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 private pilot was practicing flight maneuvers required to obtain a commercial pilot certificate during daytime visual flight rules weather conditions. A witness saw the airplane flying in slow counterclockwise circles while descending with the engine power at idle. He reported strong gusting winds at the time. Radar data showed the airplane completing four counterclockwise orbits and then beginning a descending clockwise orbit. The last two data points indicate a rapid, vertical descent greater than 6,000 ft per minute. Wreckage and impact signatures revealed that the airplane impacted the ground in a nose-low, near-vertical attitude with little to no forward movement, consistent with an aerodynamic stall/spin. Examination of the airframe and engine found no abnormalities that would have precluded normal operation.
Weather conditions in the accident area included strong gusty winds, low-level wind shear, clear air turbulence near the terrain, and possible mountain wave activity at mountain top level. The weather information that the pilot obtained before departure indicated wind at 6 knots and no gusts. No records were located to indicate that the pilot had obtained an official weather briefing before departure, thus he may not have been aware of the gusting winds and the potential for low-level wind shear and turbulence which could have contributed to his failure to maintain aircraft control. The radar data, the witness's description, and the damage to the airplane are consistent with the pilot exceeding the airplane's critical angle of attack while maneuvering, resulting in the airplane entering an aerodynamic stall with a subsequent spin and descent to ground impact.