Amateur-built STOL CH 701 N34WS accident near Mount Vernon, Indiana

Probable cause

The pilot’s impairment due to the ingestion of alcohol and sedating medications, which led to her improper decision to conduct low-level flight, affected her ability to safety operate the airplane, and resulted in her failure to maintain clearance from power lines.

NTSB analysis

The private pilot was conducting a local personal flight. A witness who was working in a field reported observing the pilot flying the airplane about 30 ft above ground level and 50 ft to his right. The airplane banked right and then impacted power lines. The power lines arced when the airplane contacted them, and the airplane subsequently caught on fire and was fully engulfed in fire when the witness arrived at the accident site. An examination of the airplane did not reveal any preimpact anomalies that would have precluded normal operation.

Toxicological testing detected ethanol at 0.148 grams per deciliter (gm/dl) in the vitreous (Federal Aviation Administration regulations only allow 0.040 gm/dl of ethanol) and relatively similar levels of ethanol in the pilot's brain and blood specimens, which indicates that most of the ethanol was likely due to ingestion rather than postmortem production; therefore, she was likely intoxicated and impaired by ethanol at the time of the accident.

In addition, the pilot had significant levels of diazepam and diphenhydramine in her heart blood. The detected levels for both drugs were likely therapeutic; however, in regular use, diazepam causes sedation and diphenhydramine causes marked sedation. Therefore, the pilot was likely impaired by both diazepam and diphenhydramine at the time of the accident.

In summary, the pilot's judgment and psychomotor functions were likely significantly impaired by a combination of ethanol intoxication and the effects of both diazepam and diphenhydramine at the time of the accident. The combined effects of these impairing substances likely led to the pilot's improper decision to conduct low-level flight, affected her ability to safely operate the airplane, and resulted in her failure to maintain clearance from power lines.

Text from the NTSB. Open the NTSB docket for CEN15LA026 for the full record.