At 1720 eastern time, a Cessna 172N struck a tower while flying the GPS Rwy 21 approach to Mount Sterling-Montgomery County Airport, killing the pilot and passenger. During the approach, which involved a shortcut requested by the pilot and approved by the controller, the pilot was advised to maintain 3,000 feet until established on the approach. The controller told the pilot to switch to the Unicom frequency twice, but the pilot said he wanted to stay with the controller in case of a missed approach. The airplane tracked parallel to but about a mile west of the approach course and the altitude fluctuated between 2,300 feet and 2,500 feet for much of that segment of the approach. The controller lost radar contact and informed the pilot, which the pilot acknowledged. Weather conditions reported at the time included broken ceilings at 500 feet and 2,100 feet, overcast at 2,500 feet. Visibility was four miles in fog. The airplane hit the tower about 75 feet below its peak and 415 above the ground. The elevation of the accident site was about 1850 feet msl. The airplane was not equipped with an IFR-certified GPS receiver and the pilot apparently had been relying on a handheld computer with an antenna that contained an integrated GPS receiver to fly the approach. The pilot had 478 hours of flight experience and 52 hours of actual instrument experience.