What happened
On February 4, 2008, at approximately 14:30 UTC, a Cessna A188B, registration PT-WNU, operated by Safra Aviação Agrícola Ltda, was performing an agricultural application flight near Cachoeira do Sul, Rio Grande do Sul. The aircraft departed from a temporary landing strip at Fazenda Barro Vermelho.
During the takeoff roll, the pilot noticed the aircraft was struggling to reach rotation speed and determined there was insufficient distance remaining to safely abort the takeoff. In an attempt to reduce weight, the pilot initiated the discharge of the agricultural load (urea). However, because the urea was granular, the discharge process was slower than with liquid products. As the aircraft crossed the end of the runway, it failed to gain enough altitude to clear existing obstacles and collided with wire fences located at the end of the strip. The aircraft sustained substantial damage to its wings, propeller, and fuselage, though the pilot remained uninjured.
The investigation
CENIPA's investigation established that the aircraft's airworthiness certificates were valid and maintenance had been performed by an approved workshop. The pilot was highly experienced, with 3,600 total flight hours and 1,000 hours in the Cessna A188B model.
While the aircraft was within its maximum takeoff weight limits, investigators noted that the takeoff performance calculations provided in the manual were based on hard surfaces and zero wind. The runway in use was grass, which increases rolling resistance. Furthermore, the investigation determined that the takeoff was performed with a tailwind component, as the prevailing wind was from 160° at 10 knots while the takeoff was from runway 30. The presence of wind gusts and turbulence further hindered the aircraft's ability to climb.
Findings
- The pilot failed to adequately consider wind conditions during the takeoff phase.
- The aircraft was unable to achieve sufficient lift to clear obstacles due to the tailwind and the nature of the grass runway.
- The discharge of granular urea was not instantaneous enough to mitigate the weight issues during the critical takeoff phase.
- Contributing factors included errors in pilot judgment, flight planning, decision-making processes, and a lack of adequate management supervision.