On April 22, 1999, approximately 1208 Pacific daylight time, a Wells Baby Lakes, N92JW, registered to and operated by the pilot, was substantially damaged after it collided with the ground near a private airstrip in Monroe, Washington. The aircraft was being operated as a 14 CFR 91 personal flight. Visual meteorological conditions prevailed and no flight plan was filed for the local flight. The private pilot, the sole occupant, was fatally injured. There was no fire and no report of an ELT actuating. The flight originated from the Firstair Airfield, Monroe, Washington, approximately 45 minutes prior to the accident. A witness, located approximately one mile east of the accident site, reported seeing a red biplane flying "quite low over our farm." The witness stated it appeared the aircraft was practicing touch and go landings, "but never quite touching the ground." The aircraft continued to maneuver in the area for approximately 20 minutes. The witness reported that the aircraft was maneuvering approximately 40 feet above the ground when it abruptly nosed over and spiraled into the ground. The most current weight and balance data for the aircraft, dated May 02, 1992, showed a basic empty weight of 579.5 pounds. According to the aircraft's logbooks the recommended center of gravity is 14 inches aft of datum, plus or minus 1.5 inches, making the total range 12.5 inches to 15.5 inches aft of datum. The weight and balance data for the aircraft was computed with the aircraft having an electric starter, battery and a wooden propeller. Examination of the aircraft wreckage revealed that the aircraft had been modified from its original state. The aircraft's electric starter and battery had been removed and the original wooden propeller had been replaced with a McCauley metal propeller. The aircraft's logbooks did not reflect the above changes and no evidence of a revised weight and balance calculation for the aircraft was found. A calculated weight and balance, using the most current data, revealed that with a 210 pound pilot and twelve gallons of fuel(full fuel), the center of gravity is approximately 19.2 inches aft of datum. With the same pilot weight and six gallons of fuel, the aircraft's center of gravity is approximately 17.27 inches aft of datum.