What happened
On July 6, 2014, a Cessna 172D, registration PT-BVC, was performing a local flight departing from the Barra do Bugres Aerodrome (SWBB) in Mato Grosso, Brazil. The aircraft was operated by Aeroclube de Varzea Grande with one pilot and three passengers on board.
During the takeoff roll on runway 36, the pilot initially configured the flaps at 10°. Upon reaching a speed of 60 knots, the pilot commanded the flaps to 20°. Although the aircraft became airborne after reaching 65 knots, it failed to achieve sufficient climb performance to clear obstacles located at the end of the runway. In an attempt to abort the takeoff, the pilot reduced engine power. However, as the aircraft descended back toward the ground near the end of the runway, it struck a fence approximately 65 meters beyond the runway threshold, causing the aircraft to nose over. The impact resulted in substantial damage to the aircraft. One passenger sustained minor injuries, while the pilot and the remaining two passengers were uninjured.
The investigation
CENIPA investigators examined the aircraft's performance capabilities and the pilot's decision-making process. The investigation confirmed that the aircraft's takeoff weight was 998.41 kg, which was within the maximum allowable limit of 1,043 kg. Calculations based on the manufacturer's manual indicated that a successful takeoff clearing the 50ft obstacles was possible using a 10° flap setting.
Investigators also noted that the aircraft's flaps were found deflected at 30° during the initial investigation, despite the pilot's report of using 20°. Furthermore, the investigation established that the Barra do Bugres Aerodrome was officially closed at the time of the occurrence due to a lack of a basic protection zone plan, as per active NOTAM F1208/2014. The pilot's decision to operate at a closed airfield and the use of a flap setting not approved for takeoff by the manufacturer's manual were key focus areas of the analysis.
Findings
- Inadequate pilot judgment regarding the use of flap settings during takeoff.
- Improper flight planning, specifically regarding the operation at a closed aerodrome.
- The pilot utilized a flap deflection (20°) that increased drag and prevented the aircraft from achieving the necessary climb gradient to clear obstacles, contrary to the manufacturer's takeoff recommendations (0° or 10°).
- The operation was conducted in violation of Brazilian aeronautical regulations (RBHA 91.102 and 91.103) due to the use of a closed airfield.