Pilot Debrief

Air Tractor AT502 near Bronson, MI — 2018-08-18

Final reportCEN18FA339
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Date
2018-08-18
Location
Bronson, MI, USA
Aircraft
Air Tractor AT502
Registration
N502RL
Category
Airplane
Highest injury
Fatal
Fatalities
1
Phase of flight
Maneuvering

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 narrative

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.

Analysis

Primary failure mode
Loss of control
First missed decision gate
Pilot could have avoided excessive bank angle during the turn.

NTSB coding

Evidence available

  • ADS-B / radar
  • Photos
  • 8 docket documents
View NTSB final reportView NTSB docket

Docket documents8

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