On September 21, 2014, about 1205 eastern daylight time, a Grumman American AA-5A, N26676, operated by a private individual, was substantially damaged during a forced landing, following a partial loss of engine power during cruise flight near Homosassa, Florida. The private pilot was not injured and a pilot-rated-passenger incurred minor injuries. The personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the flight that departed South Lakeland Airport (X49), Lakeland, Florida, about 1130. No flight plan was filed for the planned flight to Harris County Airport (PIM), Pine Mountain, Georgia. The pilot reported that during cruise flight, about 1,500 feet above ground level, the engine began to intermittently run rough. The engine power loss became more consistent and the pilot was unable to maintain altitude. He attempted to divert to a nearby airport while the pilot-rated-passenger tried to restore engine power; however, the airport was 5 miles away and the airplane would not glide that far at its altitude. The pilot then attempted to perform a forced landing into a field. During the approach, the pilot-rated-passenger took control of the airplane. The airplane collided with powerlines and impacted the field, before coming to rest upright. The airplane was equipped with a Lycoming O-320, 160-horsepower engine. The airplane's most recent annual inspection was completed on January 1, 2014. At that time, the airplane had accrued about 1,580 total hours and the engine 29 hours since major overhaul. The airplane had flown about 2 additional hours from the time of the inspection, until the accident flight. Examination of the wreckage by a Federal Aviation Administration (FAA) inspector revealed damage to the wing spars. The inspector was able to rotate the propeller and verify camshaft, crankshaft and valve train continuity. He also attained thumb compression on all cylinders and the magnetos produced spark at all leads. He observed fuel in both fuel pumps and the carburetor. He did not observe any blockages in the carburetor venturi and noted that the airplane had about 25 gallons of fuel remaining at the accident site. When the inspector interviewed the pilot, the pilot reported that he momentarily applied carburetor heat when the engine began to run rough, but then turned it off after a few seconds because he did not observe any improvement in engine power. Review of an FAA Carburetor Icing chart for the temperature (70 degrees F) and dew point (68 degrees F) at the time of the accident revealed "Serious Icing (glide power);" however, the engine was at cruise power when the power loss occurred.