You have several steps to take to find the correct repair materials and procedures in a structural repair manual. Figure 13-57 shows each of the steps. NOTE: The aircraft structural repair manual, shown in figure 13-57, was selected as a typical manual. The procedures that follow are typical but are not standard. Various manufacturers use different methods to indicate the types of materials used and special instructions for using their particular manual. 1. The extent of the damage to the aircraft is determined by the inspection of the damaged area, as previously explained. 2. Using a master index damaged group of the aircraft. on the diagram, determine the where the component is found. diagram, identify the From the table shown section of the manual 3. After locating the correct group master index diagram, obtain the correct item number for the damaged component from the illustration. 4. Find the index number for the damaged unit from the component diagram. 5. The index number is (hen matched with the item number on the repair material chart. This chart will normally give the part’s description, drawing number, gauge, type of material, and location of repair diagram. 6. You can find the repair diagram by locating the required section of the manual and turning to the correct figure in that section. Access provisions and negligible damage information are given on the repair diagrams. After the damage has been cleaned, determine whether or not the damage is negligible according to the repair diagram. If the damage is within the limits of negligible damage, it may be disregarded unless it is necessary to close the hole for aerodynamic smoothness. If the damage exceeds the limits of negligible damage, it must be repaired according to the repair diagram or replaced. Layout for Repair Information needed to fabricate replacement parts is usually found on blueprints, while information concerning repairs may be found in the aircraft structural repair manual. The manual contains information on extrusions and the necessary data for the fabrication of various sheet metal equivalents. The aircraft structural repair manual will indicate the type of material to be used in each repair. If the correct material is not available, the General Manual for Structural Repair should be checked for an acceptable substitute. The fabrication of sheet metal parts for internal structural repair requires careful adherence to the accepted standards of aircraft sheet metal work. This includes accurate calculation of bend allowance and careful layout of all dimensions. Layout is the interpreting and transcribing of information from blueprints, drawings, or written instructions to the metal that will be made into a part for an aircraft. If several parts are to be fabricated, the dimensions may be transferred to a template. Working from a template ensures a higher degree of uniformity and speeds production. The procedure for making a layout either for a template or for the actual part is essentially the same. Layout of a part or a template consists principally of marking the flat sheet so that all drilling, cutting, bending, and forming operations are indicated on the sheet. It is a comparable level 3 drawing that has been marked up in sufficient detail to clearly indicate the fabrication requirements for each piece/part. The sheet metal layout may be made from printed instructions, but it is more often made directly from the blueprint. Accuracy in all details is essential. You should not transfer dimensions directly from the blueprint to the layout because the print material may have stretched or shrunk, which causes minor distor- tion of the dimensions. Measurements indicated on the blueprint are made on the layout. Details are often left out and must be developed in the shop. You may, for example, find that you must add several dimensions, and then figure the bend allowance for the material consumed in each bend before you are able to lay out the overall length or width of a part. On very accurate layouts, a magnifying glass is frequently used as an aid to precision work. A magnifying glass enlarges the graduations on a scale and makes them easier to read. It helps locate center punch marks, and it allows a close inspection of the accuracy of the completed layout. Earlier in this chapter, we discussed the layout procedures for sheet metal fabrication. These same procedures are used to lay out the material that is going to be used to make the repair. 13-40