What happened
On July 8, 2018, a Siai Marchetti F.260 C, registration HB-EWQ, was performing a private flight from Locarno to Lommis. Following a routine landing on the grass runway 06 at Lommis, the pilot taxied the aircraft off the runway. During this taxi phase, the retractable nose landing gear suddenly collapsed. While the pilot and one passenger were not injured, the aircraft sustained light damage, specifically to the propeller and the mechanical nose gear control unit.
The investigation
Investigators examined the nose gear assembly and discovered significant structural failures. A maintenance inspection revealed a broken rod end on the nose gear control rod, which is attached to the control bell crank. Additionally, the eye bolt on the rear drag brace had been bent forward. The investigation also found that all attachment point bearings for the nose gear exhibited excessive play. \nReview of maintenance records showed that these issues were not new. Previous inspections, including a 50-hour inspection in April 2018 and a 100-hour/annual inspection in August 2017, had explicitly listed significant play in the nose gear bearings and a leaking nose gear shock absorber as open items. Although some bearings were replaced during repairs just days before the accident, the records indicated that the excessive play in the knee joint bearings remained unaddressed.
Findings
- The nose gear locking mechanism likely failed to remain properly engaged due to excessive play in critical bearings.
- The uneven surface of the grass runway likely contributed to the disengagement of the locking mechanism.
- Maintenance deficiencies had persisted for at least one year prior to the incident.
- There was a failure to consistently rectify known safety-critical defects during scheduled maintenance intervals.