Two Mechanics; were informed a through bolt to secure the outboard flap torque tube to a flap actuator on a CRJ-900; had not been properly aligned with the splined shaft of a flap actuator.
Synopsis
Two Mechanics; were informed a through bolt to secure the outboard flap torque tube to a flap actuator on a CRJ-900; had not been properly aligned with the splined shaft of a flap actuator.
Narrative
Performing job card for Flap Tube Lubrication. I; RII'd (Required Inspection Item) the installation of the bolt; that secures the [torque] tube; to the [flap] actuator; right wing; outboard flap. Mr.'X' was the Mechanic performing the maintenance. All other flap [torque] tubes went on and were checked for proper installation; except this one. Mechanic 'X' was working on it for some time. The bolt could not be removed; without rotating the tube approximately 1/4 to 1/2 turn. I went into the MDC (Maintenance Diagnostic Computer) and rigged the flap brakes 'off' so the tube could be rotated enough to remove the bolt.The cleaning and greasing took place; and Mechanic 'X' was in the process of reinstalling the tube; but could not get the bolt hole; to align. Mechanic 'X' removed the shaft a few times; from the splines of the shafts; checked for proper alignment of the hole; but was unable to get the bolt to go through the shafts. It was suggested; by another Inspector; who had just stopped by; to clean the excessive grease; from the [flap] actuator and it's bolt hole. Mechanic 'X' did this; and aligned the shaft; and eventually; got the bolt to go through the hole. I inspected the shaft; put pulling force on shaft; and Mechanic 'X' secured the bolt. Not enough force used; and too much grease; possible hydro lock; of some sort. A road trip [was required]; replaced flap torque tube.Suggest [being] more forceful; and deliberate; with shaft movement; lateral and torsional.
Second reporter narrative
After cleaning and greasing I reinstalled the flap [torque] tube on the right wing outboard flap. I was having trouble getting the bolt hole lined up. I removed some of the excess grease from the [flap] actuator and was able to align the shaft and install the bolt. I pulled on the shaft [torque tube] it seemed to be secured. Mechanic 'Y' signed as the RII Inspector. Inspected and also did a pull check on the shaft. I then secured the bolt.I believe I used too much grease in the [flap] actuator; even after removing some of the grease it was still too much. I thought it was good it slid on the shaft farther and I thought the bolt went through the shaft. Should have pulled on it with more force and put a light coat of grease on the splines and that's all I should have done. I should have caught this. My Manager [notified me] about too much grease in the actuator; should be a light coating. A road trip out to ZZZ to secure or replace the flap drive shaft.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.