On May 20, 2009, about 2050 central daylight time, a Cessna 150L airplane, N17214, was substantially damaged during a forced landing following a loss of engine power near Baton Rouge, Louisiana. Visual meteorological conditions prevailed at the time of the accident. The certified flight instructor (CFI) and student pilot received minor injuries. The flight was being conducted under the provisions of Title 14 Code of Federal Regulations Part 91 with a visual flight rules (VFR) flight plan. The cross country training flight originated from Baton Rouge Metropolitan Airport (BTR), Baton Rouge, Louisiana, en-route to False River Regional Airport (HZR), New Roads, Louisiana. The pilots were conducting a night, cross country training flight. They stated to investigators they were about seven miles from HZR when the engine experienced an unexplained drop in revolutions per minute (RPM) from 2,450 to 2,200 RPM. The student pilot suggested to the CFI to turn on the carburetor heat, but the CFI elected not to turn the carburetor heat on and to turn around and return to BTR, about 16 miles away. En route to BTR the engine performance continued to decay until the airplane could not continue in level flight. The airplane landed in a field approximately four miles from BTR. During landing the airplane nosed over and came to rest inverted. Examination of the airplane showed impact damage to the vertical tail and both horizontal stabilizers, the empennage was cracked, and the engine was separated from the airplane. No evidence of an engine mechanical failure was found and the fuel was found to be free of contaminants. Meteorological readings for BTR at 2053 indicated the temperature was 26 degrees Celsius and the dew point was 16 degrees Celsius. The carburetor icing chart found in FAA - P - 8740-24, Tips on Winter Flying, shows the airplane operating in an area of potential "Light Icing – glide or cruise power." The carburetor icing chart from DOT/FAA/CT-82/44 Publication indicated the airplane was operating in an area of "icing – glide and cruise power," and "serious icing at glide power."