What happened
On February 27, 2012, at approximately 19:15 UTC, a Piper PA-23-250, registration PT-CJX, was performing a local flight from the Bragança Paulista Aerodrome in São Paulo, Brazil. The aircraft was carrying a pilot and two passengers. During the landing circuit, the pilot deployed the landing gear; however, the green indicator light for the extended and locked position of the auxiliary gear failed to illuminate.
Believing the lack of indication was a known sensor error experienced in previous flights, the pilot performed a visual check of the auxiliary gear using the engine cowling mirror and proceeded with the landing. Upon touchdown and during the subsequent landing roll, the auxiliary gear retracted. The impact caused substantial damage to the propeller blades, the engines, and the forward section of the fuselage. All three occupants escaped the incident uninjured.
The investigation
The investigation focused on the failure of the landing gear indication and the subsequent retraction. Investigators determined that the failure of the green light to illuminate was caused by a misalignment of the microswitch responsible for indicating the gear's position. While ground tests using jacks showed the gear mechanisms and locking systems functioned normally during both normal and emergency cycles, the investigation could not definitively rule out hydraulic contamination or insufficient pressure as contributing factors. This uncertainty was compounded by the fact that the aircraft had been out of service in a maintenance shop for nearly a year prior to the incident, and there was a lack of specific maintenance records regarding the hydraulic system.
Findings
- The pilot, while highly experienced with 15,000 total flight hours, had less than five hours of experience specifically on this aircraft type.
- The landing gear microswitch was improperly adjusted, leading to the false indication.
- The pilot failed to follow emergency checklists or attempt the manual emergency gear extension procedure.
- The aircraft had been stationary in a maintenance facility for almost a year prior to its annual inspection.
- Inadequate pilot judgment regarding the gear indication and a lack of management oversight regarding maintenance documentation were identified as contributing factors.