NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The airplane collided with high-tension power lines in a mountainous area after deviating from the GPS approach procedure in instrument conditions. The airplane was equipped with a GPS navigation system incorporating a moving map feature. During the initial portions of the flight after departure, the TRACON sector controller working the flight initially believed the airplane was destined to another airport and issued a clearance accordingly, but corrected the clearance after the pilot questioned the controller. Shortly after this discussion, the pilot significantly deviated from his cleared course for unknown reasons in the general direction of the mistaken airport. The controller noticed the deviation and corrected the pilot's course. A second controller in the next sector the airplane would be worked by overheard the course correction, and inferred the pilot was somewhat confused. After handoff by the first controller, the second sector controller attempted to provide what he believed was a helpful method of handling the airplane in the transition to the GPS approach; however, these methods of clearing the pilot for the GPS approach were not in strict accordance with FAA Order 7110.65, and included an intercept angle with the final approach course that was greater than allowed. The airplane was on a modified downwind and proceeding to the initial approach fix (IAF) when the controller cleared the pilot to turn toward an intermediate fix between the IAF and the final approach fix (FAF) with the idea in mind that this course would be the same as a radar vector to the FAF. The pilot questioned the clearance, and then acknowledged it, and the airplane turned left toward the FAF, which was directly behind the airplane. The controller noticed that the left turn put the airplane heading toward high terrain and advised the pilot to turn right to go to the intermediate fix. After some additional confusion the airplane's track stabilized on the approach course after passing the intermediate fix. As the airplane passed the FAF the controller told the pilot to contact the tower, but gave him the frequency for the wrong airport. The pilot questioned the controller, who insisted the frequency was correct. The pilot then contacted the second airport tower and was told he was on the wrong frequency. Almost 1 minute elapsed between the pilot's acknowledgement of the erroneous frequency, and his initial contact to the correct tower. During this period the airplane's heading diverged approximately 90 degrees from the published final approach course toward rising terrain and the accident site. The Minimum Safe Altitude Warning alarms went off in the TRACON and in the tower, and the tower controller provided a low altitude safety alert based on the alarm by saying "check your altitude immediately;" however, at the time of the low altitude alert, the airplane was about 500 feet above the Minimum Descent Altitude (the accident site elevation was about 200 feet above the MDA.) and the alert was activated not because the airplane's altitude was below the segment minimums but due to the course and altitude being projected to come in contact with terrain in the near future. This may have confused the pilot and decreased the perceived urgency. The limitations of the radar display effectively masked the initial portions of the course deviation and the controller did not see the deviation for some 30 seconds; however, the controller did advise the pilot that he was off course as soon as he was aware of it. The pilot's unintelligible response was about the time the radar target return went into coast mode.