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Sunday, February 1, 2004

Onboard File Servers

David Jensen


A third, and perhaps the most significant, revision to an ARINC standard is being hammered out by the Airline Electronic Engineering Committee's (AEEC's) Aircraft Network and File Server (ANFS) subcommittee. "Security is very important and a difficult subject to work with," says Paul Prisaznuk, senior principal engineer at ARINC Inc. He refers to a revision to accommodate a "security measure that would allow an onboard file server to be isolated adequately from the aircraft's avionics."

The revision would be to ARINC 763, which the AEEC first adopted in September 1999. The standard was established to apply to servers on board commercial aircraft, regardless of their applications.

File servers essentially are computers that store application and data files for workstations on a network. They exist in virtually all office environments and are becoming an important addition to business jets equipped to be "offices in the sky."

Aircraft file servers are distinct from ground-based servers, however, because they must be ruggedized and made to meet RTCA DO-160 specifications. They also must withstand temperature extremes.

Typically, file servers are installed on aircraft for the following purposes:

  • Passenger service, providing e-mail and Internet access, audio and video to passenger seats, wired or wireless.

  • Flight operations (with aircraft communications addressing and reporting system [ACARS] or satellite communications), sending and receiving operational documentation such as minimum equipment lists, weather, weight and balance calculations, passenger manifests, flight plans, and flight operations quality assurance (FOQA) data; and

  • Maintenance operations, providing software data loading and connection to the central maintenance system, which allows the ramp/line technician to use a laptop to access post-flight reports, wire diagrams and maintenance manuals.

With the latter two applications, the onboard file server renders the aircraft simply as a node in an airport or airline operations network infrastructure.

Since its adoption, ARINC 763 has been revised twice. In 2000 a revision was made involving a fiber optic interface to servers, allowing 1-gigabit/sec (Gbit/s) throughput. "We also added [standards criteria] for another Ethernet connection: 100baseT," says Prisaznuk. The revision accommodates the use of applications that require considerable bandwidth–largely graphics applications such as movies in the cabin and weather maps in the cockpit.

"In the second revision, we updated the gatelink definition for the wireless LAN access [to the server] to embrace the entire IEEE 802.11 family," he adds, referring to an Institute of Electrical and Electronics Engineers wireless standard.

The first draft of the third revision to ARINC 763 has been completed. Its primary focus is to establish a standard for the object request broker, or ORB, a link with a secure interface unit that isolates the commercial (or public access) server from the aircraft avionics. The ORB is comparable to a land-based firewall "but has very specific software," says Prisaznuk. He adds that the third revision will be completed "within six months."

An ORB is "used routinely in computers on the ground," Prisaznuk explains. "But an ORB in aircraft will have to be highly tailored, for example, to collect data from ARINC 429 data buses. You can't just take an off-the-shelf ORB."

The ANFS subcommittee also is rewording parts of ARINC 763 to accommodate the IEEE 802.11a wireless standard for local area networks (LANs) and gatelinks (airport wireless LANs), according to Prisaznuk. Thanks to the second revision, ARINC 763 applies the IEEE 802.11b wireless standard, which uses 2.4 GHz (or about 2 Gbits/s throughput). Now, in the third revision, it is being updated to apply IEEE 802.11a, which, oddly, did not precede 11b. The IEEE 802.1la standard is for a much faster, 5.8-GHz network, which has been demonstrating in early trials at up to 56-Mbits/s throughput.

Finally, the third revision to ARINC 763 will include a "total rewrite" of Attachment 12, titled "Considerations for Global Wireless LAN Operation." Attachment 12 defines considerations for airport wireless LAN implementation to enable universal connectivity.

Testing 763

ARINC 763 was proven to be a viable standard in 2002. It was tested in the full Airbus in-Flight Information Services (AFIS) system, which includes a wireless LAN, gatelink, server interface unit (SIU), avionics network server unit (ANSU) and cabin network server unit (CNSU), plus 20 wireless laptop computers. Tenzing provided the e-mail service. Route proving, held April 8-13, comprised 75 flight hours, including four long-range sectors, over a seven-day period. The aircraft was an A340-600, and crews participating in the trials were from Lufthansa and Virgin Air.

More than 2,000 passenger e-mails were sent during the AFIS trials. (The system can accommodate 20 users simultaneously.) In addition, maintenance documentation was e-mailed, and performance computation (takeoff, weight and balance) was calculated. The AFIS with an ARINC 763 architecture also included flight crew operations monitoring and an electronic cabin logbook.

As a result of the trials' success, Airbus now offers to its customers the AFIS system with an ARINC 763-certified file server. In addition to the A340-600, the system was scheduled to be approved on the A320, A330-200 and A340-300.

As part of its quest to "e-enable" its aircraft, Boeing, too, tested a system in 2002 that is comparable to the Airbus AFIS. Boeing Field has been wired to have both 2.4- and 5.8-GHz access points serving as gatelinks, and the manufacturer equipped a truck that serves as a "pseudo airplane," according to Jerry Price, wireless LAN technical project manager with Boeing Commercial Airplane Services. Moving the truck around the field, Boeing was able to determine if there was interference to either gatelink. Boeing was subsequently contracted to wire terminal 2 at Singapore's Changi airport for both 2.4- and 5.8-GHz gatelinks.

The U.S. airframer participates in ARINC 763 development but has "decided to take a slightly different route," says Price. Working with Rockwell Collins, Boeing is developing a network and file server system called Core Network. It is an "ARINC 763-like" system, he adds, but the components are rack-mounted rather than stand-alone line replaceable units (LRUs), making it more integrated.

Boeing seeks a more-simplified system to reduce its overhead, for example, by consolidating the airplane wiring interface. Core Network also is being designed to offer more flexibility. Instead of being a "box-oriented" system with shelves and racks for each unit, Core Network will allow the installation of much smaller network server cards.

Ultimately planned for the manufacturer's new 7E7, Core Network will probably first be offered in other Boeing models, according to Price.

Although Core Network diverges from the ARINC 763 architecture, Boeing hopes to have its specifications incorporated in the standard as a "viable alternative," says Price. "We plan to do that once we get the system on an airplane."

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