On July 20, 1998, at 0715 central daylight time, a Nord Stampe SV4C acrobatic airplane, N123SV, was destroyed following a loss of control while maneuvering near Orvilla, Texas. The instrument rated private pilot, sole occupant of the airplane, was fatally injured. The airplane was owned and operated by a private individual under Title 14 CFR Part 91. Visual meteorological conditions prevailed throughout the area for the local acrobatic flight for which a flight plan was not filed. The flight departed from the Eagle's Nest Estates Airport (2TSG), near Midlothian, Texas, approximately 20 minutes prior to the accident. According to the operator, the airplane departed for a scheduled early morning precision aerobatics flight in preparation for an upcoming overseas aerobatics competition. A witness who resides approximately two miles north of the accident site, reported observing the airplane practicing acrobatics maneuvers within the approved acrobatics box. The witness further stated that she observed the airplane "attempting to recover to the upright position from a nose dive." During the recovery maneuver, the airplane entered an "arching left turn which continued to ground impact." The witness further reporting hearing the sound of the engine revving up during the attempted recovery sequence. She added that the airplane disappeared out of her sight descending out of control. The wreckage of the 1946 vintage Belgian designed, French built biplane was found by law enforcement officers in an open pasture approximately a mile southwest of the O'Brien Airpark (F25), near Orvilla, Texas. Physical evidence and signatures at the accident site indicate that the airplane impacted the ground in a nearly vertical attitude in a slight right turn, on a measured heading of 135 degrees. All of the aircraft components were located within a 40 foot radius of the point of impact. Continuity was established to all the flight controls. There was no evidence of pre-impact or post impact fire. The pilot was wearing an emergency parachute. She was operating the airplane from the aft seat. Examination of the 5-point restraining system for the aft seat by the investigator in charge did not reveal any signs of deformation or stretching of the webbing. Fire/rescue personnel that responded to the accident site confirmed that the pilot was found unrestrained in the area of the aft seat.