Cessna P210N N6609P accident near Sheridan Lake, Colorado

Probable cause

The pilot's severe impairment from the combined effects of high levels of ingested alcohol as well as three impairing medications (zolpidem, lorazepam, and diphenhydramine), which resulted in his decision to attempt an aerobatic maneuver that the airplane was not approved for.

NTSB analysis

The private pilot was conducting a cross-country flight at 17,500 ft mean sea level (msl) while operating on a visual flight rules clearance. About 2 hours after takeoff, the pilot stated over the radio, "(unintelligible) I'm going down and I'm going down hard." Based on the pilot's speech, it became apparent to the controller that the pilot was experiencing some type of distress. The controller attempted to communicate with the pilot, concerned that he was possibly experiencing hypoxia, carbon monoxide exposure, or another medical condition that was affecting his speech and ability to control the airplane. Throughout the remainder of the flight, the controller provided numerous altimeter setting updates recommending that the pilot descent to a lower altitude in a continued effort to assist the pilot; however, the pilot did not acknowledge or reply to these requests. During three different radio transmissions, the pilot stated, "I can show you…" what the airplane can do. He also stated, "(unintelligible) guys want me to do Muller?", which is an aerobatic maneuver that involves a flat spin and recovery. (The airplane is not approved for aerobatics or spins.) Radar data indicated that the airplane entered a series of turns, climbs, and descents. The final recorded radar return indicated the airplane was about 9,200 ft msl. The airplane subsequently impacted a field in a flat spin. Examination of the airframe, engine, and airplane pressurization system revealed no mechanical malfunctions or anomalies that would have precluded normal operation.

Given that the airplane's descent did not improve the pilot's control of the airplane's heading or the quality of his communication with the controller, it is likely that the pilot's behavior was not the result of hypoxia.

Toxicology testing on the pilot was positive for ethanol at ranges between 0.247 gm/dl and 0.335 gm/dl, which is significantly higher than the legal limit of 0.040 gm/dl. While ethanol can be produced in tissues after death, this occurs by microbial action; and vitreous, where the levels were highest in specimens from the pilot, is typically a sterile fluid. In addition, an approximately half-full bottle of vodka was found in the wreckage, suggesting that the majority of the identified ethanol had been ingested. Further, the tested samples were positive for three additional impairing substances; diphenhydramine, lorazepam, and zolpidem. The pilot's impaired speech and behavior were most likely caused by the effects of high levels of alcohol along with effects from the three prescription medications, which likely led him to believe that he could perform maneuvers in the airplane that it was not capable of performing.

Text from the NTSB. Open the NTSB docket for CEN16FA188 for the full record.