Cessna 172M N4395R accident near Ogden, Utah

Probable cause

The pilot's failure to maintain clearance from the water while flying over a lake with glassy surface conditions. Contributing to the accident was the pilot's use of three impairing medications.

NTSB analysis

The commercial pilot and private pilot-rated passenger departed on a local flight in day visual meteorological conditions and climbed to a peak altitude about 2,370 ft above ground level. The airplane then entered a gradual, wings-level descent during which it began to fly over a large lake. The airplane impacted the water and subsequently sank.

The airplane was mostly intact and exhibited no evidence of mechanical failures or anomalies that would have precluded normal operation. Given the condition of the airplane, flight track, altitude data, and the proximity to land, it is likely that the pilot intentionally descended the airplane to low altitude over the lake. It is also likely that the lake exhibited a glassy surface due to low wind conditions about the time of the accident, which would have reduced depth perception and made it difficult for the pilot to judge the airplane's height above the water. Additionally, toxicology of the pilot revealed the presence of three different impairing medications. It is likely that he was experiencing combined adverse effects of these three central nervous system depressants, which contributed to his failure to maintain clearance from the water while performing low-altitude flight.

Text from the NTSB. Open the NTSB docket for WPR18FA063 for the full record.