WPR15GA005 · Marsh Aviation S 2F3AT

The airline transport pilot was conducting a visual flight rules, public firefighting retardant drop flight on an active fire. The airplane, call sign "Tanker 81," was supported by two other aircraft: an orbiting Air Tactical aircraft (ATGS) that coordinated the aerial operations with ground units and an Aerial Supervision Module (ASM) that flew ahead of the tanker to define the route and the drop initiation point. After successfully conducting one drop, Tanker 81 was reloaded with fire retardant, and it then returned to the fire area. The accident pilot coordinated his next drop with the ATGS and then followed the ASM to the drop.

According to the ASM pilot, he flew the proposed drop route and initiated smoke to show the Tanker 81 pilot the desired drop location. The route included a slight left turn to final and a right turn on exit over descending terrain. The ASM had descended to 4,000 ft msl during the run, and described a predominate tree off to the right of the flightpath as a hazard, and instructed the accident pilot to stay to the left of it. The ASM pilot also described "very clear, smooth air over the drop area." He asked the Tanker 81 pilot if he had seen the smoke and if the route looked OK to him? The Tanker 81 pilot responded that "it looked OK." The ASM then climbed to 5,100 ft msl to lead the drop run. The ASM joined the pattern on the downwind and then told the Tanker 81 pilot that he could descend to 5,100 ft msl. He continued to describe the drop and flightpath to the tanker pilot and told him that there was some thin top smoke on final but that he could see through it and that they would break out of the smoke before reaching the drop area. He added that the last response he received from the tanker pilot was when he said, "OK."

Witnesses reported seeing the accident, and one of them provided a video that was taken from a vantage point along a mountain trail that was above Tanker 81's flightpath. The video revealed that while on approach, Tanker 81 struck trees with its left wing. Following the impact with the trees, the airplane entered a descending left roll, and it then impacted on the top of an approximate 800-ft-tall rock cliff. A fire erupted during the impact, the airplane fragmented, and the main wreckage was projected over the cliff and scattered over a wide river valley below the cliff face.

An examination of the wreckage site confirmed that the airplane's left wing had struck trees, and the outboard section of the left wing had separated from the airplane. Examination of the two engines revealed impact signatures consistent with their producing power at the time of impact. The pilot was in radio communications with either the fire base, the ATGS, or the ASM throughout the accident flight, and he did not report any concerns about the flight or mechanical issues.

Verbatim NTSB analysis and probable cause from the NTSB dataset