History of Flight
On September 22, 2020, about 1830 mountain daylight time, an Air Tractor AT-802A, registration N836MM, was substantially damaged when it struck terrain near Emmett, Idaho. The pilot received fatal injuries. The airplane was operated as a public aircraft for firefighting.
Witnesses conducting firefighting operations observed the airplane descend and make an approach similar to previous single-engine air tankers (SEATs) dropping retardant. The airplane passed over a ridge and descended into a valley, but did not release retardant. A witness noted a brief application of engine power as the airplane began climbing over rising terrain. The airplane struck the terrain approximately 40 feet below the ridgeline.
A witness video captured the final seconds: the airplane descended over an intermediate ridge into a valley, momentarily leveled, then pitched up and impacted the ground.
The supervisor of the Air Tactical Group stated that prior to the accident flight, he briefed SEAT pilots on the target, coverage level, steepness of the drop, and rising terrain on exit. The accident airplane was cleared to make the drop and was on the correct line. It crossed the target ridge, descended into the valley, and passed the intended drop location without releasing retardant. The airplane initiated a climb but was unable to clear the opposite ridge.
GPS data from the NTSB showed the aircraft departed Ontario Municipal Airport, Oregon, at 1824, climbed to 5,500 ft mean sea level (msl), reached the fire area at 1837, performed left-hand circles, descended below 5,000 ft at 1843, and slowed from 140 to 120 knots calibrated airspeed. The last GPS point before impact was at 1845:44, at 3,235 ft msl, about 900 ft southwest of the accident site.
Personnel Information
Six months before the accident, the pilot was evaluated by the Office of Aviation Services (OAS) and carded as a Level II SEAT pilot, permitting missions in the fire traffic area (FTA). According to OAS, Level II pilots must inform the aerial supervisor of their status before entering the FTA.
Aircraft Information
The airplane was manufactured in 2020 and equipped with a Trotter Controls fire-retardant dispersal system (GEN III). The flight manual supplement for that system states: "DO NOT FLY UPSLOPE TO DUMP ON A FIRE. MAINTAIN SUFFICIENT ALTITUDE TO CLIMB AWAY IF DUMP IS ABORTED."
The operator reported a prior issue with the dispersal system: the pilot attempted to dump retardant, but nothing was jettisoned; a go-around and second attempt also failed. The pilot then used the red salvo button, and the load dispersed fully. The manufacturer provided a correction (disconnecting a cable from the firegate computer) which the pilot performed on August 21, 2020; no further anomalies were noted.
Wreckage and Impact Information
Examination by an FAA inspector showed the airplane struck the southwest side of a ridge about 40 ft below the ridgeline. The wreckage was in foothills with brush and grass; no trees, power lines, or towers were nearby. A debris path extended over the ridge into a ravine. Ground scars were consistent with left main landing gear impact followed by firegate doors. The main wreckage came to rest about 120 yards northeast of the initial scar on a heading of 040°. A small grass fire was near the engine, but no heat or fire damage was on the airplane. All major structural components were present.
Postaccident examination of the airframe and dispersal system revealed the cockpit and fuselage were mostly intact. The fire gate was separated with impact damage; the gearbox rotated freely, the electric motor was damaged. The emergency dump linkage was heavily damaged but remained attached; its position was consistent with the closed position. Electrical continuity was established from the battery bus to the firegate motor, and limit switches worked properly. Flight control continuity was established throughout; separations were impact- or recovery-related.
Additional Information
The FAA's Pilot’s Handbook of Aeronautical Knowledge discusses spatial disorientation, defined as lack of orientation with respect to position, attitude, or movement in space. Wright State University's article on visual perspective illusions notes that low-level flight can induce a "masked terrain illusion" when pilots rely on fixed horizontal cues like distant ridgelines that may appear as false horizons, potentially obscuring closer terrain.
Tests and Research
An airplane performance study used witness video and GPS data. The video captured the last 9 seconds of flight. GPS data showed the aircraft climbed to 5,500 ft, performed circles, then descended and slowed. The final GPS point (3,235 ft) was about 900 ft from terrain; the airplane was still descending. The study estimated aircraft weight at 14,000–15,000 lbs and climb rate about 700 ft/min (12 ft/s). The airplane climbed for about 3 seconds before impact, putting its minimum valley altitude at approximately 3,184 ft. Had the climb begun at the GPS point, it should have cleared the terrain, but the descent continued until 3 seconds before impact, too late to gain enough altitude. The video confirmed the late climb.