Automatic Flight - Paravisual Display (PVD)

The PVD system provides the flight crew with a localizer-based lateral guidance display to steer the airplane to runway centerline during takeoff. The PVD system is used to augment visual cues available to the pilot during takeoff in low visibility conditions.

The system consists of a PVD Computer (PVDC) and two display units located on the glareshield. Each FCC provides data directly to the PVDC via its respective digital data bus.

The Captain's and First Officer's displays are controlled by their respective PVD ON/OFF switch. The FCC source for Captain's and First Officer's guidance is selected by the respective Flight Director Source Select switch.

Normal lateral guidance in low visibility conditions is taken from the visual observance of runway centerline lighting. If the Runway Visual Range (RVR) deteriorates during takeoff so that visual guidance can not be taken from the centerline lights, guidance is taken from the PVD until the centerline lights are re-acquired.

The PVD is active with the airplane on the ground, within valid localizer coverage and the PVD ON/OFF switch pushed ON. Outside of this coverage, the PVD remains shuttered.