A common problem found during 12 Year Inspection, cracks around the windshield frames (6, 7 & 8) on both the left and right sides. In fact, these cracks are so common that Learjet makes an AAK (aircraft accessory kit) to repair the damaged area.
In the picture (right), you can see the right side frames 7 and 8. Frame 8 has already had the cracked section cut out and the doublers are held in place with clecoes. On this aircraft we had to repair left and right side frames 6, 7 & 8. It took one mechanic two full days to prepare the frame repairs. The assistance of another mechanic was required on the third day to finish the riveting.