What happened
On 9 September 2009, a Cessna 421, registration D-IIYY, was performing a charter flight from Aschaffenburg, Germany, to Groningen Airport Eelde. During the landing phase on runway 05, the aircraft's left main landing gear collapsed. This failure caused the aircraft to veer sharply to the left, sliding off the runway and coming to a stop in the grass on its left wing. There were no injuries to the two crew members on board, though the aircraft sustained serious damage.
The investigation
The investigation was based on information provided by the pilot in command and an initial damage assessment conducted by a maintenance service center. The crew reported that the landing gear had been selected down during the approach, with three green lights in the cockpit confirming the gear was down and locked. The flaps were fully extended at the time of the incident. Technical examination of the wreckage focused on the structural integrity of the landing gear assembly.
Findings
The investigation established that the outer tube of the left main landing gear had failed. This failure was characterized by crack growth within the outer tube, which significantly compromised its structural strength. Evidence suggests that the crack may have originated from internal pitting corrosion found on the tube. Ultimately, the mechanical load applied to the gear during the landing roll caused the weakened tube to fail, leading to the collapse of the landing gear.