ACARS on the Net

By Charlotte Adams | September 1, 2001

For decades, major U.S. carriers have used the ARINC Inc. Airborne Communications Addressing and Reporting System (ACARS), a two-way VHF data link, to exchange operational messages with pilots on the tarmac and en route. Over the years, larger airlines have developed and fine-tuned in-house computer systems to receive, parse and distribute incoming messages and to format and transmit outgoing messages.

But smaller carriers have been left out in the communications cold. They have found it difficult to justify the large upfront investment necessary to manage the ACARS data link from their own operations centers. ARINC’s answer: a turnkey service bureau operation called OpCenter. Introduced last year, OpCenter, which uses a secure server at ARINC headquarters in Annapolis, Md., is part of the company’s SkySource family of Internet-based services.

All OpCenter customers need is a standard Netscape or Microsoft Web browser and a flexible, easy-to-use interface to log onto the password-protected server via the Internet. (ARINC provides dual-redundant servers for reliability.) Within an airline’s secure partition of the OpCenter server, dispatchers can read incoming messages from their aircrews and compose new messages for uplink. OpCenter also is interoperable with HF and satcom communications links for oceanic communications.

The OpCenter server is connected to ARINC’s worldwide, air/ground communications network, GLOBALink, and to the secure ground communications infrastructure, AviNet. These networks allow airlines to communicate with their aircraft worldwide and offer multiple pathways to airports via ARINC-managed data lines. The central processing system (CPS), the gateway between the ground infrastructure and the radio frequency (RF) link, is also dual-redundant, with additional remote backup.

OpCenter operates in real time, says Peter Wright, ARINC implementation manager. The dispatcher’s user interface looks like an e-mail program–an operator clicks on a message displayed on a summary page to call it up and read it. Users can copy paragraphs from weather reports or flight plans in Windows programs and paste them into the ACARS "window" to transmit as free-text ACARS messages.

OpCenter can receive and display out-off-on-in (OOOI) traffic indicating an aircraft’s gate departure, takeoff, landing and gate parking times, as well as its predeparture clearance and engine monitoring reports. The tool supports all air/ground and ground/ground ACARS formats.

ARINC’s first customer was Chicago Express Airlines, which operates connecting flights to midwestern cities for its parent, American Trans Air Inc. (ATA). Within the last six months, ARINC has added Gemini Air Cargo, Dulles, Va.; Vanguard Airlines, Kansas City, Kan.; and Polar Air Cargo of Long Beach, Calif., to its roster.

ARINC hopes to use OpCenter as a means of increasing the flexibility customers have to route ACARS information to specific airline systems, Wright says. Longer-term customers also could use OpCenter to upgrade their older ACARS computer systems or to provide backup processing. "It would be a cost-effective way to have an offsite backup that you can access by any Internet connection," he adds.

Chicago Express sees the product as an affordable way to manage data link information to and from its fleet of nine ACARS-equipped Saab 340s acquired from American Eagle last year. The airline plans to buy two more 340s and holds options on another three.

It’s less expensive to use the Internet as a message distribution channel than to build a system from scratch, says Capt. Scott Hall about OpCenter. Hall is Chicago Express’ vice president of operations. There’s a monthly message-hosting fee and a charge per message sent or received, he adds. Typically, a one-time implementation fee also is charged for an airline to begin using the service, says Wright.

Chicago Express uses the service bureau interface to send weather advisories, aircraft change-out information, and crew-scheduling messages. Flight crews receive predeparture clearances through OpCenter, which receives the information from the airport control tower. Chicago Express dispatchers can see pilot requests for Automatic Terminal Information Service (ATIS) data on wind and temperature, and on runways in use, Wright says. ARINC transmits the ATIS information to aircraft from its Air Traffic Services (ATS) server. OOOI times downlinked from the aircraft and crew messages regarding weather are stored and displayed on the OpCenter server.

The next step for Chicago Express will be engine trend reports for its maintenance department, an addition two to three months away, Hall estimates. The carrier also would like to use OpCenter to manage gate assignment information. But an automated means of receiving and viewing such messages is not yet available with OpCenter, according to ARINC.

Other enhancements are possible, adds Hall. Chicago Express would like to deliver ACARS messages to aircrew text pagers or text-capable cell phones via e-mail, he says, so crews can be alerted when their planes are inbound. "They don’t have to call dispatch and ask, ‘Is my aircraft there? Where is it?’"

ARINC is looking at forwarding messages by e-mail to other individuals within an airline, such as maintenance personnel. Wright says. The challenge is the logistics–questions such as what data, triggers and e-mail destinations.

Another idea might be putting an Internet kiosk in the crew lounge where messages could be read by crew members not equipped with text pagers, wireless handheld computers or cell phones.

ARINC also plans to make it easier for airlines to contact aircraft. A dispatcher wishing to send an ACARS message to a certain aircraft would click on an aircraft icon rather than enter the tail number manually, as is required now. This alternative ACARS interface would be available to airline OpCenter customers who subscribe to WebASD (Aircraft Situation Display), a related Web-based service that ARINC is integrating with OpCenter. ARINC expects to offer the icon-based interface by September 2001, says Teresa Anderson, senior program manager.

Plotting Turbulence

Another WebASD product is the "Northwest Airlines Turbulence Plot," which ARINC resells for Northwest. This electronic chart overlays turbulence graphics onto maps of North America, the Caribbean, North Atlantic, North Pacific, parts of Asia and Europe, and Australia and New Zealand.

Although this information is not now uplinked to aircraft, ARINC hopes to do so in the future. No timetable currently exists for the graphical weather upgrade, but the concept is to store a map in the avionics and then uplink turbulence updates.

However, a text-based version of the turbulence plot will be available for uplink over ACARS later this year, Anderson claims. The data could be uplinked to aircraft on the ground, with updates en route, although the service is envisioned primarily for preflight requirements.

ARINC also is developing a higher data rate (31.5-kilobit/sec.) link, as aviation evolves toward a Free Flight environment in which even routine communications will take place over data link. The current analog ACARS link, which will continue to be available, offers 2.4-kilobit/sec. throughput. VDL Mode 2 is available on the ground in the midwest and northwest United States and will be expanded this year, Wright says. ARINC is working with avionics vendors, airframe manufacturers and airlines to upgrade onboard equipment. Boeing plans to deliver aircraft with type-certified VDL Mode 2 avionics in October, and Airbus plans to do the same in 2002, ARINC says.

VDL Mode 2 is an Aeronautical Telecommunication Network-(ATN)-compliant subnetwork. The capability presently deployed is an interim step toward full ATN implementation, says Wright. VDL Mode 2 "will open the air/ground link to more features requiring higher bandwidth–larger messages such as graphical weather," he adds. However, compression algorithms available on ground-based digital applications can reduce a limited graphic file into a character string that can be uplinked over the current ACARS infrastructure.

Another SkySource service is WebAirport, which can uplink text-based terminal area weather forecasts and airport-specific meteorological observations over ACARS. These services, says ARINC, could become available as options to OpCenter.

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