ERA13LA015

Before takeoff, a witness observed the pilot performing a preflight inspection, during which the pilot appeared to check the fuel system for contaminants. The airplane subsequently departed and was observed to climb to between 150 and 200 feet above ground level before a witness heard a loud “bang” and noted black smoke trailing from the airplane. Additionally, several witnesses reported that the engine was “running rough.” The airplane continued to fly about the same altitude with the engine sputtering and running rough, emitting puffs of black smoke every 1 to 2 seconds. Several witnesses indicated that before the airplane flew past the departure end of the runway, it stalled, entered a spin, and impacted terrain. Postaccident examination of the engine revealed crankshaft, camshaft and valve train continuity. Examination of the ignition system revealed no discrepancies. The carburetor was removed and bench tested, which revealed that it produced a richer-than-specified fuel/air mixture at several throttle positions, including full throttle, which would be used for takeoff. However, it is unlikely that the overly rich fuel/air mixture caused the symptoms reported by the witnesses. Although weather conditions at the time of the accident were conducive to serious carburetor icing at glide power, the airplane was not operating at glide power during the accident takeoff. The investigation was unable to determine the cause of the power loss.

On October 10, 2012, about 1815 eastern daylight time, an experimental amateur-built Velline’s Breezy RLU-1, N255JL, registered to Addison Aviation LLC, collided with trees following a loss of engine power during takeoff from Madison Municipal Airport (52A), Madison, Georgia. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 Code of Federal Regulations (CFR) Part 91 personal, local flight from 52A. The airplane sustained substantial damage and the private pilot, the sole occupant, sustained serious injuries. The flight was originating at the time of the accident. The pilot reported that he does recall planning to fly for the purpose of logging flight time; however, he has no independent memory of the accident flight. After getting out of the hospital he spoke with the persons who rescued him and during that conversation he recalled rolling the airplane out of the hangar, and having a young boy ask to sit in the airplane, but he told the boy that he was getting ready to fly. One witness reported observing the pilot perform a walk-around inspection which included checking the fuel system for contaminants. The pilot departed from runway 32, and one witness reported that the airplane became airborne about 750 to 850 feet down the runway. The airplane was observed to climb to between 150 and 200 feet, when a loud “bang” sound was heard and black colored smoke was noted trailing the airplane. Additionally, the engine was heard by several witnesses running rough. The airplane was observed to continue flying about the same altitude with the engine sputtering and running rough emitting puffs of black smoke every 1 to 2 seconds. The airplane flew past the departure end of the runway and by several witnesses accounts, the airplane stalled and entered a spin before impacting near a tree line. Inspection of the engine was performed following recovery of the airplane by a Federal Aviation Administration (FAA) airworthiness inspector. The inspector reported verifying crankshaft, camshaft, and valve train continuity. Good compression was noted at each cylinder, and the magnetos were properly timed to the engine. Spark was noted at all spark plugs during hand rotation of the engine, and inspection of the spark plugs revealed all contained, “…heavy black soot in color indicating engine running very rich.” The fuel tank and carburetor bowl contained 100 low lead fuel, and the fuel selector was in the on position. The airplane was then placed in the owner’s hangar, and subsequently the Marvel Schebler MA3 carburetor, serial number Y26-2904 was removed and retained for testing. Examination of the carburetor was performed with FAA oversight at the company that currently manufactures “Marvel Schebler” carburetors of that design, which they began since 2007 or 2008. The examination revealed the data plate was stamped with “VFM”, although they were not familiar with those markings. Historically, modification to a carburetorby installation of a 1-piece venturi requires stamping the data plate with a “V” and modification to a carburetor by installation of a metal float requires stamping the data plate with “MF.” The throttle plate and mixture levers moved freely as did the throttle shaft and plate. The throttle plate remained secured to the throttle shaft; both had a heavy accumulation of dirt. There were no obvious mechanical defects or missing parts. The venture was in place and “intact.” Red colored dirt was noted in the carburetor intake throat. The substance was not chemically analyzed. During separation of the body and bowl 3 of the 4 screws were noted to be lightly screwed down while the remaining screw was noted to be moderately tight. Following separation of the body and bowl, dirt was found inside the carburetor’s air passages. The float height setting was satisfactory and the float did not contain any fuel indicative of a hole in the float. The needle valve and seat were also in satisfactory condition, and the rubber tip of the needle valve exhibited normal seating wear. The positive retracting wire clip was in place on the needle and float, and the idle tube was in place which appeared to be serviceable. The body and bowl were reassembled in the as-found way for operational testing which revealed that the unit was .2 pounds-per-hour (PPH) less that specified but that is adjustable. At about 1/3 throttle, the carburetor was about 4 PPH richer than specified for the same throttle setting when compared with the standard carburetor, while at 2/3 throttle the carburetor flowed 5 PPH richer than specified. At full throttle, the carburetor flowed about 2.5 PPH richer than specified. With the exception of the slight richness, personnel of the carburetor manufacturer reported no other anomalies were noted during the bench testing. Review of the maintenance records revealed the carburetor (which is considered an on-condition item) was last overhauled on April 23, 1973. A surface analysis aviation weather report taken from Greene County Regional Airport (3J7) on the day of the accident at 1815, or the time of the accident, indicates in part that the temperature and dew point were 21 and 12 degrees Celsius respectively. The 3J7 Airport is located about 16 nautical miles and 098 degrees magnetic from the accident airport. Review of FAA Special Airworthiness Information Bulletin CE-09-35, with the subject Carburetor Icing Prevention revealed that based on the reported temperature and dew point at the nearby airport about the time of the accident, the conditions were favorable for serious icing at glide power.