A retracted landing gear incident at Air Wisconsin Airlines has led the National Transportation Safety Board (NTSB) to conclude more on the job training is necessary for mechanics performing certain tasks.
The Bombardier CRJ on 14 December 2008 landed in Philadelphia with its left main landing gear retracted, which caused damage to the aircraft's left wing, aileron and flap.
During its investigation NTSB determined the aircraft underwent extensive maintenance that included the removal, replacement and visual inspection of the left and right main landing gear uplock assemblies.
Work performed on the assemblies was identified as a required inspection item (RII).
NTSB's investigation revealed that the mechanic who replaced the left uplock assembly had not completed uplock assembly work previously, received no on the job training for the task and was not supervised during the procedure.
The left uplock assembly, upper attachment bolt, nut and cotter pin assembly used to mount the left main landing gear to the structure were installed, but did not engage the uplock assembly. As a result the uplock assembly pivoted about to the lower bolt.
Since the upper attachment bolt didn't engage the uplock assembly, the left main landing gear remained in the up-and-locked position, and did not respond to pilot commands to lower prior to landing.
NTSB concluded the incident mechanic was not properly trained or supervised during the procedure, and the error was not detected by a supervisor.
The board states it is "concerned FAA does not currently require mechanics to receive on the job training or be supervised while performing RII tasks for the first time".
NTSB's investigation revealed that post maintenance inspections were not adequate to detect mis-rigging of the uplock assembly.
With the investigation complete NTSB has sent two recommendations to FAA. One is to require mechanics performing RII and other critical tasks receive on the job training or supervision when completing the task until the mechanic shows proficiency in that specific procedure. The second would require RII inspectors to receive supervision or on the job training on proper RII inspection until the individual demonstrates proficiency in completing inspections.
The board also reiterated three previous training recommendations it sent to FAA after other maintenance related accidents, including the January 2003 crash of an Air Midwest Beech 1900.