History of Flight
On July 5, 2009, at approximately 1301 Pacific daylight time, a Cessna 150J, N51172, operated by a private individual, experienced a loss of control during the initial climb from Lake Tahoe Airport in South Lake Tahoe, California. Seconds after lifting off from runway 18, the airplane entered an uncontrolled descent and struck terrain adjacent to the airport. Visual meteorological conditions prevailed, and no flight plan was filed. The flight was conducted under 14 CFR Part 91 and was originating at the time of the accident.
A witness preparing for departure on runway 18 reported that the accident airplane accelerated on the runway centerline, became airborne, and climbed to an estimated 100 feet above the runway with an unusually high nose-up pitch attitude. No smoke was observed trailing from the airplane. The airplane turned left and appeared to enter a left spin as it rapidly descended from view. The witness also heard the pilot broadcast a "mayday" call seconds prior to impact. Two other witnesses on the airport provided consistent accounts, with one noting a 90-degree left turn before the nose-down turning descent, while the other thought the turn was more extensive.
Pilot Information
The 41-year-old pilot held a private pilot certificate with ratings for airplane single-engine land and instrument airplane, last issued on April 25, 2001, when the instrument rating was added. The original private pilot certificate was issued on June 25, 1999. His most recent medical certificate, a second-class medical, was issued on July 26, 2005, with the limitation that corrective lenses be worn. No recent personal flight records were found. On the July 2005 medical application, the pilot reported 430 total flight hours, with 50 hours in the previous six months. On the May 2002 application, he reported 425 total hours and 25 hours in the previous six months.
Aircraft Information
The pilot purchased the airplane approximately two months before the accident. Maintenance records indicate the airplane was maintained on an annual inspection basis. On May 25, 2007, at a total time of 6,092.45 hours, an annual inspection was performed, which included installation of a carburetor overhauled by Central Cylinder Service, Inc. The carburetor was a Model MA-3SPA, serial number BE 74-9525. The next annual inspection was due by May 31, 2008, but was performed on November 17, 2008, at an engine tachometer time of 3,362 hours and total airplane time of 6,509.67 hours. No further carburetor maintenance was recorded. By the accident date, the carburetor had been in use for about 491 hours since overhaul. The airplane's Continental O-200-A engine had been overhauled and reinstalled, with an approximate total time of 4,809 hours at the accident. The airplane total time was about 6,583.6 hours. The airplane had flown about 73.9 hours since the last annual inspection. Last engine maintenance (oil change) was on May 20, 2009, and last airframe maintenance (lights and fuel strainer O-rings) was on May 22, 2009.
Meteorological Information
At 1253, the South Lake Tahoe Airport METAR reported clear skies, visibility 10 miles, temperature 79°F (26°C), dew point 27°F (-3°C), wind from 200° at 11 knots gusting to 20 knots, and altimeter 30.19 inHg. The density altitude was calculated to be 8,708 feet.
Airport Information
Lake Tahoe Airport is located in a mountain valley at an elevation of 6,264 feet. Mountains and ridges surrounding the valley exceed 9,900 feet MSL. The airport has a single asphalt runway, 18/36, 8,544 feet long and 150 feet wide. The Airport Facility Directory notes runway 18 is preferred for arrivals and runway 36 for departures.
Wreckage and Impact Information
The accident site was in a level mountain meadow on U.S. Forest Service land east of and adjacent to the runway. Ground cover consisted of grass and scrub brush up to 5 feet high. A ground scar was found about 50 feet in front of the airplane with fragments of the left fiberglass wing tip. The engine was crushed backward into the firewall with rotational crush deformation on the spinner. The forward fuselage was at a 45-degree angle to the ground. Both wings exhibited leading-edge crush deformation with accordion folds at about 45 degrees to the longitudinal axis. The empennage was buckled at the rear baggage bulkhead and displaced downward and to the right. Control continuity was established except for the rudder cables, which were trapped in crush damage. The fuel selector was in the "ON" position. Approximately 12 gallons of blue liquid with an odor of 100LL aviation gasoline was drained; the gascolator bowl contained fuel with sediment and about one ounce of water. The carburetor was intact, with about 2-3 ounces of fuel in the bowl, no contaminants, a clear finger screen, metal floats, and a functional accelerator pump. The propeller, a McCauley 1A101, remained attached; one blade had S-bending and leading edge damage, the other was bent forward about 10 degrees with similar damage.
Medical and Pathological Information
The pilot sustained fatal injuries; an autopsy by the El Dorado County Sheriff-Coroner listed the cause of death as blunt force traumatic injury. Toxicology tests were negative for alcohol and all screened drug substances.
Tests and Research
Between July 23 and 24, 2009, the accident engine was examined at TCM's Mobile, Alabama facility. The engine was started and run up to about 2,000 rpm with the throttle at three-quarters open. A pronounced vibration and roughness increased with rpm. When the throttle was advanced beyond three-quarters, engine rpm decreased. The test was terminated. The accident carburetor was replaced with an exemplar carburetor, after which the engine operated normally up to full power at 2,650 rpm, meeting all specifications. The accident carburetor was disassembled and found to be missing the pin that secures the metal floats to their pivot point. Marks indicating rubbing interference were present on the edge of a float and the side of the bowl. Spark plugs showed normal combustion signatures after the exemplar carburetor was installed, although the #4 upper plug initially appeared carbon fouled but cleared with normal operation.
Probable Cause
The official probable cause is not stated in the source.