Incident Description
An aircraft collided with terrain after descending to 600 ft above ground level and encountering a weather phenomenon. The phenomenon prompted an airspeed decay and uncommanded loss of altitude. The accident aircraft was part of a flight of three; the other two aircraft experienced the same phenomenon to a lesser degree, apparently because of their higher altitude above ground level.
Pilot Observations
The pilot of one of the accompanying aircraft landed on a nearby road after seeing the accident. While proceeding to the scene, the pilot observed a "huge dust devil." The pilot also reported that the wind would shift from 300 degrees to about 120 degrees, then shift to 60 degrees with a buffet before returning to the prevailing 300 degrees.
Weather Conditions
The two closest weather stations, located 45 or more miles away, are separated from the accident area by mountain ranges.
Accident Aircraft Pilot Actions
The pilot of the accident aircraft was stabilized in flight with 10 degrees of flaps at 85 knots when a drop in airspeed was noted—first to 70 knots, then to 60 knots—along with a vertical speed of 500 to 700 feet per minute descent. When the airspeed continued to drop, the pilot added full power and retracted the flaps. The aircraft continued to descend at 1000 to 1200 feet per minute until impact.