El Portal, CA, USA
N449DF
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.
HISTORY OF FLIGHT On October 7, 2014, about 1623 Pacific daylight time, a Marsh Aviation S-2F3AT airplane, N449DF, call sign "Tanker 81," impacted terrain while maneuvering in Yosemite National Park near El Portal, California. The airline transport pilot sustained fatal injuries, and the airplane was destroyed. The airplane was registered to the United States Department of Agriculture and operated by CAL FIRE. On this fire, it was under the operational control of US National Park Service (NPS), as a public firefighting flight. Visual meteorological conditions existed near the accident site about the time of the accident. The airplane had departed Columbia Airport (O22), Columbia, California, at 1608. According to a CAL FIRE representative, Tanker 81 was stationed at the Hollister, California, air base and had been dispatched to the Dog Rock fire in Yosemite National Park. The airplane successfully made one fire retardant drop and then proceeded to O22 to reload. 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. Upon returning to the fire area, the accident pilot coordinated his next drop with the orbiting ATGS aircraft and then followed the ASM airplane. According to the ASM pilot, the ASM 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 to exit over descending terrain. The ASM 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." The ASM pilot 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 pilot 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 pilot was when he said, "OK," on the downwind and that this was not unusual. The crew of the ATGS airplane reported that, while Tanker 81 was on final approach for the drop, it appeared to strike trees with its left wing. Both aircrews reported that there was smoke in the area but that visibility along the approach to the drop was good. 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 to the drop site, 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 area below the cliff face. Tanker 81 was equipped with telemetry, which showed the airplane on a course heading of 253º at 4,810 ft msl and 148 knots at 1623. The flight telemetry log is included in the public docket for this report. PERSONNEL INFORMATION The pilot held an airline transport certificate with airplane multiengine land, airplane single-engine land, and instrument ratings. The pilot was issued a Federal Aviation Administration second-class medical certificate on February 12, 2014, with the limitation that he must wear corrective lenses. The pilot's flight records showed that he had 6,567 total flight hours. AIRCRAFT INFORMATION The airplane was originally a Grumman S-2 manufactured in 1966, but it was remanufactured as a Marsh Aviation S-2F3AT in 2004. It was equipped with two Honeywell (Allied Signal) TPE331-14GR turbine engines. Total airframe time since new was 5,819.5 hours as of October 2, 2014. The airplane was operated in the restricted category and maintained under annual and 100-hour inspections. The latest 100-hour inspection was completed on August 23, 2014. A review of maintenance logs showed no evidence of any airplane mechanical/maintenance anomalies. COMMUNICATIONS The pilot of Tanker 81 was in radio communication with either the fire base, the ATGS, or ASM throughout the accident flight. The pilot did not express any concerns about the flight or report any mechanical issues. METEOROLOGICAL INFORMATION At 1600, the closest official weather reporting station, about 7 miles northwest of the accident site, reported sky condition clear, temperature 75°F, dew point 32ºF, altimeter setting 29.90 inches of mercury, wind from 225º at 10 to 15 knots, and visibility greater than 10 miles. WRECKAGE AND IMPACT INFORMATION The airplane impacted trees and terrain on a steep, heavily vegetated area within the active fire zone. All the wreckage sustained impact and fire damage. The top of a tree had been severed and lay on the ground, and the outboard section of the left wing was found separated from the airplane. The inboard end of the separated wing section leading edge showed impact marks perpendicular to the wingspan. The inboard end of the wing section was torn chordwise from leading edge to trailing edge. Along the chordwise tear, the sheet-metal tears were jagged, and the internal structure was pulled apart. The tear was outboard of the locking mechanism that locked the folding wing in place. The aileron and flap were in place. The main fuselage, right wing, and both engines and their associated propellers were found in the river valley area below the cliff face. The wing-fold locking mechanism for the left wing's outboard section and the locking mechanism's locking devices, which were found in the "locked" position, were also located in the valley. The left-wing outboard section had separated outboard of the locking mechanism. Examination of both engines revealed impact signatures consistent with their producing power at the time of impact. All the propeller blades exhibited S-bending and torsional twisting. Portions of the blades were fragmented and exhibited leading edge gouging and chordwise scratching. Following the onsite examination, the wreckage was recovered to a secure facility and reexamined. No anomalies were noted with the airplane or engines. OPERATIONAL INFORMATION A review of the Interagency Aerial Supervision Guide (ASG), document PMS 505, NFES 002544, dated January 2014, Chapter 9, Tactical Aircraft Operations, outlines operational procedures for air tanker aircraft. Section 1, Low Level Operations, part b, item i defines a "show me" profile as a low-level pass made over the target using the physical location of the aircraft to demonstrate the line and start point of the retardant drop. The Show-Me Profile is normally used for the first airtanker on a specific run or when an incoming airtanker has not had the opportunity to observe the previous drop. A Show-Me can be used alone or before other profiles. The pilot [of the lead plane] begins the run when the airtanker crew can visually identify the aircraft, hazards, line, start and exit point of the drop. An NTSB Operations Group was formed, and the Operations Group Chairman's report is available in the public docket for this report. MEDICAL AND PATHOLOGICAL INFORMATION The Mariposa County, Coroner, Modesto, California conducted an autopsy on the pilot. The pilot's cause of death was attributed to "multiple blunt force injuries." The FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, conducted toxicological testing on specimens from the pilot. No toxicological anomalies were found.
The pilot's failure to maintain clearance from trees while maneuvering at a low altitude.
Source: NTSB Aviation Accident Database
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