Undetermined · NTSB CEN15LA026
STEPHENSON STOL CH 701 — Mount Vernon, IN
| Date | October 24, 2014 |
| Location | Mount Vernon, IN |
| Aircraft | STEPHENSON STOL CH 701 (amateur-built) |
| Purpose of flight | Personal |
| Conditions | Dusk · Visual Meteorological Cond |
| Phase / occurrence | Prior to flight Miscellaneous/other |
| Pilot age | 69 |
| Pilot total time | 987 hrs · Building experience |
| Time in type | Unknown |
| Fatalities | 1 |
Probable cause
NTSB findings
- Personnel issues-Physical-Impairment/incapacitation-Alcohol-Pilot - C
- Personnel issues-Physical-Impairment/incapacitation-Prescription medication-Pilot - C
- Personnel issues-Action/decision-Info processing/decision-Decision making/judgment-Pilot - C
- Environmental issues-Physical environment-Object/animal/substance-Wire-Awareness of condition - C
- Personnel issues-Psychological-Attention/monitoring-Monitoring environment-Pilot - C
- Aircraft-Aircraft oper/perf/capability-Performance/control parameters-Altitude-Not attained/maintained - C
What happened
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.