No. 3 plug, sand was observed impacted into all spark plug electrodes. The lead to the top No. 4 plug was not located. The fuel bowl mounted on the firewall assembly was disassembled and the screen was examined. Water and sand were present. The engine's fuel pump was found attached to the engine. The fuel pump was operated by hand. No fuel was present. The carburetor was found broken. A composite type float was present. The inlet fuel screen exhibited water corrosion. The oil sump assembly was found impact damaged and the oil quick drain was observed broken. The oil cooler lines to the cooler assembly were found attached to the engine. Lubrication was present under the valve covers and in the oil pump. Sand was observed in the oil pump and in the oil screens. Following the examination of the engine, the Lycoming Engine party representative and the FAA Coordinator reported that no evidence was found of pre-impact engine malfunctions. The propeller assembly was examined by Performance Propeller, Patagonia, Arizona. A representative from that firm opined that the propeller RPM was quite low (below 1,000 RPM) when the wood blades broke. The representative found no evidence of any pre- impact failure.
A TOTAL LOSS OF ENGINE POWER FOR UNDETERMINED REASONS, AND THE FAILURE OF THE PILOT TO MAINTAIN CONTROL OF THE AIRCRAFT WHILE MANEUVERING AT A LOW ALTITUDE.
Source: NTSB Aviation Accident Database
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