GLOBAL DATA CENTER (GDC)
The Global Data Center (GDC) is a ground based computer facility
built and operated by AlliedSignal Aerospace for the purpose of pro-
viding flight planning, aviation weather, and message forwarding ser-
vices to AFIS operators on a subscription basis. The GDC communi-
cates with the operator via data quality telephone lines to a Personal
Computer as well as through the ACARS and satellite networks
directly to the aircraft in flight.
DATA TRANSFER UNIT (DTU)
The Data Transfer Unit (DTU) is a 3.5 inch micro floppy disk drive
mounted in the cockpit. Once the GNS-X
is switched on and the
disk inserted in the DTU, the AFIS Flight Plan and weather data are
transferred to and stored in the Data Management Unit.
DATA MANAGEMENT UNIT (DMU)
The Data Management Unit (DMU) computer formats the disk infor-
mation and presents it to the GNS-X
for display on the CDU.
The DMU also incorporates a data quality VHF transceiver. This
radio is tuned automatically by the DMU computer to the appropriate
ground station for the purpose of transmitting data to and receiving
data from the Global Data Center while in flight.
ANTENNA SWITCHING UNIT (ASU)
The Antenna Switching Unit (ASU) is required for those installations
where the DMU transceiver shares an existing VHF communications
antenna. The ASU switches the transmit side of the antenna
between the DMU data transmitter and the VHF voice transmitter.
During power up, the ASU defaults to the voice transmitter, if AFIS is
configured for a shared antenna. Pressing the AFIS annunciator on
the instrument panel switches the transmit side of the antenna to the
DMU data transmitter. Pressing the annunciator again, or pressing
the "push to talk" button on the VHF communications radio switches
the transmit side of the antenna back to the voice transmitter.
If AFIS is configured for non-shared antenna or there is no configura-
tion module, during power up the system will assume an antenna is
dedicated to AFIS.
Flight Management System AFIS Operation