What happened
On June 21, 2013, an Aero Boero AB-115, registration PP-GOB, was performing a flight for pilot retraining at the Aeroclube de Goiás (SWNV) in Goiânia, Brazil. The flight involved an instructor and a student pilot operating under visual flight rules (VFR).
During the takeoff roll on runway 13, the aircraft reached a speed of approximately 30 knots and had traveled about 300 meters when it began to deviate from the runway centerline. The instructor had previously advised the pilot of moderate tailwind conditions with a left crosswind component. To maintain directional control at low speeds, the instructor had instructed the pilot to delay lifting the tail until reaching 40 mph, as conventional aircraft exhibit reduced rudder effectiveness while the tailwheel is on the ground.
However, the pilot lifted the tail at approximately 30 mph. In an attempt to correct the leftward drift, the pilot applied full right rudder. Simultaneously, the instructor applied the right brake to assist in directional control. This simultaneous application of opposing inputs caused the aircraft to yaw sharply to the right, leading it to exit the runway, climb a small embankment, and collide with a wire fence.
The investigation
The investigation conducted by SERIPA VI confirmed that both crew members held valid medical and technical certifications, and the aircraft was fully airworthy with up-to-date maintenance records. The investigation focused on the aerodynamic behavior of the aircraft during the takeoff roll under specific wind conditions and the conflicting control inputs applied by the crew.
Findings
- The primary cause of the excursion was the simultaneous application of right rudder by the pilot and right differential braking by the instructor, which induced a sudden yaw to the right.
- The aircraft's rudder effectiveness was insufficient to counteract the left crosswind component at the low speed maintained during the initial part of the takeoff roll.
- The aircraft sustained damage to its wings, fuselage, and propeller.
- Both occupants were uninjured.
Safety action
- The investigation authorities requested that the administration of the Aeroclube de Goiás implement a program for the leveling and maintenance of runway escape areas to improve safety during excursions.