What happened
On a mission to combat a fire within the Lolo National Forest, an airtanker departed from its home airfield at 17:48 local time. The aircraft was configured for firefighting duties (Tanker 10) and was carrying 1,800 gallons of retardant along with two pilots.
The crew performed a high-altitude pass over the fire site, followed by a second approach toward a target located on a mountain ridge slope. Although the terrain appeared suitable for a retardant drop, no retardant was released during the maneuvers. Following the pass over the target area, the aircraft executed a sharp left turn and struck a heavily timbered hillside. The impact occurred while the plane was in a nose-low attitude of approximately 5 to 10 degrees and a left bank of roughly 40 degrees. The collision with the trees resulted in the total destruction of the aircraft and two fatalities.
Findings
Investigation into the accident revealed that the flight path during the left turn brought the aircraft dangerously close to the terrain. To maintain altitude and navigate the restricted turning space, the pilot attempted to increase the bank angle and load factor. This maneuver led to a significant rise in induced drag, which is particularly impactful at the low speeds characteristic of this flight phase.
The aircraft was already operating under critical conditions due to its low altitude and low airspeed. The increased demands placed on the engine by the higher load factors and bank angle caused the aircraft to enter the edge of a stall. As the crew applied aileron and elevator inputs to tighten the turn, the aerodynamic stall worsened. Because the power available was insufficient to overcome the drag and maintain flight, the aircraft entered a complete stall, making standard recovery procedures impossible due to the proximity of the ground.