Six mechanics report about their involvement with a series of B757 brake build-ups that were later determined to have incorrect rivets installed holding the brake pads to the brake stators.
Synopsis
Six mechanics report about their involvement with a series of B757 brake build-ups that were later determined to have incorrect rivets installed holding the brake pads to the brake stators.
Narrative
My job assignment is riveting B757 stators; pressure plates and torque tubes. With brake pads; I am in training and have only been at this assignment for one month. I use an auto-riveter to complete this task. My job is to make sure pressure plates; torque tubes; and stators are flat checked before riveting. I was riveting B757 stators and pads. The machine (auto-riveter) was low on rivets [so] I got the part number from the Component Maintenance Manual (CMM) and went to the parts drawer (bin) and matched the number on the drawer to the number I had and filled the [auto-riveter] hopper.The way the drawers were set up and marked was confusing; I grabbed rivets from the bin (drawer) that I thought was marked with the part number I needed and continued riveting parts. After I rivet the stators; I check for proper seating of the pad onto the stator and check for any loose pads. The rivets that I had grabbed [from the drawer] were the wrong ones; I am still in training and still learning the job. The parts drawer has been changed now so that it is easier to distinguish the right rivet and is easier to identify.
Second reporter narrative
I am assigned to the B757 Brake build line. I build heat stacks and bolt-on brake carriers to heat stacks. While building heat stacks; I visually inspect stators only for obvious signs of defects. The diameter of the rivet that was used in this situation was not obvious by just looking at it without using dial calipers. The stators that are placed in my build area are labeled serviceable. It has never been standard build practice to check each rivet with a measuring device once it has been labeled serviceable and placed on the final assembly line. Pressure to produce due to upper management's production charts have placed personnel in a position to overlook this sort of thing.
NASA callback
Reporter stated he never added any rivets to the parts drawer; only removed rivets to fill the auto-riveter hopper. Somehow; similar looking but incorrect rivets were mixed into the parts drawer. One of the more experienced brake mechanics had noticed the differences in the rivet bucktails and that led to noticing the differences in the rivet head diameters. If you put the two types of rivets side by side; they look almost identical. Brake stators are bounced on the floor to see; or hear; if any pads are loose on the stators; which would mean the rivets were not installed correctly. Reporter stated his carrier pulled a whole series of brakes out of stores parts and removed many from their B757s to correct the problem. The parts drawer for the different types of rivets has been improved.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.