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Primary flight displays (PFDs)  often integrate all controls that allow modes to be entered for the autopilot. The PFD shown in Figure 4-2  offers knobs that allow you to enter modes without turning attention away from the primary flight instruments. Modes entered using the controls on a PFD are transferred to the autopilot. 

## Engagement of Autopilot Function 

Every autopilot offers a collection of buttons that allow you to choose and engage autopilot modes and functions. Buttons used to engage autopilot modes appear along the bottom of the autopilot shown in Figure 4-1. The system shown in Figure 4-3  does not use a separate device for autopilot controls; it integrates the autopilot function buttons into another cockpit display. 

## Verification of Autopilot Function Engagement 

It is very important to verify that an autopilot mode has engaged, and the aircraft is tracking the intended flight 

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