WPR12FA369

A partial loss of engine power for reasons that could not be determined because examinations revealed no evidence of mechanical anomalies with the airframe or engine that would have precluded normal operation and the pilots’ decision to continue the departure in dark night conditions with the engine not producing full power.

While taxiing to the ramp, the airplane's engine shut down, and it took the pilots numerous attempts to restart it. After parking, the pilots reported to the attendants that the airplane's fuel/air mixture was difficult to establish at such a high-density altitude and that, if the engine was operated too lean, its temperature exceeded normal operation parameters. Later that day, the pilots departed in dark night conditions. During the takeoff roll, most of the runway length was used before the airplane began to climb. Several witnesses reported that the airplane appeared to be having engine problems and, after being airborne for about 3 seconds, it descended into terrain. Additionally, some witnesses reported that the engine sounded as if it was not producing full power and that the ascent seemed labored. The airplane impacted trees located on flat terrain about 2,400 feet from the end of the runway. The main wreckage was consumed by postimpact fire. Examination of the accident site revealed that the right wing impacted a tree in a wings-level attitude. The postaccident examinations revealed no evidence of mechanical anomalies with the airframe or engine that would have precluded normal operation. Although it could not be confirmed, it is likely that the left-seat pilot was the flying pilot and that the right-seat pilot, who owned the airplane and had been consuming alcohol before the flight, was not the pilot-in-command.

The Airport/ Facility Directory (AFD), indicated that the Lake Tahoe Airport (TVL) runway 36 was about 8,540 feet long and 100 feet wide. The runway surface was composed of asphalt. The airport elevation was 6.269 feet msl. The uncontrolled airport was situated in class "E" airspace. In the remarks section of the AFD was a note "345 ft. trees, 5700 ft. from runway, 500 ft. right of centerline, 15:1 slope to clear." The airport was situated in the valley on the south shore of the lake, with the departure end of the runway about 2.5 nautical miles south of the shoreline. The mountain peaks and ridges that surrounded the valley rose to elevations in excess of 9,900 feet msl. The Department of Coroner Sacramento completed autopsies on both pilots. The FAA Toxicology and Accident Research Laboratory performed toxicological testing on their specimens. The results of analysis of the right-pilot's specimens revealed the following: >> 33 (mg/dL, mg/hg) Ethanol detected in Blood (heart) >> 54 (mg/dL, mg/hg) Ethanol detected in Vitreous >> 41 (mg/dL, mg/hg) Ethanol detected in Brain >> 40 (mg/dL, mg/hg) Ethanol detected in Urine >> 37 (mg/dL, mg/hg) Ethanol detected in Muscle The results of analysis of the left-pilot's specimens were negative for carbon monoxide, cyanide, and ethanol. Following the on-site investigation an additional examination of the wreckage was conducted on August 28, 2012, at the facilities of Plain Parts, Sacramento, California. Present to the examination was a Safety Board investigator, as well as representatives from both Piper Aircraft and Textron Lycoming. Airframe The left wing and its respective control surfaces were mostly consumed by post impact fire. The left main landing gear, wingtip, and several pieces of skin were located at the main wreckage and remained with remnants of the main spar. The aileron control cable was secure to the bellcrank and continuous to the control wheel chain. The balance cable was secure to the bellcrank attach point and continuous to the right side aileron bellcrank. The left fuel filler cap was found in the skin pieces and observed to be secured in place. The inboard portion of the right wing was consumed in the post impact fire. The right main landing gear structure remained with a portion of the main spar. Both the aileron control cable and the balance cable were secure to the bellcrank. The control cable was continuous and secure to the control wheel chain. The balance cable was continuous and secure to the left bellcrank. The right fuel filler cap was found in the skin pieces and observed to be secured in place. The flap torque tube was loose in the wreckage, with the surrounding structure having been consumed by fire. The flap handle was positioned between the fully retracted position and first notch (10-degree) setting. A majority of the empennage was consumed in the post impact fire. The remaining parts of the empennage were manufactured from steel and included the lower rudder bellcrank hinge point (with stop bolts), one stabilator hinge (with stop bolts) and the control cables. Both rudder cables were secure to the rudder bellcrank and continuous to the rudder pedals in the cockpit. Both the stabilator cables were secure to the balance tube and continuous to the control wheel T-bar in the cockpit. The stabilator pitch trim drum showed a nine-thread upper extension, which according to the Piper representative was consistent with a position of about a 3-degree nose-up trim. Removal of the fuel selector revealed that it was positioned on the left main fuel tank. The remainder of the fuel system had been consumed by fire. The instruments and radios were destroyed by impact and fire and provided no useful information. Engine An external visual examination of the engine revealed that it remained attached to the engine mounts. The engine case and accessories sustained deformation from a combination of impact energy forces and being subjected to the post impact ground fire. There was no evidence of pre impact catastrophic mechanical malfunction or fire. The top spark plugs were removed; no mechanical damage was noted and the electrodes and posts exhibited a light ash gray coloration, which corresponds to normal operation according to the Champion Aviation Check-A-Plug AV-27 Chart.; the upper No.2 plug had a light film of oil, which is consistent with the engine coming to rest inverted. The ignition harnesses were consumed by fire, but appeared to have been attached from both magnetos and their respective spark plugs. The single drive dual magneto was found securely clamped at the mounting pad and had been subjected to fire. The magneto sustained varying degrees of damage that rendered the unit inoperative and therefore, could not be functionally tested. The crankshaft was rotated by hand utilizing the propeller. The crankshaft was free and easy to rotate in both directions. "Thumb" compression was observed in proper order on all six cylinders. The complete valve train was observed to operate in proper order, and appeared to be free of any pre-mishap mechanical malfunction. Normal "lift action" was observed at each rocker assembly. Clean, uncontaminated oil was observed at all six rockerbox areas. Mechanical continuity was established throughout the rotating group, valve train and accessory section during hand rotation of the crankshaft. The cylinder assemblies were removed, examined and photographed. The cylinder(s) combustion chamber and barrels remained mechanically undamaged, and there was no evidence of foreign object ingestion or detonation. The valves were intact and undamaged. There was no evidence of valve to piston face contact observed. The pistons were intact. The ring assemblies at each piston were intact and free to rotate within their respective ring land. According to the Lycoming representative, the gas path and combustion signatures observed at the spark plugs, combustion chambers and exhaust system components displayed coloration consistent with normal operation. There was no oil residue observed in the exhaust system gas path. The exhaust system was found free of obstructions. The vacuum pump, mounted on the accessory case, remained affixed to its respective flange. The drive coupler was melted due to thermal effect. The rotor/vanes were undamaged when opened for examination. The oil suction screen was found secure and uncontaminated by any pre-mishap debris. The oil filter was destroyed by fire. There was no evidence observed of any pre-mishap lubrication system contamination found during the examination. The turbocharger system components remained secure at their respective mountings and had sustained varying degrees of thermal effect damage resulting from the post impact ground fire. The turbocharger compressor and turbine impellers remained intact and undamaged. The turbine was free to hand rotate. The turbocharger was disassembled and remained free of pre-impact anomalies. Each exhaust system clamp was secure at each location. The exhaust bypass butterfly valve remained intact and undamaged. All engine compartment fuel lines were found to be in place and secure at their respective fitting of each fuel system component. Each fuel system component sustained some degree of thermal effect damage that rendered them unsuitable for testing. The fuel injection servo remained securely attached at the mounting pad of the plenum. The fuel servo had sustained moderate thermal effect damage resulting from the post impact fire. The throttle and mixture control cables were found securely attached at their respective control arms on the servo. The servo fuel inlet screen was found properly installed and free of contamination. The fuel injection servo and induction system were examined and observed to be free of obstruction. The fuel injection nozzles remained secure at each cylinder wi