WPR09GA407

The pilot’s failure to maintain a stabilized approach prior to the retardant drop and his subsequent failure to release the retardant load, resulting in a stall/mush and collision with terrain.

The pilot was dropping fire retardant onto a saddle area located between the intersection of two perpendicular ridge lines. One of several witnesses reported that the airplane circled the area and then began a steep descent towards the intended drop point. The pilot did not release the load of retardant over the drop area. The witness observed the nose of the airplane pitch up and “mush through the flare.” The underside of the airplane then made contact with rising terrain within the saddle and continued uphill on its main landing gear toward a crest where the terrain dropped away. It then descended and collided with terrain in the valley below. Postaccident examination did not reveal any anomalies with the airplane, engine, or retardant dispersal system that would have prevented operation. The dispersal system’s operating procedures recommend that it be turned off during flight to prevent inadvertent dumping of the load. According to other pilots it is not uncommon to forget to re-engage the system prior to the drop. The dispersal system included an emergency manual release mechanism that could be used in the event of a primary system failure or an inadvertent oversight by the pilot to turn the system on; however, impact damage prevented an accurate determination of the system's armed status prior to impact. Global Positioning System (GPS) information revealed an excessive rate of descent just prior to the expected drop, which corroborated witness accounts. Analysis of the accident location, with respect to the GPS data, density altitude, airplane load, and witness statements, would indicate that the airplane probably encountered a stall/mush at the drop area. The high density altitude and the airplane's flap settings would have diminished the climb performance considerably in its retardant loaded state. The airplane's continued trajectory after initial impact, as well as propeller witness marks and internal engine damage, indicated that the engine was producing power at the time of the accident.

HISTORY OF FLIGHT On August 20, 2009, at 1543 Pacific daylight time, an Air Tractor AT-802A, single-engine Air Tanker (SEAT) N807MA, Bureau of Land Management (BLM) designation T-857, collided with rising terrain during an attempted fire retardant drop at the Hoyt Fire, in the Clan Alpine Mountains, near Austin, Nevada. Minuteman Aerial Application, Inc., owned the airplane. The BLM, U.S. Department of the Interior (DOI), was operating the restricted category airplane as a public-use fire suppression flight. The pilot, the sole occupant, was killed. The airplane was substantially damaged by impact forces. The flight departed Battle Mountain Airport, Battle Mountain, Nevada, at 1513. Visual meteorological conditions prevailed, and a BLM flight plan had been filed. The BLM was utilizing an Airborne Aerial Supervision Module (ASM), which was an aircraft operated by a supervisor controlling the air assets working on the fire. The supervisor instructed the tankers on where to drop fire retardant. The pilot was assigned the task of dropping fire retardant onto a saddle area located between the intersection of two perpendicular ridgelines, thereby joining the retardant coverage of two previous drops. Multiple witnesses located both on the ground, and in the air, observed the accident airplane approach the designated drop area from the south. Their accounts describe the airplane approaching the drop area, but not releasing its load of retardant. Shortly thereafter, the airplane made contact with rising terrain within the saddle. The airplane continued uphill, while still in contact with the ground, towards a crest where the terrain dropped away. The airplane then departed the end of the crest, descended, and collided with terrain in the valley area below. A witness located on a ridge overlooking the saddle area from the east, observed another airplane make a drop along the ridgeline. He estimated the airplane to be flying about 200 feet above ground level (agl) when it made its drop. A few seconds later he observed the accident airplane fly along a similar heading, but at a lower altitude. He stated that he was immediately concerned because the airplane was approaching rising terrain. The airplane then disappeared behind the ridgeline, and out of his view. A few seconds later he observed the airplane, "launch" from the end of the ridgeline, "tumble" and collide with terrain below. The ASM Supervisor had just supervised the drop of retardant at the perpendicular ridgelines prior to the accident. He stated that the accident airplane was circling the drop area, and he relayed the position of the required drop to the pilot. The pilot reported that he could see the drop area, and did not require the ASM to guide him into position. The accident pilot stated that he could perform a salvo retardant drop if necessary, but the supervisor replied that this type of drop was not necessary. The supervisor then observed the airplane turn towards the final leg of the drop, and pitch nose-down into the valley at a rate he considered excessive for the terrain. The airplane then continued to descend, but did not release its retardant over the drop area. He then observed the nose of the airplane pitch up and the airplane, “mush through the flair.” The underside of the airplane then made contact with terrain as it continued up the hill. The left wing then struck a tree and the airplane spun around its nose, launched off the ridge, and collided with terrain below. An impact damaged Garmin 295 global positioning systems receiver (GPS) was recovered from the accident site. The unit was sent to the National Transportation Safety Board Office of Research and Engineering for data extraction. The data revealed the entire flight sequence, beginning at Battle Mountain, and continuing to the accident site. The GPS data revealed that the airplane departed Battle Mountain at 1510, on an outbound course of about 217 degrees magnetic, towards the direction of the fire. Over the next 22 minutes the airplane gradually climbed to an altitude of about 8,800 feet (GPS). As the airplane approached the drop area it descended to about 7,800 feet and began a circling left orbit; the last leg of which flew directly over the intended drop point. The airplane then began a left crosswind turn. During the transition from the downwind to base leg, it began to descend at an average rate of about 700 feet per minute (fpm). The airplane continued the descent through to the final leg, which was in line with the drop area, on a heading of 350 degrees and an elevation of 6,889 feet. The final two GPS locations prior to reaching the impact area corresponded to a descent rate of 1,632 and 2,136 fpm, with ground speeds of 139 and 145 mph, respectively. After the accident, the ASM supervisor directed another SEAT to drop retardant in the area originally designated for the accident flight. The retardant was applied successfully. PERSONNEL INFORMATION A review of FAA airman records revealed that the 44-year-old pilot held an airline transport pilot certificate with ratings for airplane multiengine land, and commercial privileges for airplane single-engine land. The pilot was issued a second-class medical certificate on April 27, 2009, with no limitations or waivers. The pilot additionally held an Airframe and Powerplant mechanics certificate. DOI aviation management training records, completed by the pilot on March 11, 2009, indicated a total pilot-in-command (PIC) time of 6,955 flight hours. At that time he reported a total PIC flight time of 512 hours in Airtanker/Dispensing Operations, and 2,064 hours of Low Level Operations (<500’AGL). Training documents provided by Minuteman Aerial Application, Inc., revealed that the pilot completed a SEAT refresher course on May 18, 2009. This course included flight instruction in target acquisition, target entry, and target exit. On September 27, 2007, the pilot was involved in an incident with the accident airplane near Ogden, Utah. According to the DOI, who investigated this event, the left wing of the airplane struck a tree during a retardant drop. The wing sustained visible external damage to its skin during the sequence. Analysis by the DOI resulted in a conclusion that the pilot’s misunderstanding of the contractual drop height, along with “target fixation” resulted in the tree strike. Additionally, the investigation determined that the pilot showed poor judgment by not landing immediately after the collision, but instead returning to his base, and in the process flying for an additional 28 minutes over two suitable airports, and a heavily populated metropolitan area. On the day of the accident, the pilot reported for duty at 0900. He had dropped two prior loads of retardant on the fire earlier in the day using the accident airplane. AIRCRAFT INFORMATION The low-wing, tailwheel equipped, fixed-gear airplane, was manufactured in 2003. It was powered by a Pratt and Whitney PT6A-67AG turboprop engine, driving a Hartzell 5 blade constant-speed propeller. Additional equipment included an 800 gallon hopper, and an emergency fuel control override system. Maintenance records indicated that an annual inspection was completed on June 8, 2009, at a total airframe and engine time of 2,789.9 flight hours. The recorded time on the Hobbs hour meter at the accident site was 2,797.7. At the time of the annual inspection the propeller had accumulated a total time since overhaul of 455.8 flight hours. Dispersal Gate System In May 2007, at a total airframe time of 2,539.5 hours, the airplane had been modified in accordance with Supplemental Type Certificate (STC), SA00961CH, by the addition of a Turbine Conversions Ltd., Dispersal Gate System (Fire Gate). Commonly referred to as the ‘Hatfield Gate’, this system had been approved for use by the Interagency Airtanker Board. The Hatfield Gate is retrofitted to the