The first three paired elements correspond to ATA chapter, section and subject respectively. On the top level are ATA chapters, which deal with the different aircraft assemblies and systems such as chapter 79-Oil system which is the subject of the Cinegram prototype (cf. appendix I–Cinegram). The second number element refers to sections within chapters, e.g., 79-21 stands for Oil cooling. The third number element refers to subjects within sections, i.e. to separate components; e.g., 79 -21-51 stands for one of the coolers, the Air-oil heat exchanger.
On the top level are ATA chapters, which deal with the different aircraft assembly and systems
such as chapter 79-Oil system