Casualties unknown

Agricultural Aircraft Settles During Spray Run Preparation (N21861)

Three Forks, MT, US

On September 2, 1993, a Cessna A188B (registration N21861) operated by Ferguson, William R. was involved in an aviation accident near Three Forks, MT. Investigators recorded the probable cause as: The pilot's inability to maintain sufficient altitude during low-speed maneuvering in high density altitude conditions while carrying a heavy chemical load. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-06-10Data APIEditorial standards

An agricultural aircraft began to settle while maneuvering for a spray run at high density altitude. The pilot applied full power but could not prevent the incident, reporting no mechanical issues.

What happened

The incident occurred while an agricultural aircraft was maneuvering in preparation for a chemical spray run. During this phase of flight, the aircraft began to settle toward the ground. In response to the loss of altitude, the pilot applied full power to the engine. The pilot also jettisoned a portion of the chemical load, releasing approximately 30 to 40 gallons from the remaining capacity of 100 to 110 gallons.

Environmental conditions at the time included a density altitude of approximately 6,000 feet, which can significantly impact aircraft performance. The pilot reported that there were no mechanical malfunctions with the aircraft at the time of the event.

Probable cause

The pilot's inability to maintain sufficient altitude during low-speed maneuvering in high density altitude conditions while carrying a heavy chemical load.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001211X13473. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.