IAD01FA070 · Piper PA-32R-301

The instrument rated pilot obtained weather briefings for his destination, which reported instrument meteorological conditions, including fog, mist, low visibilities and ceilings. The pilot then departed and flew to his destination, where he was cleared for an ILS approach. The airplane flew along the localizer course, and about a 1/2-mile from the approach end of the runway, the airplane initiated a climb and made a left turn toward the east. The airplane continued to turn left and flew north. It then began a series of left and right hand ascending and descending turns to various altitudes. During the last 3 minutes of flight, the airplane made 18 ascents and descents, with vertical speeds varying between positive 4,600 and negative 6,000 fpm, and it's altitude varied between 600 and 1,800 feet msl. Two witnesses heard the airplane fly loudly overhead before it collided with terrain, and reported that the weather was very foggy. At the time of the accident, weather reported at the airport included zero visibility, fog, vertical visibility 100 feet. According to FAA Flight Training Handbook Advisory Circular (AC) 61-21A, "If neither horizon or surface references exist, the airplane's attitude must be determined by artificial means - an attitude indicator or other flight instruments. Sight, supported by other senses such as the inner ear and muscle sense, is used to maintain spatial orientation. However, during periods of low visibility, the supporting senses sometimes conflict with what is seen. When this happens, a pilot is particularly vulnerable to spatial disorientation." Two independent toxicology reports detected chlorpheniramine, a sedating antihistamine, in the pilot's blood and urine.

Verbatim NTSB analysis and probable cause from the NTSB dataset