What happened
On February 16, 2015, an Aero Boero AB-115, registration PP-FHP, was performing a local instructional flight at Uberlândia Airport (SBUL) in Minas Gerais, Brazil. The flight was being conducted by an instructor and a student pilot.
As the aircraft began its takeoff roll and the tailwheel lifted off the ground, the instructor noticed a leftward yaw tendency. In an attempt to correct the aircraft's heading, the instructor applied right rudder. However, this input caused the aircraft to yaw rapidly to the right. Despite the instructor reducing engine power, the aircraft could not be maintained on the runway and veered off the pavement. The aircraft completed a rightward rotation, causing the left wingtip to contact the grass before coming to a stop 180 degrees from its original takeoff heading. The two occupants were uninjured, though the aircraft sustained minor damage to the left wingtip.
The investigation
The investigation examined the environmental conditions and the pilot's control inputs. It was noted that the aircraft has a known tendency to lose directional control during takeoff immediately after the tailwheel lifts, particularly in crosswind conditions. While the aircraft's manual specifies a 13kt crosswind limit, the flight school's internal safety policy reduces this limit to 10kt.
At the time of the event, the wind was reported as calm but highly variable. The investigation also noted that the air traffic control tower had planned to change the active runway following this departure. The investigators determined that the instructor's attempt to correct the initial leftward yaw with excessive right rudder, combined with the fluctuating wind, led to the uncontrollable rightward yaw.
Findings
- Excessive rudder input during the takeoff roll.
- Inexperience of the pilot in managing the aircraft's directional instability during wind fluctuations.
- High variability in wind direction and intensity during the takeoff phase.