A perspective view shows an object as it appears to an observer. [Figure 4-16A] It most closely resembles the way an object would look in a photograph. Because of perspective, some of the lines of an object are not parallel and therefore the actual angles and dimensions are not accurate.

An isometric view uses a combination of the views of an orthographic projection and tilts the object forward so that portions of all three views can be seen in one view. [Figure 4-16B] This provides the observer with a three-dimensional view of the object. Unlike a perspective drawing where lines converge and dimensions are not true, lines in an isometric drawing are parallel and dimensioned as they are in an orthographic projection.

An oblique view is like an isometric view, except for one distinct difference. In an oblique drawing, two of the three drawing axes are always at right angles to each other. [Figure 4-16C]

An exploded view drawing is a pictorial drawing of two or more parts that fit together as an assembly. The view shows the individual parts and their relative position to the other parts before they are assembled. [Figure 4-17]

Exploded view drawings are often used in IPCs that are used to order parts. The exploded view drawing has numbers and the numbers correspond to a list of part numbers. Exploded views are also used in Maintenance Instruction Manuals (MIM) for the assembly and repair of aircraft components. These drawings are often accompanied by notes that explain the assembly process.

A diagram may be defined as a graphic representation of an assembly or system, indicating the various parts and expressing the methods or principles of operation. There are many types of diagrams; however, those that the aviation mechanic is concerned with during the performance of their job may be grouped into four classes or types: installation, schematic, block, and wiring diagrams.

Figure 4-18 is an example of an installation diagram. This is a diagram of the installation of the flight guidance control components of an aircraft. It identifies each of the components in the systems and shows their location in the aircraft. Each number (1, 2, 3, and 4) on the detail shows the location of the individual flight guidance system components within the flight deck of the aircraft. Installation diagrams are used extensively in aircraft maintenance and repair manuals, and are invaluable in identifying and locating components and understanding the operation of various systems.

Schematic diagrams do not indicate the location of the individual components in the aircraft nor do they show the actual size and shape of the components, but rather locate components with respect to each other within the system. Schematics show the principle of operation of an aircraft system and are often used for troubleshooting and training purposes.

Figure 4-19 illustrates a schematic diagram of an aircraft air conditioning system. High-speed bleed air from the engine is

the lines that lead into and out of the unit. Schematic diagrams and installation diagrams are used extensively in aircraft manuals.