What happened
On April 7, 2013, a Piper PA-18, registration PP-GJI, was conducting an instructor training flight near Luziânia, Brazil. The flight, operated by Aeroclube de Brasília, involved an instructor and a student pilot performing touch-and-go maneuvers.
Following a three-point landing, the aircraft began to deviate significantly to the right during the landing roll. The crew attempted to correct the deviation by applying full left rudder, but the rudder remained ineffective due to the low ground speed. In an attempt to regain control and prevent the aircraft from exiting the runway, the instructor applied heavy left differential braking at approximately 3/5 knots. This sudden braking caused the aircraft to yaw sharply to the left. The momentum of this rapid correction caused the right wingtip to strike the runway and placed excessive lateral stress on the landing gear, resulting in the failure of the right main gear strut.
The investigation
CENIPA investigators examined the aircraft's mechanical condition and the environmental factors at the time of the accident. The investigation confirmed that the aircraft's airworthiness documentation, engine, and propeller logs were up to date. The weather conditions were favorable for visual flight, with nearly zero wind.
Investigators analyzed the tire pressures and the steering mechanism. While the main tires were within or slightly above recommended pressures, the nosewheel pressure was 24 psi, which was 6 psi below the manufacturer's recommendation of 30 psi. This lower pressure may have increased resistance between the nosewheel and the runway, complicating the alignment. Additionally, the investigation noted that because the rudder is not directly coupled to the nosewheel, the rudder's effectiveness was limited by the low speed of the aircraft during the rollout.
Findings
- The primary cause of the loss of control was the abrupt application of differential braking, which induced lateral instability and a sharp yaw.
- The initial deviation to the right may have been caused by a nosewheel misalignment during the three-point landing.
- The low pressure in the nosewheel tire (24 psi) may have increased ground resistance, making directional correction more difficult.
- The instructor and pilot were both uninjured in the accident.