[Avionics Today 08-05-2015] SITA OnAir is working on different methods to augment support for the communications that occur daily on its worldwide air-to-ground Aircraft Communications Addressing and Reporting System (ACARS) services network. While the communications traffic on the network has certainly increased since airlines started its widespread use in the 1980s, the air transport communications and information technology provider is not worried about congestion on the network, yet.
ACARS Coverage map. Photo: SITA.
Today, more than 14,000 aircraft connect to SITA OnAir's ground station Very High Frequency (VHF) radios at nearly 900 airports around the world, according to Paul Gibson, aircraft solution line portfolio director at SITA OnAir. Over the last two decades, ACARS has remained the aviation communications backbone for the majority of the world’s airlines. However, Gibson said the company is directly addressing any concerns about network congestion.
"The number of messages generated per aircraft, has increased for sure," said Gibson.
SITA OnAir's ACARS services use VHF radio technology over land to enable the exchange of safety services and Aeronautical Operational Control (AOC) messages between flight crews and airline flight dispatch departments, as well as Air Traffic Control (ATC). Gibson said SITA is constantly monitoring any necessary increases in capacity for various areas of the network that appear to become congested.
"If we know there is a significant number of aircraft trying to communicate at a particular airport, for example, then we would just put more capacity there in terms of the network and the radios," said Gibson. "With the VHF technology, there is a theoretical limit on how many aircraft can be connected to a single radio at a time. So, we need to manage that and make sure we have enough capacity where we need it."
One way that SITA OnAir is currently augmenting the existing ACARS network is with Automatic Dependent Surveillance Broadcast (ADS-B) technology.
“One of the things we’re currently focusing on is integrating ADS-B technology into our operations. That allows us to use ACARS to track the aircraft without significantly increasing the traffic on the network because we can effectively switch to ADS-B, which is a different technology over land where that’s available,” said Gibson. “That’s one way where we’re providing the airlines that service without increasing significantly the number of ACARS messages that they need to handle.”
In the future though, SITA will look at the use of other communications links, such as Internet Protocol (IP), as well as a possible increased usage of satellite networks, which are currently reserved for when aircraft are out of range of ground stations, primarily flying over water.
"In terms of the future, what we see is that the aircraft now are being equipped with more advanced communications links that provide [Transmission Control Protocol/Internet Protocol] TCP/IP type connectivity that passengers use. Most of the domestic U.S. aircraft today provide Internet access to the passengers sitting in the cabins. And we definitely see in the future those kinds of technologies will be used more in the cockpit as well," said Gibson.
Other major industry players see ACARS over IP as a future possibility as well. Rockwell Collins' recently released e-book, "Harnessing the Power of Aviation's Information Age," states that, by 2030, the number of active air transport and business aircraft is expected to grow to nearly 85,000, with 80 percent of those equipped with new information-enabled systems.
"ACARS over IP, is designed to utilize higher-speed broadband channels, allowing support of the iPad and other smart devices. This creates the opportunity to connect Internet-enabled devices to cockpit avionics in order to efficiently update navigation databases and transfer flight plans," Yun Chong, vice president, commercial aviation solutions and information management services, and Alexis Hickox, senior director of strategic development, information management services, wrote in the new Rockwell Collins e-book.
Cobham Satcom is currently participating in an ongoing FAA-supervised technology demonstration with Hawaiian Airlines
. The ongoing flight trial features Hawaiian's Boeing 767s equipped with Cobham's Aviator S satellite communications system to enable the transfer of ACARS data messages over SwiftBroadband.
Gibson said one of the main issues with the inevitable move to ACARS over IP will be cyber security. As it stands today, SITA OnAir's air-to-ground ACARS services network is not exposed to any IP connectivity.
"The avionics that receive and send the ACARS messages are completely isolated from anything in the cabin," he said. "How do we connect in some of the newer IP technologies without adding any security risks? That’s one of the things that we’re looking at for the future."