Navion NAVION A N4898K accident near Adrian, Oregon

Probable cause

The pilot’s failure to maintain aircraft control while in cruise flight due to spatial disorientation, which resulted in an exceedence of the design stress limits of the aircraft and led to an in-flight structural failure.

NTSB analysis

The non-instrument rated pilot departed on the 530-mile cross-country flight and headed west toward mountainous terrain. Recorded data plots from the pilot's Global Positioning System (GPS) receiver disclosed that after following a river in the valley, he began to fly over mountainous terrain that comprised the western landscape. Shortly thereafter, the pilot made a 180-degree course reversal, which was presumably done in an effort to circumnavigate inclement weather conditions. After continuing northeast for about 13 miles, the pilot began to head west again over the mountains. The flight continued for 26 miles and the airplane made a steep right turn, creating a "hook" type flight path. The last radar plots show a sudden increase in elevation, which is likely where the airplane began to breakup in flight. The wreckage was located about 2,000 feet in front of the last radar hit and about 3,700 feet below the last recorded altitude; it was inside the hook-shaped flight path. A weather facility located about 13 miles from the accident site, reported overcast cloud conditions at 2,900 feet above ground level (agl) about 20 minutes prior to the accident. Satellite imagery depicted an extensive area of nimbostratus clouds over the accident site and the observations surrounding indicated light rain and mist were present. The wreckage debris was scattered over an estimated 1,000-foot area of hilly terrain. At the beginning of the debris field were large sections of the right wing, with the far north area containing the engine, in indication that the right wing likely departed the airplane first. A post accident examination revealed that the wings and tail section showed evidence of a positive overload deformation pattern, with indications of upward bending of the wings and downward bending of the horizontal stabilizer. There was no evidence of mechanical malfunction or failure with the engine or airframe.

Text from the NTSB. Open the NTSB docket for WPR09FA391 for the full record.