Oceanic Clearance Delivery

When incoming international aircraft approach North Atlantic airspace from the east or north, they need to be cleared for entry by the Gander Oceanic Control Center's Automated Air Traffic System (GAATS)—with a minimum of confusion and delay. Some aircraft avionics are not configured to receive the oceanic clearance messages over data link so the clearance is provided through voice communications. This can lead to misunderstandings, repeated requests for read-backs, and delays.

ARINC's Oceanic Clearance Delivery (OCD) system is designed to fix this potential problem by automatically converting the GAATS clearance messages into a data format that is recognized by the aircraft's avionics system. Properly equipped aircraft can request, receive, and acknowledge their oceanic flight clearances over data link.

First developed by ARINC in 1991, ARINC OCD establishes an interface between GAATS and the ARINC/Air Canada data link network. The interface allows the data link network to receive GAATS clearance messages, automatically reformat the messages into the proper format—ARINC 620 or 622/623—and then transmit the messages to the respective aircraft via the data link system. The crews can read their clearance messages on their cockpit monitors, print them, or store them for later retrieval. The OCD system—often referred to as OCP II—also maintains a history of each outstanding clearance, and correlates clearance rejects and read-backs.

The OCD system:

• Converts the GAATS clearance to match the aircraft's avionics format—ARINC 620 or 622/623
• Stores the request until the clearance is received from GAATS
• Notifies the aircraft if the request is received before the clearance message is issued from GAATS
• Sends the clearance message received from GAATS unsolicited to the aircraft, if the request was not received
• Converts the clearance acknowlegdement back to the proper GAATS format before delivery to GAATS

In addition, aircraft can access OCD from either the ARINC or SITA network and can receive the clearance via their secondary data link service provider if the clearance was undeliverable via their primary data link service provider. OCD is not limited to just the commercial airlines, but also will deliver clearances for general aviation and military flights.