Accident Overview
A single-engine airplane impacted the slope of a bluff 200 feet short of, and below, the runway. The aircraft was destroyed during the ensuing post-impact fire. The airport is situated on a plateau, with terrain that drops off steeply at both ends of the single runway.
Weather and Wind Conditions
Wind gusts at the runway surface were recorded at 38 knots. According to FAA publication AC 00-57, "Hazardous Mountain Winds and Their Visual Indicators," strong winds at the crest of a ridge or level with a mountain peak can create moderate or greater turbulence, strong up and down drafts, and very strong rotor and shear zones. Wind shear is defined as a sudden, drastic shift in wind speed, direction, or both that may occur in the horizontal or vertical plane.
Pilot Reports and Witness Observations
A pilot who had landed at the airport just before the accident reported severe turbulence and a 30-knot wind shear at the approach end of the runway, and transmitted that information to the accident pilot. According to witnesses, the accident airplane appeared to get low and slow while on final, likely encountered an abrupt wind shear zone, and descended below the elevation of the approach end of the runway. To maintain the airplane flying and to avoid the terrain, the pilot would have had to raise the nose, which increased the wing's angle of attack and decreased the stall margin.
As the airplane dropped below the level of the runway, a witness reported that it assumed a nose-high attitude, and the engine sounded as if it were operating at high rpm and "straining against the wind." The wing tips wobbled up and down, indicative of a stall, before the airplane rolled to the right and impacted rising terrain short of the runway.
Approach Characteristics
According to another pilot who routinely flew with the accident pilot, the accident pilot routinely flew approaches that were shallower than the 3.5-degree glide slope approach path recommended at this airport. The airport is equipped with a precision approach path indicator (PAPI) lighting system set to 3.5 degrees. In this instance, the pilot let the airplane drop well below the recommended glide slope during the approach to this runway.
Toxicology
Medications identified in the pilot's toxicological report had been prescribed to treat ongoing medical conditions and relieve pain. While the medications can cause impairment or spatial disorientation, the clear weather on this day, the low levels of medication found in the pilot's system (suggesting no recent use), and the circumstances of the accident make it unlikely that the medications had an effect on the pilot's ability to control the aircraft.