Air Tractor AT502 N502RL accident near Bronson, Michigan

Probable cause

The pilot's failure to maintain airspeed while maneuvering, which resulted in exceedance of the airplane's critical angle of attack, an aerodynamic stall, and loss of control at an altitude too low for recovery.

NTSB analysis

The pilot was conducting an agricultural application flight in the turboprop-equipped airplane. Data from an onboard GPS unit showed that the airplane had completed 10 spray passes on a field, making right 180° turns after each pass to align the airplane for the subsequent pass. The airplane would climb between 500-700 ft during the first 90° of the turn, then descend during the second 90° of the turn. The airplane's groundspeed decayed to between 37 kts and 63 kts during the previous turns; however, the data did not capture the accident turn. A witness stated that he saw the airplane complete a spray pass, pull up into a near-vertical attitude, then become inverted. The airplane descended straight down and was starting to pull up when it hit the ground.

The airplane impacted terrain in a wings-level, nose-low attitude. No preimpact anomalies of the airframe, engine, or propeller were found. Based on the available evidence, it is likely that the pilot failed to maintain sufficient airspeed during a turn following a spray pass, which resulted in exceedance of the airplane's critical angle of attack, an aerodynamic stall, and loss of airplane control at an altitude too low for recovery.

Text from the NTSB. Open the NTSB docket for CEN18FA339 for the full record.