NTSB Identification: WPR09GA407
14 CFR Public Use
Accident occurred Thursday, August 20, 2009 in Austin, NV
Probable Cause Approval Date: 07/01/2010
Aircraft: AIR TRACTOR AT-802A, registration: N807MA
Injuries: 1 Fatal.

: NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this public aircraft accident report.

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.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

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.

Full narrative available

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