The pilot requested, and was approved for a GPS approach. He was issued an altimeter setting, but did not acknowledge it. Radar data revealed that the airplane passed about 1 mile to the right of an intermediate approach fix, and was nearing the abeam position, about 1/2 mile to the right of the final approach fix. At both positions, the airplane was about 300 feet below the minimum segment altitude. After passing the final approach fix, the controller advised the pilot that radar contact was lost and the pilot acknowledged the transmission. No further transmissions were received from the pilot. The airplane impacted a tower, slightly left of the approach course centerline, at an elevation of about 1,350 feet. The minimum descent altitude along that approach segment was 1,800 feet. The setting found on the altimeter would have placed the airplane about 100 feet lower than it should have been. A witness stated that minutes after the accident, he looked up at the tower to check for damage, and saw that the top of it was "just in the bottom of the clouds." The airplane was certified for IFR operation; however, it was not equipped with an IFR-certified GPS receiver. A personal, hand-held computer with an antenna and integrated GPS receiver was found at the accident site. The software vendor had posted a warning on its website, which stated, "The system is not tested or approved by the FAA or any governmental agency and should not be used as a primary flight instrument."

The National Transportation Safety Board determines the probable cause(s) of this accident as follows: