component appears. For example, the nose landing gear system appears in figure number 027-00. Group Assembly Parts List A group assembly parts list consists of a figure with its associated parts list. The illustration of a particular component is shown broken down into the detailed parts that make up the component. Each item in the illustration is numbered. A listing of parts in the assembly follows each illustration of the assembly. This parts list is in the same order as the part numbers shown in the illustration. The parts list gives the manufacturer’s part number of the part, its description, and other information. Figure 3-3 shows a typical IPB illustration. Figure 3-4 shows a listing of parts for the nose landing gear in figure 3-3. Use of the IPB When the Part Number Is Not Known At times, you will need to find a part number for an item that does not have the part number inscribed on it. Suppose you need a bracket assembly. You should be able to identify the following facts: What type of aircraft the component you are repairing is from The component the bracket was removed from The bureau number of the aircraft from which the component was removed For the purposes of this particular problem, assume that the nose landing gear strut was removed from an aircraft with Bureau Number 158620. If you follow the steps listed below, you can get a replacement part. 1. Obtain the landing gear IPB for the aircraft. 2. Refer to the alphabetical index of the IPB (fig. 3-2). 3. Locate the Nose Landing Gear Shock Strut, figure No. 027-00 (fig. 3-2). 4. Turn to figure 027-00 and look at the IPB illustration (fig. 3-3). Callout 2 of this illustration is for the nose landing gear strut. At this point, you should compare the old strut to the strut shown in the illustration. Select the desired part. In this case, callout 2 of figure 3-3 is the desired part. 5.   Refer to the parts listing for the illustration index number 2 (fig. 3-4). This index number establishes the relationship of the part in the illustration and the part in the list. It is for part number 2577818-011E<F, Strut NLG Shock, and it has a CAGE or manufacturer’s code of 55284. 6. Check the Use-On Code column to see if this strut is used on that particular aircraft, Bureau Number 158620. 7. Refer to the Usable-On codes list A at the foot of the list. 8. Have material control cross-reference the part number to its applicable NSN in the Master Cross-Reference List (MCRL) and verify it as a good number in the Management Data List Navy (ML-N). IPB Information Elements The following text is a detailed discussion of the various features found in the group assembly parts list in figure 3-4. Title (callout 1 in fig. 3-4). The title is on the first line under description. It describes what major component system is being broken down in the parts list. It is identical to the title in the illustration (fig. 3-3). Index number. As stated previously, this number (callout 2 of fig. 3-4) establishes the relationship between parts in the illustration and the corresponding parts list. Part number. The part number (callout 3 in fig. 3-4) is the manufacturer’s part number. Two other terms also may appear in this position, NO NUMBER and COMMERCIAL. The term no number indicates that the item has no assigned part number, but may have a model or type number that appears in the index. The term commercial in this column indicates that the item should be procured from a commercial source. Unit per assembly column. Refer to figure 3-4. There are three different types of codes that could appear in this column: 2, showing a specific quantity, shown by callout 4; AR, shown by callout 5; and REF shown by callout 6. Lets examine callouts 4, 5, and 6 in figure 3-4. In callout 4, the number designates the quantity used on a particular assembly. For example, there are two screws with part number MS27039-1-22. In callout 5, the abbreviations AR (as required) indicates a specific quantity has not been established for this part. The quantity necessary to achieve a desired result is used. NOTE: When the letters AR appear, no specific quantity is recommended. Sometimes, when 3-7