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On April 11, 2000, at 1207 hours Pacific daylight time, a Beech B36TC single engine airplane, N6791P, impacted utility lines and a residence after experiencing a loss of control while returning to land following takeoff at the Fullerton, California, airport. The aircraft was destroyed during the impact sequence and post crash fire. The commercial pilot, who was the sole occupant, received fatal injuries. The aircraft was being operated as a personal flight by the pilot/owner under 14 CFR Part 91 when the accident occurred. The flight originated from the Fullerton Municipal Airport at 1203, and was destined for Van Nuys, California. Visual meteorological conditions prevailed at the time of the accident and no flight plan was filed.
The Air Traffic Control Tower (ATCT) local controller at Fullerton Municipal Airport reported that on takeoff, the pilot radioed that the aircraft door had opened and he was requesting permission to return for landing. The pilot was cleared for a left downwind approach to runway 24 and was told he would be number two to land behind a Cherokee that was on the downwind leg. The controller then asked the pilot if he had an emergency, to which the pilot replied, "no emergency." The pilot acknowledged his clearance and reported he was looking for the traffic. He subsequently reported he had the Cherokee in sight.
The controller reported he then heard the same voice say "Emergency, I got . . ." There were no further transmissions reported from the pilot.
Witnesses on the ground reported the aircraft was seen trailing dark smoke immediately after takeoff. Witnesses at locations along the downwind portion of the approach reported seeing grayish or light smoke. A witness near the accident site reported he heard the engine sounds stop prior to the crash. Another witness, who was a 9,500-hour Beech A36 pilot, reported he observed the airplane in a steep climb with a trail of black smoke from the exhaust, as if "the mixture was richer than necessary." He added that the aircraft stopped climbing and he lost sight of it behind trees; however, he observed the airplane again on the downwind leg approximately 600-800 feet above ground level. The witness stated the nose of the aircraft was high and the airplane was slow. As the airplane started its turn to base, it entered a 1.5-turn spin and crashed. This witness reported the landing gear were down and the flaps were up.
The commercial pilot held single engine, multiengine, and instrument airplane ratings. He was issued a second-class medical certificate on March 10, 1999, with no limitations. According to Federal Aviation Administration (FAA) records, the pilot reported having accumulated 2,182 total flight hours on his last medical certificate application. The pilot was the registered owner of the aircraft since December 1985.
The airplane was manufactured and issued an airworthiness certificate in January 1984, and utilized a Continental TSIO-520-UB six-cylinder, turbocharged engine and a 3-bladed McCauley propeller. The aircraft maintenance records were not located; however, the insurance adjuster provided endorsements and inspection checklists from the aircraft's last annual inspection, which took place on September 3, 1999. At the time of the last annual, the airplane and engine had accumulated a total of 1,028.7 hours.
The airplane was equipped with an auxiliary fuel pump, which is controlled by a switch located adjacent to the landing gear selector handle. The auxiliary fuel pump switch has three positions; OFF, LO, and HI. The LO position is used for priming the engine during hot starts and to supply a low boost to the fuel flow during all flight conditions. The HI position is used for priming the engine during cold starts and also to provide an alternate source of fuel pressure in the event the engine-driven fuel pump fails. According to the pilot operating handbook (POH), the "HI boost must not be used during the flight unless the engine-driven fuel pump has failed. The increased pressure of the HI boost will overdrive the fuel control unit producing abnormally high fuel flows, which, in turn, will cause engine roughness. In some cases, engine combustion my cease." The auxiliary fuel pump is not equipped with a position guard.
The POH also describes an "UNLATCHED DOOR IN FLIGHT" situation by indicating that "If the cabin door is not properly latched, it may open in flight. This may occur during or just after takeoff. The door will trail open approximately 3 inches but the flight characteristics of the airplane will not be affected, except the rate of climb will be reduced. Return to the field in a normal manner. If practical, during the landing flare-out have a passenger hold the door to prevent it swinging open."
WRECKAGE AND IMPACT INFORMATION
The airplane impacted power lines and a home in a residential area less than 1 mile southeast of the airport. The airplane came to rest within the home and erupted in flames upon impact, extensively damaging both the house and airplane. Review of photographs taken at the accident scene revealed that the majority of aircraft wreckage came to rest in the living room of the house.
Examination of the wreckage revealed that the flaps were found in the retracted position and the landing gear was found extended. The cabin door latch was examined and no damage or distortion was noted.
The engine sustained impact and fire damage, and was found separated from the airframe, and the propeller assembly was found separated from the engine. The propeller hub was shattered and the three propeller blades sustained varying degrees of fire and impact damage. Two of the three propeller blades displayed chordwise scratching, one of which sustained leading edge gouges. The third blade was bent aft and had approximately 8 inches of its tip missing, and displayed a leading edge gouge near its fracture surface. The number 2 rocker arm cover was partially melted from the cylinder exposing the rocker arms. The vacuum pump, starter, oil filter adapter, both magnetos, and propeller governor were found separated from the engine accessory section. The alternator was separated from its mounting pad. The fuel control housing was found melted away. The fuel pump was burned and its hoses were charred. The fuel pump was removed and its drive coupler was intact. An examination of the spark plugs by a NTSB investigator revealed that the plugs appeared sooted and black. According to the Champion Spark Plug Check-A-Plug chart, this spark plug condition and coloration is consistent with a rich air/fuel mixture.
The engine was sent to the manufacturer's facility in Mobile, Alabama, where it was examined at a later date. The engine turbocharger was sent to the manufacturer's facility in Torrance, California, where it too underwent examination at a later date.
TESTS AND RESEARCH
On April 13, 2000, the turbocharger was disassembled and inspected at the manufacturer's facility under the observation of an FAA inspector. The turbocharger assembly sustained extensive fire damage and the compressor housing was broken. The impeller blades were found bent in the opposite direction of rotation near their tips and score marks were noted on the inside of the housing. No anomalies were noted that would have prevented its operation.
On September 14, 2000, the engine was examined by a Safety Board investigator, an aircraft manufacturer air safety investigator, and engine manufacturer representatives. Disassembly of the engine revealed that there was no metallic debris in the oil sump noted and the pickup tube screen was clear. The engine oil pump was disassembled and the gears were coated with oil and did not display any significant signatures. All of the cylinder head components were found intact. The cylinders were removed and their barrels and pistons were covered with dark black soot. No additional anomalies were noted with the cylinder and piston components, the crankshaft, and the camshaft. The magnetos were placed on a magneto test stand for a functional test. The right magneto produced a spark at each ignition lead. The left magneto did not produce a spark. Closer examination of the left magneto revealed that the points displayed an oxidized contact surface. The oxide was removed with an abrasive cloth and the magneto produced a spark in each ignition lead.
The engine manufacturer reported that if the auxiliary fuel pump is turned to the "high" position while the engine is at full throttle, there will be no appreciable loss of power. This will cause; however, dark smoke to become visible from the exhaust because this creates a rich air/fuel mixture. As the throttle is reduced, the power loss will become excessive and the visible smoke appears lighter. As the throttle is reduced below 24 inches of manifold pressure, the engine will cease combustion.
On June 7, 2000, an exemplar Beech aircraft was operated through three phases of flight at the manufacturer's facility (Raytheon Aircraft Company). The test was conducted to learn the results of engine operation with the auxiliary fuel pump in the HI position. The first of the three phases was a static ground run conducted at full throttle. The exemplar engine stabilized with a manifold pressure of 36 inHg, an engine rpm of 2,620, and a fuel flow of 32.3 gallons per hour (GPH). The auxiliary fuel pump was then placed in the HI position and the engine began running rough and subsequently lost power. Black smoke was observed coming from the exhaust stack. When the engine rpm dropped to 800-1000 rpm, the auxiliary fuel pump was turned off and the engine combustion resumed. This phase test was conducted twice with the same results.
The second phase was accomplished as the airplane was on takeoff roll. Full power was set at 36 inHg, the engine rpm at 2,650, and a fuel flow of 33 GPH. As the airplane rolled past the 100-foot mark, the auxiliary fuel pump was selected to the HI position. The test pilot stated he sensed a loss of engine power; however, the engine continued to run smoothly. Black smoke was observed exiting the exhaust stack as the airplane climbed with the auxiliary fuel pump on HI.
The third phase of the test consisted of two overflights with the auxiliary fuel pump in the HI position. Black smoke was observed exiting the exhaust stack. The pilot stated he had the manifold pressure set at 36 inHg, the engine rpm at 2,700, and the fuel flow was at 42 GPH with the auxiliary fuel pump in the HI position. He added that the engine experienced a slight loss of power, but the engine operation remained smooth. The throttle was then reduced slowly for landing and the engine began to run rough at 35 inHg. The engine manifold pressure started to fluctuate at 34 inHg. Once the pilot brought the engine manifold pressure back to 31 inHg, the engine experienced a total loss of power. The test was repeated with the same results. The test pilot reported he attempted to keep the engine running by moving the throttle through various settings; however, the engine would not continue to run unless the auxiliary fuel pump was turned off.
A toxicological test was conducted on the pilot for carbon monoxide, cyanide, ethanol, and drugs. The test results were negative.