On January 31, 1997, about 1300 hours mountain standard time, a Bellanca 17-30A, N6638V, was substantially damaged during a forced landing near Scottsdale, Arizona. The pilot and his passenger received minor injuries. Visual meteorological conditions prevailed for the personal cross-country flight and no flight plan was filed. The flight originated at North Las Vegas, Nevada, at 1015. The pilot contacted the Scottsdale Air Traffic Control Tower and was advised to enter a right base leg for runway 21. The pilot stated that when he was about 4 miles from the airport at 2,500 feet msl, the engine suddenly dropped to idle, it did not quit, and the throttle had no effect on the rpm. He stated that he immediately noticed approximately 1/4 tank of fuel and tried switching tanks, but could not get a restart or increase from idle. According to FAA inspectors, the fuel selector was found on the left outboard fuel tank. Both outboard fuel tanks were found to be empty.