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(5) Fire Wall Stiffeners. - Figure 35 shows a typical repair which may be used for damage to the bulb angle stiffeners in the center of the bulkhead. (6) Fire Wall, - The stainless steel fire wall sheet should be patched with .015-inch gage stock of the same material using two rows or! AN442AD-4 rivets at 3/4-inch spacing completely around the damage for areas with in the bulkhead frame and one row gg 3/4-inch spacing for the area above the upper cross member. If the required rivet pattern cannot be obtained extend the patch to the edge of the original sheet or use inserts with conveniently located splices or frames of the same material. (See figure 36.) (7) Fittings. - All fittings and gussets on the firewall and also the engine mount and coolant tank supports must be replaced if either they or their attachments are damaged. d. Bulkheads Nos, 1A, 2, 3, and 4. - These bulkheads carry heavy axial loads caused by the diagonal tension in the skin between the upper and lower longerons and distribution of the loads from the wing to the fuselage. These bulkheads are heavily reinforced and, consequently, cannot be readily repaired. (See figure 15.) |
These bulkheads are heavily reinforced and, consequently, cannot be readily repaired. (See figure 15.) Due to their inherently low margins of safety, damage to these bulkheads or to their attachments cannot be neglected. In those cases where it appears feasible to repair minor damages instead of replacing the damaged parts. the table which follows may be used to determine the number of 3/16-inch A17ST rivets or 3/16-inch steel bolts to be used above and below the damaged area. In this table data is given separately for the back and for the inside flange of each upper channel, each lower channel and each flanged reinforcement. The data for the backs of the channels applies also to the flange which ls next to the skin and the data for the flanges applies to the corner or bent material at the junction of the inner flange and the back. Repair each damage with 24ST sheet of the same gage as the original. Divide the width of the damage, measured horizontally alter clean-up by the correct traction of an inch as given in the table to determine the number of rivets or bolts to used above and below the damage in attaching the repair material. Rivets should be used in preference to bolts where the number required is not excessive. If both the lower channel and reinforcement are damaged, each rivet or bolt may be used to attach the patches for both by placing the patches on opposite side so as to load the rivets or bolts in double shear. |
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*R=Rived Data B=Bold Data | |
Use existing holes or a minimum spacing of 3/4 inch for the above attachments. The stringer cut-outs are reinforced by the stringer clips which are designed to reinforce the bulkheads at the cut-outs. These fittings and their attachments as well as the fittings at the upper and lower ends qt the bulkheads must be replaced if damaged. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
