What happened
On 31 December 2007, a Cessna T3/03 Crusader, registration G-CYLS, was performing a private flight approaching Guernsey Airport from the north. The pilot executed a stable approach to Runway 27, following a right-hand base leg. During the approach, the pilot configured the aircraft with landing flaps and extended the landing gear, noting the expected mechanical sounds and trim changes. The pilot also confirmed the gear was down and locked via the cockpit indicators and a visual check in the landing gear mirror.
Upon touchdown just beyond the runway numbers, the nose landing gear suddenly failed. The aircraft's nose dropped, causing the propellers to strike the runway surface. The aircraft slid approximately 300 metres along the runway with the nose scraping the ground. The pilot, who was uninjured, was able to exit the aircraft through the rear door normally. The aircraft sustained substantial damage to the nose and propellers.
The investigation
The investigation focused on the mechanical failure of the nose gear actuator. While the pilot had observed green 'down and locked' indications, the nose gear continued to drop once weight was applied during landing. Examination of the aircraft revealed that the nose gear actuator's locking lugs had fractured, which allowed the gear to unlock and collapse forward.
Metallurgical analysis of the failed actuator showed that the fractures were the result of two distinct stages. One fracture was a secondary failure caused by ductile overload. However, the primary fracture was intergranular in nature and showed significant discoloration from corrosion products, suggesting the cracks had been present for some time. Investigators also noted that the grain orientation at the ends of the lugs was unfavourable, creating planes of weakness.
Findings
- The nose landing gear collapsed because the locking lugs of the nose gear actuator fractured.
- The primary fractures in the lugs were intergranular and showed evidence of long-term corrosion, indicating the cracks were not new.
- The mechanism that initially caused these cracks—potentially a heavy landing or rough ground handling during towing—could not be definitively determined.
- The grain orientation within the lugs provided a path for crack propagation.
- The aircraft manufacturer was aware of similar failures related to rough ground handling and noted that newer designs had removed a groove in the pin to reduce stress concentrations.