What happened
On March 20, 2021, a Piper PA-18, registration PP-GKM, was performing a solo instructional flight at the Santo Ângelo Aerodrome (SBNM) in Rio Grande do Sul, Brazil. The aircraft, operated by Aeroclube de Santo Ângelo, was being flown by a student pilot undergoing training for a Private Pilot License.
During the landing phase, the aircraft experienced a series of uncontrolled vertical oscillations, known as porpoising, after a heavy touchdown. In an attempt to recover, the pilot applied maximum power to execute a go-around. However, the pilot failed to apply sufficient rudder compensation to counteract the engine torque and gyroscopic effects. This resulted in a sharp leftward yaw, causing the aircraft to veer off the left side of the runway. The aircraft traveled approximately 60 meters across the grass before striking a ditch, resulting in substantial damage to the landing gear and right wing. The pilot remained uninjured.
The investigation
CENIPA's investigation focused on the pilot's training progression and the flight school's oversight. While the aircraft was airworthy and within weight and balance limits, and weather conditions were favorable, investigators identified a significant gap in the pilot's training continuity. The student had not flown for approximately seven months prior to the accident. Although the flight school conducted two adaptation flights, investigators determined that this was insufficient to ensure competency after such a long hiatus. Furthermore, the student was cleared for a solo flight only one month after these brief adaptation sessions.
Findings
- The pilot had limited experience in the aircraft type.
- The student pilot had experienced a prolonged period of inactivity in flight training.
- The landing approach was unstabilized, leading to the initial porpoising event.
- Inadequate evaluation of the pilot's readiness by the flight school following the period of inactivity was the primary cause of the accident.
- Improper rudder application during the go-around allowed engine torque and P-factor to induce a sudden leftward deviation.