Piper PA 28-140 N1729J accident near Mt Tom, Oregon

Probable cause

The noncertificated pilot's continued visual flight into instrument meteorological conditions, which resulted in spatial disorientation leading to the pilot's loss of control of the airplane and subsequent collision with mountainous terrain.

NTSB analysis

Radar data indicated that, after takeoff, the uncertificated, noninstrument-experienced pilot flew the airplane north toward the destination, which required the airplane to cross mountainous terrain, and climbed to an altitude of at least 6,300 ft mean sea level (msl). About 11 minutes after departure, the radar data showed an abrupt left turn to a southwest direction, which was followed by a loss of radar contact 19 seconds later. The abrupt left turn is indicative of a steep bank angle. The radar data also showed that the airplane descended rapidly over a ground distance of about 0.5 mile from at least 6,300 ft msl to 3,100 ft msl where it collided with terrain near the peak of a mountain. The steep left turn and the rapid descent are consistent with a loss of control. Further, the airplane's wreckage distribution was consistent with a high velocity collision with trees and terrain.

Weather observations indicated that instrument meteorological conditions (IMC) were likely present in the vicinity of the accident site around the time of the accident. The closest official weather observing station, located 11 miles from the accident site, reported a broken ceiling at 4,300 ft msl and an overcast cloud base at 5,000 ft msl. An unofficial weather observing station at an elevation of 2,100 ft, located 7 miles from the accident site, reported relative humidity greater than 90 percent, indicative of cloud or fog formation.

It is likely that the pilot encountered IMC conditions and lost visual reference to the ground or horizon. Given the pilot's lack of certification and instrument flight experience, the loss of visual reference likely resulted in spatial disorientation, leading to a loss of control of the airplane.

The pilot's toxicology testing detected amphetamine and donepezil in the muscle and liver; quetiapine in the liver; tetrahydrocannabinol (THC) in the liver, lung, and brain; and THC's inactive metabolite tetrahydrocannabinol carboxylic acid in the liver, lung, and brain. The pilot was likely being treated with donepezil for memory loss following a brain injury, but the condition being treated with quetiapine was not identified. While both a traumatic brain injury with memory loss and psychiatric disorder(s) could significantly degrade the pilot's cognitive skills and decision-making ability to safely operate the airplane, the investigation was unable to determine the extent of either condition, what role they played in the accident, or if the pilot had side effects from the medications. The toxicology results demonstrate that the pilot had used marijuana and amphetamine at some point before the accident, but the timing of use or blood levels around the time of the accident could not be obtained. Therefore, the investigation was unable to determine if the pilot's use of marijuana (source of THC) and amphetamine impaired his ability to safely operate the aircraft or if either drug contributed to the accident.

Text from the NTSB. Open the NTSB docket for WPR15FA152 for the full record.