SEA01LA133

During the after-takeoff climb in high density altitude conditions, the aircraft encountered a dust devil/whirlwind that altered its attitude and heading. Although the pilot was able to recover from this upset, the aircraft was then headed for the knoll of a small hill. The pilot therefore raised the nose of the aircraft in an attempt to clear the knoll, but in doing so he allowed the airspeed to deteriorate, and the aircraft subsequently stall/mushed into the terrain.

On July 10, 2001, approximately 1000 mountain daylight time, a Piper PA-28R, N8475C, impacted the terrain after taking off from Linberg Ranch, a private airstrip located about 17 miles north of Cut Bank, Montana. The private pilot and his passenger received minor injuries, but the aircraft, which is owned and operated by the pilot, sustained substantial damage. The intended destination of the 14 CFR Part 91 personal pleasure flight, which was being operated in visual meteorological conditions, was Glasgow, Montana. No flight plan had been filed. The ELT, which was activated by the impact, was turned off at the scene.

According to the pilot, because the takeoff took place on a rough grass airstrip, the aircraft accelerated slowly and lifted off near the departure end of the 2,600 foot runway. After becoming airborne, while flying just above stall speed, the aircraft flew through a dust devil/whirlwind. As it flew through the whirlwind, the aircraft rolled to the right and pitched nose-up. Although the pilot was able to recover from the whirlwind-induced upset, the aircraft was then heading for the knoll of a small hill. The pilot therefore raised the nose of the aircraft in an attempt to climb over the knoll, but the airspeed began to drop, and the aircraft subsequently stalled/mushed into the terrain.

At the time of the accident, the temperature was approximately 75 degrees Fahrenheit. The field elevation was 3,800 feet above mean sea level (MSL), and the altimeter setting at Cut Bank was 30.05 inches of Mercury. Based on these ambient conditions, the density altitude was calculated to be approximately 5,640 feet. It was also determined that the aircraft's weight was about 230 pounds below maximum allowable gross weight.

The pilot reported that there did not appear to be any malfunction of the engine or other aircraft system. A post-accident inspection of the engine did not disclose any evidence of a malfunction.