LAX02FA166 · SOCATA TB-21

During a sales demonstration flight, the pilot descended into the upsloping face of mountainous terrain about 17 nm north of the destination airport. The accident occurred under dark, nighttime, visual meteorological conditions, and after about a 22-minute flight. Illumination of the moon's visible disk was 19 percent. No roads or ground structures were in the vicinity to provide ground reference or to illuminate the accident area terrain. The direct course between the departure and destination airports (71 nm apart) was 180 degrees magnetic. Recorded radar data indicated that during the last 3 minutes of flight, the airplane's average ground track was 176 degrees, and its average ground speed was 168 knots. The radar ground track ended near the centerline of the direct course between the departure and destination airports, and about 1/4-mile north of the initial point of impact (IPI). The wreckage distribution path was 640 feet long on a magnetic bearing of 177 degrees. An examination of the impact ground scars disclosed that the airplane was in controlled flight in a shallow descent when it collided with the terrain. Review of the radar derived accident airplane's flight track in conjunction with the associated underlying terrain and the ambient lighting conditions revealed that the terrain would have been, at best, marginally visible to the pilot. Initially during the descent, the lights of the greater Phoenix area would have been visible to the pilot in the distance, but the area would have disappeared from the pilot's view seconds before impact. The airplane was equipped with an autopilot, a KLN 94 global positioning satellite receiver, and a KMD 550 multifunction color display that, if operated in the topographic mode, had the capability to display terrain elevation information. During the wreckage examination of the airframe's structure and the engine, no evidence of any preimpact failures or malfunctions was found. The avionics components were found too impact-damaged to provide data. Accordingly, the investigation was unable to ascertain if the pilot was using the multifunction display to receive topographic data while descending toward the destination airport. The KLN 94 and the KMD 550 Pilot's Guides state: "CAUTION NEVER USE THE TOPOGRAPHIC ELEVATION DISPLAYED ON THIS EQUIPMENT AS YOUR SOLE REFERENCE FOR TERRAIN AVOIDANCE."

Verbatim NTSB analysis and probable cause from the NTSB dataset