WPR11FA188 · Aviat Aircraft Inc. A-1C-180

Two airplanes of the same make and model were repositioning together to the same destination and were flying about 1 mile apart from one another. The pilot of the lead airplane reported that shortly after departure, they encountered some light rain, but saw no evidence of ice. As both airplanes approached a mountain pass near the accident site, they encountered light snow with a cloud ceiling of about 1,200 feet above ground level and 3 to 4 miles visibility. The lead pilot heard a blind transmission from the pilot of the accident airplane saying he was "on the edge of a stall." No further radio transmissions were received from the accident pilot. The lead pilot stated that at the time of the radio transmission, he had no evidence of icing on his airplane or anything abnormal about the flight characteristics of his airplane. Witnesses located near the accident site reported observing the two airplanes and that the second airplane, which was about 1/2 to 1 mile behind the first airplane, appeared to be "wobbling" back and forth before it suddenly nosed downward into terrain. Review of weather conditions near the time of the accident revealed no potential for icing below about 11,000 feet.

Review of the recovered data from the accident airplane's GPS revealed that the airplane began a descent in the last 3 minutes 57 seconds of recorded data. The data showed an increase in groundspeed for the immediate 44 seconds following the start of the descent from 78 knots to 85 knots; however, the groundspeed then decreased to about 53 knots over the following 2 minutes 56 seconds. The last recorded data point was located about 0.3 mile south of the accident site and about 50 feet above ground level.

Wreckage and impact signatures were consistent with a stall and subsequent spin with a right-wing, nose-low impact. Postaccident examination of the airframe, flight control system, and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.

Toxicology tests on the pilot were positive for quinine, commonly found in tonic water and occasionally used to treat leg cramps, and sertraline, an antidepressant, which is commonly marketed as Zoloft, and its metabolite, desmethylsertraline. Review of the pilot's medical records revealed that the pilot did not report the usage of these medications on his most recent medical certification application. The degree of the pilot’s cognitive impairment from these medications could not be determined.

Verbatim NTSB analysis and probable cause from the NTSB dataset