What happened
While engaged in an aerial fire suppression mission for the California Department of Forestry, two Grumman TS-2A aircraft, identified as N442DF and N450DF, collided in mid-air. At the time of the incident, the aircraft were operating in a holding pattern near a wildfire, awaiting instructions for retardant drops. The Air Tactical Group Supervisor was orbiting at 1,000 feet above the tankers, who were maintaining a counterclockwise orbit at 3,000 feet mean sea level.
Investigation into the sequence of events revealed that N442DF was maneuvering within the established orbit, having swung wide to reposition itself behind another aircraft. The pilot of N442DF had configured the aircraft for a drop, with flaps extended. Meanwhile, N450DF was flying a direct path toward the center of the fire, a trajectory that had not been observed from other tankers that day. The collision occurred at approximately 2,500 feet altitude, below the standard orbit level. During the impact, the engine, cockpit, and right propeller of N442DF struck and severed the empennage of N450DF.
Findings
Several contributing factors were identified in the collision. The aircraft were operating in an environment where the Air Tactical Group Supervisor's logs did not show a check-in for N450DF, and other pilots on the radio frequency did not recall the aircraft announcing its arrival. A significant factor was that a ridgeline had recently been cleared by N450DF, which likely obstructed the view of both pilots, preventing them from seeing the oncoming aircraft.
Furthermore, the investigation highlighted a lack of standardized operating procedures. The California Department of Forestry lacked a formal operating manual or established entry points for the holding orbits. While training materials suggested that incoming tankers should establish radio contact and enter the orbit at a specific altitude to maintain visibility, the absence of codified, mandatory procedures contributed to the unsafe flight conditions.