| Former or Bulkhead Repair The oval-shaped members of the fuselage are bulkheads. These members give form to the fuselage and maintain the shape of its structure. Formers or bulkheads are often called forming rings, body frames, belt frames, and similar names. Their purpose is to carry concentrated stress loads. Bulkhead damages are classified in the same manner as other damages. Specifications for each type of damage are given in the applicable manual for the aircraft. Bulkheads are identified with station numbers for ease in locating the damage area. The paragraphs that follow discuss repair categories and sheet metal stock strength. Repair Categories. Repairs to these members are generally placed in one of two categories: one-third or less of the cross-sectional area damaged or more than one-third of the cross-sectional area damaged. A patch plate, reinforcing angle, or both may be used if one-third or less of the cross-sectional area is damaged. First, clean out (trim) the damage and consult the applicable technical manual for details on how many rivets to use to establish the patch plate size. For the length of the break, use the depth of the cutout area plus the length of the flange. If more than one-third of the cross-sectional area is damaged, remove the entire section and make a splice repair. Consult the applicable technical manual for details on the splice repair and the number of rivets required. When removing the damaged section, be careful not to damage electric lines, plumbing, instruments, and so forth. Use a hand or rotary file, snips, or a drill to remove larger damages. To remove a complete section, use a hacksaw, key hole saw, drill, or snips. Sheet Stock Strength. Most repairs to bulkheads are made from flat sheet stock if repair parts are not available. When fabricating the repair from flat sheet, remember that the substitute material must have cross-sectional tensile, compressive, shear, and bearing strength equal to the original material. Never substitute material that is thinner or has a cross-sectional area less than the original material. Curved repair parts made from flat sheet stock must be in an annealed condition before forming and then must be heat-treated before installation.
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