Loss of Control During Takeoff Involving Air Tractor AT-502B

Casualties unknown • VILA BELA DA SANTÍSSIMA TRINDADE, MT, BR

An Air Tractor AT-502B aircraft collided with fences and the ground during a takeoff attempt on a wet grass runway in Mato Grosso, Brazil.

What happened

On March 1, 2013, an AT-502B agricultural aircraft, registration PR-TPL, was performing a takeoff from a private grass runway at Fazenda Fortaleza do Guaporé, Mato Grosso. The aircraft began its takeoff run from an intermediate position on the 1,200-meter runway, utilizing only approximately 825 meters of available distance.

Shortly after becoming airborne, the aircraft lost altitude and struck a fence located 86 meters beyond the runway end. The aircraft then collided with a second fence post, causing significant damage to the left wing's leading edge and the empennage. The aircraft finally came to a stop 140 meters from the runway end. The pilot was uninjured and able to abandon the aircraft after shutting down the engine.

The investigation

CENIPA investigators examined the aircraft's configuration and the pilot's decision-making process. The investigation revealed that the aircraft's flaps were found in a 26-degree position after the impact. Investigators also identified an unapproved, non-standard flap control switch installed on the control stick, which was highly sensitive to touch.

Analysis of the performance data indicated that the takeoff weight was 3,061 kg and the runway surface was wet grass. According to the flight manual, the required takeoff distance to clear a 50-foot obstacle under similar conditions (dry paved runway) would have been approximately 877 meters. The investigation considered whether the pilot inadvertently activated the flap switch during the high-stress moments of rotation or collision, or if the pilot had intentionally used a high flap setting due to a prevailing professional culture among agricultural pilots.

Findings

  • The pilot's decision to use a shortened takeoff distance placed the aircraft outside its operational envelope.
  • The use of a wet grass runway further degraded the aircraft's performance.
  • An unapproved flap control switch installed on the control stick may have led to the inadvertent deployment of the flaps to 26 degrees.
  • A professional culture among some agricultural pilots regarding the use of high flap settings for takeoff may have influenced the pilot's actions.
  • The aircraft sustained substantial structural damage.

Probable cause

The accident was caused by the pilot's decision to initiate takeoff from a point on the runway that did not provide sufficient distance to clear obstacles, compounded by the degraded performance of the aircraft on a wet grass surface and the potential inadvertent deployment of flaps due to an unapproved control switch.

Frequently asked questions

What happened in the 2013-03-01 aircraft accident near VILA BELA DA SANTÍSSIMA TRINDADE, MT, BR?

An Air Tractor AT-502B aircraft collided with fences and the ground during a takeoff attempt on a wet grass runway in Mato Grosso, Brazil.

What aircraft was involved and where did it happen?

The accident on 2013-03-01 involved a aircraft, registration PRTPL, at VILA BELA DA SANTÍSSIMA TRINDADE, MT, BR.

What was the probable cause of the accident?

The accident was caused by the pilot's decision to initiate takeoff from a point on the runway that did not provide sufficient distance to clear obstacles, compounded by the degraded performance of the aircraft on a wet grass surface and the potential inadvertent deployment of flaps due to an unapproved control switch.

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