History of Flight
On August 20, 2009, at 1543 Pacific daylight time, an Air Tractor AT-802A single-engine air tanker (SEAT), registration 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. The airplane was owned by Minuteman Aerial Application, Inc. and operated by the BLM, U.S. Department of the Interior (DOI), 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), an aircraft operated by a supervisor controlling air assets. The supervisor instructed tankers on where to drop fire retardant. The pilot was assigned to drop retardant onto a saddle area between the intersection of two perpendicular ridgelines, to join the retardant coverage of two previous drops.
Multiple witnesses on the ground and in the air observed the accident airplane approach the drop area from the south. The airplane approached but did not release its load. Shortly thereafter, it made contact with rising terrain within the saddle, continued uphill while in contact with the ground toward a crest, then departed the end of the crest, descended, and collided with terrain in the valley below.
A witness on a ridge overlooking the saddle from the east observed another airplane make a drop along the ridgeline, estimating its altitude at about 200 feet above ground level (agl). Seconds later, the accident airplane flew a similar heading at a lower altitude. The witness noted concern as the airplane approached rising terrain, then disappeared behind the ridgeline. Seconds later, he saw it "launch" from the end of the ridgeline, "tumble", and collide with terrain below.
The ASM supervisor had just supervised a drop at the perpendicular ridgelines prior to the accident. He reported that the accident airplane was circling the drop area, and he relayed the position. The pilot stated he could see the drop area and did not require guidance. The pilot mentioned he could perform a salvo drop if necessary, but the supervisor replied it was unnecessary. The supervisor observed the airplane turn toward the final leg, pitch nose-down into the valley at a rate he considered excessive, then continue descending without releasing retardant. He saw the nose pitch up and the airplane "mush through the flair", then the underside made contact with terrain as it continued uphill. The left wing struck a tree, and the airplane spun around its nose, launched off the ridge, and collided with terrain below.
An impact-damaged Garmin 295 GPS receiver was recovered and sent to the NTSB for data extraction. The data revealed the flight sequence from Battle Mountain to the accident site. The airplane departed at 1510 on an outbound course of about 217 degrees magnetic. Over 22 minutes it climbed to about 8,800 feet (GPS). Approaching the drop area, it descended to about 7,800 feet and began a left orbit, flying over the intended drop point. During transition from downwind to base leg, it descended at about 700 fpm, continuing to the final leg on a heading of 350 degrees at an elevation of 6,889 feet. The final two GPS locations indicated descent rates of 1,632 and 2,136 fpm, with ground speeds of 139 and 145 mph.
After the accident, the ASM supervisor directed another SEAT to drop retardant in the originally designated area, which was accomplished successfully.
Personnel Information
A review of FAA airman records showed the 44-year-old pilot held an airline transport pilot certificate with multiengine land and single-engine land commercial privileges. He was issued a second-class medical certificate on April 27, 2009, with no limitations. He also held an Airframe and Powerplant mechanics certificate.
DOI aviation training records completed on March 11, 2009, indicated total pilot-in-command (PIC) time of 6,955 hours, including 512 hours in Airtanker/Dispensing Operations and 2,064 hours of Low Level Operations (<500 ft AGL).
Training documents from Minuteman Aerial Application showed the pilot completed a SEAT refresher course on May 18, 2009, covering target acquisition, entry, and exit.
On September 27, 2007, the pilot was involved in an incident with the accident airplane near Ogden, Utah. According to a DOI investigation, the left wing struck a tree during a retardant drop, causing external skin damage. The investigation concluded the pilot’s misunderstanding of contractual drop height and "target fixation" resulted in the tree strike, and that he showed poor judgment by not landing immediately but instead flying for 28 minutes over two suitable airports and a populated area.
On the accident day, the pilot reported for duty at 0900 and had dropped two prior loads of retardant 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 showed an annual inspection was completed on June 8, 2009, at a total airframe and engine time of 2,789.9 hours. The Hobbs meter at the accident site read 2,797.7 hours. At the annual inspection, the propeller had 455.8 hours since overhaul.
In May 2007, at 2,539.5 hours, the airplane was modified under STC SA00961CH with a Turbine Conversions Ltd. Dispersal Gate System (Fire Gate), commonly called the Hatfield Gate, approved by the Interagency Airtanker Board. The system comprises longitudinally hinged aluminum doors controlled by a cockpit master panel and a control stick trigger switch. It uses two hydraulic actuators driving gear racks. Hydraulic pressure is maintained by an independent electrically driven pump. An emergency backup accumulator and valves provide enough pressure to jettison the load via an emergency dump handle in the main cabin.
A representative from Minuteman Aerial Applications stated that the master panel had been modified with additional lamps and controls. An associate of the pilot, flying a similarly equipped airplane, reported that the pilot modified the arm switch and guard so that the guard and switch needed to be pulled downward to arm. He also noted it is not uncommon for pilots to inadvertently leave the master switch off, in which case the load can only be jettisoned using the emergency dump handle.
Meteorological Information
The closest aviation weather observation station was Derby Field Airport (KLOL), Lovelock, Nevada, 54 miles northwest. A METAR at 1553 PDT reported winds calm, visibility 10 miles, clear skies, temperature 104°F, dew point 21°F, altimeter 29.95 inHg.
The Desatoya Mountain (GRVN2) RAWS, elevation 6,200 feet, 34 miles south, reported at 1538 winds south-southeast at 22 mph, temperature 95°F, dew point 5°F. Based on 29.95 inHg, density altitude was about 9,700 feet.
Photographs taken after the accident revealed smoke trails indicating a wind direction out of the north.
Wreckage and Impact Information
The main accident site was at the northern edge of the Clan Alpine Mountains, about 34 miles northwest of Austin. Terrain was dirt and rocky with brush and trees 3 to 5 feet tall.
The first identified point of contact (FIPC) consisted of two 225-foot-long ground scars at about 6,450 ft msl, continuing uphill on a heading of 330 degrees. The spacing matched the main landing gear. Trees within the vicinity were severed at 4 feet. Seven 2-foot diagonal slash marks were observed between the scars 100 feet from the FIPC, correlating with rotating propeller blades. A twisted propeller blade tip fragment was found 20 feet west.
The scars continued to a crest at about 6,570 ft, then dropped. The main wreckage was 760 feet beyond the crest at about 6,460 ft. The debris path included left main landing gear and wing fragments.
The main wreckage area featured a 30-foot ground disruption on a heading of 350 degrees, followed by a 100-foot debris path to the fuselage, wings, and engine. The aft elevator push-pull tube and fragments of the fire gate doors and actuators were in the initial disruption. Fire retardant enveloped the site in a fan-shaped pattern forward of the initial disruption.
The engine remained attached to its mount. The propeller hub separated from the reduction gearbox and was found 20 feet beyond the main cabin. Two blades were separated at the hub, showing chordwise scratches, leading edge nicks, and axial twist. The propeller governor housing appeared fractured, exposing flyweights. The engine fuel control filter bowl was clear and full of fluid consistent with Jet-A.
Jet fuel odor was present throughout the site; all major sections were accounted for.
Medical and Pathological Information
Toxicological tests on pilot specimens by the FAA Civil Aeromedical Institute revealed no carbon monoxide, cyanide, or ethanol. Pseudoephedrine was detected in urine. An autopsy by the Washoe County Medical Examiner reported cause of death as multiple injuries due to blunt force trauma.
Tests and Research
Airframe
Examination at the accident site revealed a flap actuator jack screw dimension corresponding to a flap deployment of 24 ± 3 degrees. No pre-impact mechanical anomalies were identified with the airframe or flight control system.
Engine
The engine and accessories were examined at a Pratt and Whitney facility. The gas generator and accessory sections were largely intact. Exhaust ducts showed malleable crush deformation without pock marks. The compressor bleed valve was closed; its piston was coated with red material similar to fire retardant. Ingested soil was present on the inlet; first stage stator blades had small nicks consistent with soil ingestion. Rotating the compressor rotor by hand caused corresponding rotation of the compressor turbine and accessory gearbox. Combustion liner sections showed equidistant flame patterns. Vanes, shrouds, and blades throughout the compressor and turbine sections had circumferential rubbing and sooting. Reduction gears were free of defects; the second stage carrier shaft coupling showed torsional deformation. Chip detectors and filters were clear.
Fuel Control Unit (FCU)
The FCU sustained external damage and separated from the engine. The fuel pump passed acceptance tests. The condition lever assembly was damaged, preventing a full test; partial tests passed. Internal parts were free of defects.
No pre-impact mechanical anomalies were identified with the engine and FCU.
Dispersal Gate System
The fire gate system was fragmented. The forward and aft actuators were in the retracted position, correlating to closed hopper doors. The doors were crushed and separated. The control panel was partially affixed to the instrument panel; the master arm switch was off; the salvo switch was in trail; the gate opening size rotary switch was set to 4.
The hydraulic power pack had separated from its fittings. Hydraulic fluid was present in the reservoir and lines. The pump motor and housing separated; the plastic interconnect coupling was intact. The pump and motor moved freely. The pump circuit breaker was fragmented. The main accumulator appeared pressurized. Hydraulic supply and return lines separated at fittings; fracture surfaces were granular. Lines were free of splits, with residual fluid.
The emergency dump handle mechanism was fragmented; its position could not be determined. The emergency accumulator sustained external damage; it did not retain air pressure. Turbine Conversions Ltd. later tested an exemplar system simulating a ruptured accumulator, confirming the doors would open with a ruptured emergency accumulator.
Additional Information
Weight and Balance
Fueling records from Harless Aircraft Services at Battle Mountain Airport indicated the airplane was filled to its 254-gallon capacity with the addition of 177 gallons of Jet-A. The hopper was serviced with 707 gallons of fire retardant. The pilot’s weight was 275 pounds (from the medical examiner); about 50 pounds of baggage was in the cabin. The weight and balance sheet showed a basic empty weight of 7,011 pounds and a maximum gross weight of 16,000 pounds.
Airplane Flight Manual (AFM) Information
The FAA-approved AFM supplement onboard stated normal procedures: Prior to takeoff, arm system by turning switch on; select salvo drop level 4; verify pressure of 1500 PSI. After takeoff, turn system off at safe cruising altitude. At fire scene: select drop type; for trail drop verify level; for split drop verify timer; arm system; press and hold trigger switch; release and turn system off. The manual recommends reducing speed to 125-130 MPH and setting flaps to 10 degrees before a drop. Emergency procedures state that if the hopper load must be jettisoned without the electro-hydraulic system, the pilot should activate the ball valve handle marked “Firegate Emergency”.
Performance
Referencing the climb performance for the accident airplane configuration at 95°F, pressure altitude 6,500 ft, gross weight 10,000 lbs, and 10 degrees flaps, the rate of climb would be about 950 fpm. At 14,800 lbs, the rate of climb would be less than 200 fpm. The maximum takeoff weight at 4,000 ft field elevation and 102.2°F is 16,000 lbs.