Incident Summary
During the landing, the first officer failed to maintain the proper rate of descent, resulting in a hard landing on touchdown. Subsequently, during the landing rollout, the left main landing gear separated from the aircraft. The pilot-in-command stated that he knew the first officer was not going to make a good landing but did not take any corrective action beyond initially instructing the first officer to increase power.
Findings
Examination of the left main landing gear assembly revealed a preexisting crack in the outer cylinder housing. The hard landing and the preexisting crack contributed to the total failure and separation of the landing gear.
Probable Cause
The official probable cause is a preexisting crack on the left main landing gear outer cylinder housing and the first officer's failure to maintain the proper rate of descent, resulting in a hard landing on touchdown and subsequent total failure and separation of the left main landing gear on landing rollout. A contributing factor was the pilot-in-command's improper supervision of the first officer during the approach phase of the landing.