On July 16, 1994, at 1715 central daylight time, a Piper 28-140, N7079R, was substantially damaged when it came to rest in a corn field adjacent to Greater Kankakee Airport, Kankakee, Illinois. The instructional flight had just taken off from runway 27 at Greater Kankakee Airport, but it was unable to climb. The flight instructor and student pilot received minor injuries. The two passengers received no injuries. The 14 CFR Part 91 flight operated in visual meteorological conditions without flight plan. The instructor reported the airplane was loaded to gross weight with fuel and a total of four persons aboard. While attempting to takeoff from runway 27 (2644' x 300'), the instructor states, "the aircraft lifted off at approximately two thirds of the runway, but it would not climb out of ground effect." The airplane struck the tops of corn located at the end of the runway, impacted the ground, and came to rest in an inverted position. No preimpact mechanical abnormalities were reported by the instructor. A weight and balance calculation done by FAA Inspector Susan Gardner revealed the weight of the airplane exceeded the maximum gross weight limitation. The airplane was found to have been loaded outside of the center of gravity range listed in the airplane's flight manual. The FAA Inspector's statement and calculations are appended.