Accident Overview
On April 30, 2016, at approximately 1057 eastern daylight time, a Champion 7BCM, registration N7620B, experienced a partial loss of engine power and subsequently performed a forced landing to a grass field in Tyrone, Georgia. The airplane was substantially damaged. The airline transport pilot and one passenger were not injured. The aircraft was registered to a corporation and operated by the Dixie Wing of the Commemorative Air Force under 14 Code of Federal Regulations Part 91 as a revenue sightseeing flight. Day, visual meteorological conditions prevailed, and no flight plan was filed. The local flight had originated from Atlanta Regional Airport – Falcon Field (FFC), Peachtree City, Georgia, about 1040.
Pilot Report
According to the pilot, the airplane was level at 3,000 feet above mean sea level when the engine began to lose power. The pilot selected carburetor heat, but no improvement was observed; engine speed remained at 2,000 rpm. Carburetor heat was then turned off. The magnetos were checked and no significant change in performance was noted. Carburetor heat was re-applied with no improvement; the pilot left it on for the remainder of the flight. The airplane could not maintain altitude, so the pilot configured for a forced landing in a field. After touchdown, the airplane nosed down in high vegetation and the main landing gear collapsed. The pilot and passenger exited the airplane and were assisted by first responders.
Wreckage and Engine Examination
An FAA inspector examined the wreckage at the site. The airplane came to rest upright. Structural damage was evident to the engine firewall and forward fuselage. The main landing gear was collapsed under the airframe. The fuselage-mounted fuel tank contained an adequate amount of fuel. An initial cursory examination of the engine revealed no evidence of a mechanical failure.
The wreckage was recovered to the operator's facility for additional examination by two FAA inspectors and the NTSB investigator-in-charge. The engine was found intact and still attached to the airframe by the engine mount. External examination of the engine case and cylinders revealed no evidence of rupture or breach. All four top spark plugs were removed; the electrodes were normal in wear when compared to a Champion Check-A-Plug chart, but coated with a thin layer of black soot. The engine was turned manually using the propeller; suction and compression were observed on all cylinders and valve action was correct. The carburetor was removed and disassembled; the fuel bowl was clean and free of contaminants, with no water noted. The bowl contained a small amount of clean fuel that was light blue in color. All carburetor components were normal in appearance. The air intake to the carburetor was unobstructed. The magnetos were turned manually and produced a spark at all leads. The ignition harness was normal in appearance with no fraying or cuts noted.
Weather Conditions
According to the 1053 weather observation at FFC, located about 7 miles south of the accident site, the temperature and dew point were 79 degrees F and 63 degrees F, respectively. According to the carburetor icing probability chart in FAA Special Airworthiness Information Bulletin CE-09-35 (Carburetor Icing Prevention), dated June 30, 2009, the temperature/dew point at the time of the accident was in the area of serious icing at glide power.