What happened
On February 15, 2009, an A-3/6 Bonanza, registration PR-RAF, was attempting to depart from an unregistered grass runway near Hotel Camalote, in Poconé, Mato Grosso. The flight was originally intended to proceed from Fazenda Nossa Senhora Auxiliadora to Poconé, but the pilot had performed an unplanned overnight stop at the grass strip due to heavy rain in the destination area.
Following a night of continuous rainfall, the grass runway was saturated and contained several puddles. During the takeoff roll, the pilot reached rotation speed; however, as the nose wheel lifted, the main landing gear sank into the soft, waterlogged terrain. This sudden increase in resistance caused a drastic loss of airspeed and lift. The aircraft lost control, veered to the left, and traveled approximately 65 meters into the adjacent woods. The three occupants (one pilot and two passengers) were uninjured, though the aircraft sustained severe damage to the left wing, landing gear, propeller, and fuselage.
The investigation
CENIPA investigators examined the aircraft's technical condition, the pilot's experience, and the environmental factors at the time of the accident. The investigation confirmed that the aircraft was airworthy and that the takeoff weight was within the limits for a dry grass runway. However, the presence of standing water and the soft nature of the soil significantly altered the takeoff performance.
Investigators also noted that while the pilot was highly experienced in the region and with various aircraft, he had limited experience with this specific model, having flown the A-36 Bonanza for only 40 hours and 30 minutes. The physical evidence, including the deformation of the propeller blades, indicated that the engine was producing thrust at the moment of impact with the ground.
Findings
- Impaired Judgment: The pilot's assessment of the takeoff feasibility was deficient, failing to account for the risks posed by the saturated runway conditions.
- Limited Type Experience: The pilot's relatively low experience with the A-36 Bonanza contributed to the outcome.
- Surface Conditions: The primary cause was the soft, waterlogged surface of the grass runway, which caused the landing gear to sink and induced a loss of airspeed during rotation.