inches to 15 inches) and different bezel controls. In normal operation, the display in front of the pilot is the PFD and will provide aircraft attitude, airspeed, altitude, vertical speed, heading, rate-of-turn, slip-and-skid, navigation, transponder, inset map view (containing map, traffic, and terrain information), and systems annunciation data. The second display, typically positioned to the right of the PFD, operates in MFD mode and provides engine instrumentation and a moving map display. The moving map can be replaced or overlaid by various other types of data, such as satellite weather, checklists, system information, waypoint information, weather sensor data, and traffic awareness information. Both displays provide redundant information regarding communications and navigation radio frequency settings even though each display is usually only paired with one GIA Integrated Avionics Unit. In the event of a single display failure, the remaining display will adopt a combined "reversionary mode" and automatically become a PFD combined with engine instrumentation data and other functions of the MFD. A red button labeled "reversionary mode" or "display backup," located on the GMA audio panel, is also available to the pilot to select this mode manually if desired. GMA audio panel The GMA panel provides buttons for selecting what audio sources are heard by each member of the cockpit. It also includes a button for forcing the integrated cockpit into its fail-safe reversionary mode. GMC/GCU remote controllers The GMC and GCU controllers are panel-mounted modules which provide a more intuitive interface for the pilot than that provided by the GDU. The GMC controls the G1000's autopilot, while the GCU is used to enter navigational data and control the GDU's functions. GIA integrated avionics unit The GIA unit is a combined communications and navigation radio, and also serves as the primary data aggregator for the G1000 system. It provides a two-way VHF communications transceiver, a VHF navigation receiver with glideslope, a GPS receiver, and a variety of supporting processors. Each unit is paired with a GDU display, which acts as a controlling unit. The GIA 63W, found on many newer G1000 installations, is an updated version of the older GIA 63 which includes Wide Area Augmentation System support. GDC air data computer The GDC computer replaces the internal components of the pitot-static system in traditional aircraft instrumentation. It measures airspeed, altitude, vertical speed, and outside air temperature. This data is then provided to all the displays and integrated avionics units.