This January 2009 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Aircraft: Cessna 172RG. Injuries: None. Location: Carson City, Nev. Aircraft damage: Substantial.
What reportedly happened: As he was attempting to land, the pilot found that he was unable to fully extend the right main landing gear. Following multiple troubleshooting attempts he retracted the left and nose landing gear and performed a partial gear-up landing.
The post-accident examination revealed multiple fractures in the right main landing gear actuator housing and mechanical damage to the internal piston rack. Analysis of the fractures revealed that they had failed in overload. The manufacturer had released a service bulletin addressing repeated inspections for cracks at a specific location in the actuator body, a typical procedure for monitoring of fatigue cracks. Although it appeared that the owner had not complied with the service bulletin, the primary cracks were in a different location than those mentioned by the AD. The airplane also displayed features consistent with an overload event. The airplane had been used for flight training, and the overload failure of the actuator was likely caused by a prior hard landing. The investigation was unable to determine the initiating event.
Probable cause: The overload failure of the landing gear actuator at an undetermined time.
For more information: NTSB.gov