What happened
On October 26, 2012, a Piper PA-34-200T aircraft, registration S5-DGL, was performing a flight for the purpose of a multi-engine piston (MEP) rating extension check. The flight was conducted under Visual Flight Rules (VFR) following a period of rainfall. The crew, consisting of a pilot candidate and a pilot examiner, performed a touch-and-go maneuver before attempting a full-stop landing on runway 31 at Divača Airport (LJDI).
The pilot touched down approximately 100 to 200 meters past the runway threshold. During the deceleration phase, the pilot noted poor braking effectiveness. Due to standing water on the runway surface, the aircraft experienced aquaplaning, leading to a loss of directional control and braking capability. As the pilot attempted to maintain the centerline and brake, the left landing gear strut experienced intense vibrations and asymmetrical braking forces. This resulted in the failure of the left landing gear support fitting. The aircraft veered off the paved surface, with the left propeller striking the asphalt and the left wingtip sliding along the edge of the runway. The aircraft eventually came to a halt on the grass, approximately 25 meters from the threshold of runway 13. The two crew members were uninjured.
The investigation
The investigation examined the aircraft's structural integrity, the condition of the landing gear, and the meteorological environment. Investigators analyzed the landing gear components, specifically the trunnion and support fittings, and commissioned a metallurgical analysis by the Institute for Metal Structures Ljubljana. The investigation also reviewed the runway conditions, noting that the crew was unaware of a recent NOTAM regarding the status of the asphalt runway due to administrative delays. The investigation confirmed that the landing gear systems were functioning correctly prior to the mechanical failure and that the pilot's medical and licensing credentials were valid.
Findings
- The primary cause of the accident was the sudden overload and failure of the left landing gear support fitting caused by asymmetrical braking during an aquaplaning event.
- The presence of significant standing water on the runway led to aquaplaning, which compromised directional control and increased the required stopping distance.
- The pilot's landing touchdown point was extended beyond the intended threshold.
- The crew was not aware of a relevant NOTAM regarding the runway surface due to incomplete administrative procedures.
- The heavy braking forces and resulting vibrations during the loss of control caused the structural failure of the gear support fitting and deformation of the shock absorbers.