What happened
During a training flight on a clear day, an Air Creebec Inc. Embraer 110P1, registration C-FPCU, experienced a partial collapse of its nose landing gear while landing on Runway 13 at Cochrane, Ontario. The aircraft, operated by a crew of two pilots, had been performing a simulated instrument flight rules approach before transitioning to a visual circuit.
Upon touchdown, the main landing gear functioned normally, and the nose gear was lowered without excessive force. However, during the landing roll, the nose gear assembly failed, causing the aircraft to veer toward the right edge of the runway. The pilot applied the left brake to prevent the aircraft from leaving the paved surface entirely, eventually regaining directional control and bringing the plane to a stop on the runway. The incident resulted in no injuries, though the aircraft sustained significant damage to the nose section, and the right propeller was damaged after striking a runway edge light.
The investigation
Investigators examined the nose gear assembly, which had been sent to the TSB Engineering Laboratory. The component, a part manufactured by ERAM, had previously been overhauled by an Australian company, Aeromil. It was discovered that the aircraft was fitted with an Australian Authorized Release Certificate that was not recognized by Transport Canada, as no maintenance agreement exists between the two nations.
Technical analysis of the fractured surfaces revealed that the failure of the strut housing occurred in a single-cycle ductile overstress mode. This failure was preceded by progressive fatigue cracks. The examination identified two distinct stages of crack growth: one area showed fresh fatigue striations, while an older section exhibited heavy oxidation and traces of a hardened bushing locking adhesive.
Findings
- The primary cause of the accident was the fracture of the oleo strut housing trunnion link arm.
- This fracture was initiated by a pre-existing fatigue crack within the bore of the link arm.
- The crack had propagated during the period before the component's overhaul and continued to grow during its service life on the aircraft.
- The fatigue crack went undetected during the overhaul process, though the specific reason for this oversight remains undetermined.
- Evidence of molybdenum disulfide within the bore suggests a gap had developed between the bushing and the bore, likely as the crack expanded during service.