What happened
On July 27, 2003, an EADS Socata TB 20 “Trinidad”, registration I-ODSO, was performing a landing at Treviso S. Angelo airport. The aircraft, operated by Aero Club “Ugo Capitan and” of Vicenza, was on a flight from Vicenza to Lussino, Croatia, with a scheduled stop in Treviso for customs clearance.
During the approach, the pilot noted that the green indicator light for the nose gear remained unlit, although the main gear lights functioned normally and the red warning light was off. Believing the issue was limited to the cockpit indication circuit, the pilot proceeded with the landing. Upon touchdown, the nose gear unexpectedly retracted, causing the propeller to strike the ground and the aircraft to slide along the runway. The pilot and passenger escaped the aircraft without injuries, though the aircraft sustained damage to the engine cowling, exhaust manifold, nose gear, and propeller blades.
The investigation
The ANSV investigation revealed that the aircraft had been flagged for a nose gear microswitch malfunction the previous day. The club's management had decided to continue using the aircraft despite this known issue, under the assumption that the fault only affected the cockpit light.
Technical examination of the wreckage showed that two of the three electrical wires in the nose gear down-limit microswitch wiring had broken. This breakage was caused by an improper installation path and the excessive tightening of a cable tie. This failure caused intermittent power interruptions to the hydraulic pump, which prevented the nose gear from completing its extension cycle.
Findings
- The primary cause of the accident was the failure of the nose gear microswitch wiring, which interrupted power to the hydraulic pump during the extension process.
- The aircraft was operated despite a known electrical fault in the gear indication system.
- The pilot did not perform any precautionary procedures, such as requesting a low pass over the runway, to verify the gear position despite the lack of a green light indication.
- The maintenance manual lacked detailed instructions regarding the correct installation of the microswitch wiring.
- There was evidence of management interference in technical operations, as the aircraft was cleared for flight without consulting technical personnel.