NTSB Identification: LAX07LA130.
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Accident occurred Sunday, April 15, 2007 in Sedona, AZ
Probable Cause Approval Date: 11/29/2007
Aircraft: Beech 35-B33, registration: N9556Y
Injuries: 3 Fatal.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The single engine airplane impacted the slope of a bluff 200 feet short of, and below, the runway and was destroyed during the ensuing post impact fire. The airport is located on a plateau, with terrain that drops off steeply at both ends of the single runway. 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 that are 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." A pilot, who had landed at the airport just before the accident airplane, reported severe turbulence and a 30-knot windshear 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 wings angle of attack, and therefore, decreased the stall margin. As it dropped below the level of the runway, a witness reported that the airplane 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. 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 that is recommended at this airport, which 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. Medications that were identified in the pilot's toxicological report had been prescribed to treat his 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.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's inadequate compensation for the high wind conditions and wind shear encounter on final approach, that led to a failure to maintain an adequate airspeed and a stall.
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