What happened
On February 7, 2012, a Piper PA-18A-150, registration PP-GKQ, was performing a local instructional flight at Jundiaí Aerodrome (SBJD) in São Paulo, Brazil. The flight, operated by Aeroclube Politécnico de Planadores, was conducting operational maintenance training with a pilot and one passenger on board.
During the second landing of the flight, the aircraft experienced a strong rightward yaw. The pilot attempted to correct the deviation and return to the runway centerline, but was unsuccessful. The aircraft exited the right side of the runway and entered a grassy area, where it subsequently nose-over. The impact caused substantial damage to the propeller blades, empennage, wings, and fuselage. Both occupants survived the event without injury.
The investigation
The investigation conducted by CENIPA focused on the mechanical integrity of the nose gear and the pilot's actions. Investigators determined that the nose wheel steering mechanism, controlled by the rudder pedal cables, had seized on the left arm, preventing the nose wheel from steering to the left. Upon disassembly, the component revealed small debris and wear on an internal flange. Because the component was not a sealed unit, this wear went undetected.
Regarding the maintenance program, the investigation found that the aircraft's maintenance plan only required lubrication for this specific mechanism, with repairs or replacements occurring only upon visual detection of non-conformities. No issues were found with the braking system.
In terms of flight dynamics, the investigation noted that the pilot applied the brakes abruptly during the excursion. In a conventional gear aircraft, if power is not reduced and brakes are applied sharply, the aircraft may undergo a forward pivoting motion around the main gear. The investigation concluded that the aircraft's entry into the grass was inevitable due to the mechanical failure, but the nose-over was caused by the sudden braking.
Findings
- The nose wheel steering mechanism experienced a mechanical jam on the left arm.
- Internal wear and debris within the non-sealed steering component contributed to the failure.
- The pilot's lack of experience and errors in judgment during the recovery attempt contributed to the severity of the excursion.
- The aircraft's maintenance plan did not include specific inspections for the steering mechanism beyond lubrication.