Cessna 172S N665SP accident near North Bend, Washington

Probable cause

The pilot's physical impairment due to alcohol, which adversely affected his ability to operate the airplane and to maintain clearance from mountainous terrain while operating in dark night conditions.

NTSB analysis

During the local flight, which took place in dark night visual meteorological conditions, several witnesses reported observing the airplane’s lights at a low altitude and hearing the airplane’s engine running before the sound of impact. One witness, a certificated pilot, estimated that when he saw the airplane there was an overcast layer of clouds about 2,000 feet mean sea level (msl) with some lower level clouds and patchy areas of fog. Recorded radar data showed the flight departing the airport and ascending to an altitude of about 2,400 feet msl while traveling in a northeasterly direction. The data subsequently showed that the airplane descended on an east-southeasterly heading to an altitude of about 1,500 feet msl before radar contact was lost. The last recorded radar target was about 6 miles northwest of the accident site, which was located at an elevation of about 1,958 feet msl. The terrain along the pilot’s route of flight ranged between about 500 and 1,000 feet msl; the accident occurred as the airplane approached an area of rising (mountainous) terrain. A postaccident examination of the airframe and engine revealed no evidence of a mechanical malfunction or failure that would have precluded normal operation. Toxicology tests of the pilot revealed a blood alcohol concentration of 154 mg/dl. Federal Aviation Administration regulations prohibit operation of an airplane by persons with blood alcohol concentrations exceeding 40.0 mg/dL. It is likely that the pilot was impaired during the flight, which affected his ability to operate the airplane and maintain clearance from terrain.

Text from the NTSB. Open the NTSB docket for WPR12FA105 for the full record.