CDM Hub System
The
CDM Hubsite, located at Volpe
National Transportation Systems Center, has the overall task of
integrating all available air traffic data and using it to predict future
airport demand. It then provides these predictions to the FAA and the
airlines in an Aggregate Demand List (ADL), which is read by Flight
Schedule Monitor (FSM), and then used by CDM participants to monitor
and analyze the data on future airport demand. The FAA Air Traffic Control
System Command Center uses this data to implement ground delay programs.
Data Flow
The hubsite at Volpe houses both the operational ETMS (Enhanced Traffic
Management System) and CDM strings used for CDM prototype operations.
("String" refers to the set of machines that do all the ETMS processing.)
Both strings receive airline schedule data from the Official Airline Guide
(OAG). On the CDM string, the flight data is loaded into the live database
fifteen hours before its scheduled departure. Both strings also receive
the NAS messages such as a flight plan (FZ), flight plan cancel (RZ),
departure (DZ), position update (TZ), and arrival (AZ). The demand predictions
are updated when any of these messages is received.
In addition, the
CDM string receives real-time schedule updates from the airlines. These
messages inform the CDM string when a flight is delayed, canceled, or
created, information which usually does not appear in the operational
ETMS. Some airlines send these messages over the ARINC teletype network,
while others send them over CDMnet When these
messages are received at the hubsite, they are incorporated into the databases
on the CDM strings and used to produce the ADLs. Features of the ADLs
include:
- Each ADL contains information on the flights that the CDM string predicts to arrive at an airport over the next 20 hours
- An updated ADL for an airport is generated and sent every five minutes.
- Each airline and FAA facility can register to receive ADLs for whatever airports it is interested in.
- An ADL is the data input for FSM.
- ADLs are sent over CDMnet.
