A publication of the National Air Traffic Controllers Association
Issue link: http://natca.uberflip.com/i/820602
Last week , Controller Pilot Data Link Communication (CPDLC) sites se nt over 4060 clearances a day. There are many different entities and systems that must work togethe r to ensure that a CPDLC clearance is delivered. The process begins when the Airline Operations Center (AOC) files a flight plan. This is the same flight plan information that the pilot loads into their Flight Management System (FMS) before they receive th eir clearance from the controller. This flight plan is added into the local ERAM flight d ata approximately two hours prior to the P - Time. Just prior to the strip printing in a tower, ERAM will check the routing and verify that it meets the current adapta tion for routing. If it does not, when the strip prints it will include an Adapted Departure Routing (ADR) or Adapted Departure Arrival Routing (ADAR). This is the between the plusses routing that you see on the strip. When the strip prints in the tower, E RAM send a message over the TDLS ERAM Direct Connect (TEDC) interface to the Tower Data Link Services (TDLS) system. This information not only has the flight plan information, it also includes whether the aircraft is requesting a Pre - Departure Clearance (P DC), CPDLC , or neither. At the same time the controller is receiving the flight data, the pilot is logging on to the DataComm Network Service (DCNS). ERAM has two facilities located at ZLC and ZTL that are known as the National Application Processor (NAP) Realm. The NAP Realm maintains log on information for all the aircraft across the nation and one of these sites are the active site with the other being in back up. When the pilot is getting ready for departure, they will log onto the network. The network includes everything outside of the FAA demarcation area such as the Antennas on the airport and the network processing sites for Rockwell Collins (form erly known as ARINC) and SITA. The pilot logs on by typing into the ATC Comm page of the FMS their Fli ght ID, tail number and departure airport. This information must match exactly with a flight plan in ERAM for the log on to be accepted. Once the logon is accepted, the clearance will be sent to the aircraft once the controller processes it. TDLS will dis play the clearance to the controller when ERAM sends the flight data. The controller then populates the correct information into the clearance and selects send. When the controller pushes send, the system will send a separate message to the AOC asking for gate information for that flight. TDLS will also send a message to ERAM asking if it has logon information for that flight. If the pilot has logged on, the system will begin to make virtual connection with the aircraft, and if they have not logged on, the flight information will wait in TDLS until ERAM passes along the log on information. When TDLS receives the logon information it sends a message through the DCNS to the aircraft requesting to connect. The avionics system under the covers will answer the r equest with a conformation and send it back to TDLS, which creates a session between that aircraft and TDLS. The two can now send information back and forth. Once the session is created, TDLS will send the clearance to the aircraft. TDLS determines what it will send to the flight deck based on what the airline filed and if any changes were made by ERAM. If no changes were made to the routing, the aircraft receives a Cleared as Filed (CAF). If changes were made to route either by TMU (a revision) or by and A DR/ADAR, TDLS will send the new route information up to the point of the change and then the aircraft gets a then as filed. When the clearance is uplinked to the aircraft, TDLS will also send the information in the clearance to the AOC to keep them up to d ate on changes.