On January 2, 1997, at 0845 central standard time, a Beech C90A, N1552D, was substantially damaged upon impact with a tower during approach near Rio Grande City, Texas. The airplane, owned by the Sheerin Charter Service L.C., of San Antonio, Texas, and operated by Raytheon Aircraft Services, also of San Antonio, was being operated under Title 14 CFR Part 91, at the time of the accident. The airline transport rated pilot, sole occupant of the airplane, was not injured. Visual meteorological conditions prevailed for the business flight for which an instrument flight plan was filed. The flight originated from the San Antonio International Airport at 0740. According to the pilot, the IFR portion of his flight plan was terminated after he found a clearing in the broken ceiling near the Diamond "O" Ranch airstrip, near La Gloria, Texas. The pilot planned to navigate south along the road for approximately 25 nautical miles to the Starr County Airport, near Rio Grande City. The pilot added that while en route to the airport, at an estimated altitude of 1,000 feet MSL, the left engine propeller impacted guide wires and the outer portion of the right wing impacted the tower. According to the Brownsville sectional chart, the tower which is located on the west side of the road, is 1,002 feet MSL high (519 feet AGL). In the narrative portion of the enclosed NTSB Form 6120.1/2, the pilot stated that he "checked [the] map to track his position along highway 755, and when he looked up, the tower was right in front, too late to take evasive action." The pilot reported that after the collision with the tower, he aborted the approach and proceeded to the McCallen Miller International Airport, near McCallen, Texas, where after extending the landing gear manually, an uneventful landing was made. Examination of the airframe revealed that a 65-inch section of outboard portion of the right wing was damaged, two propeller blades on the left engine propeller were damaged, and a 12-inch incision was found on the left mid wing section.