Originally Posted by FlexibleResponse
Many years ago in my company we had a rogue L-1011 which occasionally had directional control problems on landing. After many write-ups it was eventually discovered that the No 2 Eng had the wrong part number reverser cascade vanes.
The normal configuration was for the No 1 and No 3 wing engines cascade vanes to be asymmetric handed (but mirror image) while the No 2 centre engine reverser cascade vanes were symmetric.
However the incident aircraft had a wing engine configuration fitted to the centre position but with the wing cascade vane part numbers incorrectly marked as centre vanes.
Now that took a little forensic science!
Actually this happened quite often. The first sign of something being wrong would be delamination, followed by desintegration, of the lower trailing edge horiziontal stabilizer panels, the panels just forward of the elevator. I remember Delta having this problem once in Shannon. They requested permision to replace the fiberglass panels with sheet aluminum on a temporary basis until they could order new panels and get the the plane to Atlanta for repair. About a week later they asked if they could again use aluminum sheet because ones they installed a week earlier were cracked. They had forgot to correct the cascades.