Keeping in touch

ACARS was introduced by US company ARINC in 1978, developing the system architecture and operational protocols that govern the use of ACARS systems globally.

Initially, ACARS transmitted via VHF ground stations, but increasingly relies on satellite communications to provide global coverage, unhampered as SATCOM is by VHF’s range limitations.

The heart of the datalink system on board the Jetstar A320-232 is the ACARS management unit (MU).

Through this, data is routed, then transmitted via air to ground network. Information sent to the aircraft is displayed either on its FMS, a cockpit printer or a cabin terminal. Data sent from the aircraft goes to a central point, in Jetstar’s case, its operations centre, and is then distributed to its intended recipient.

The benefit for airlines using ACARS is the ability to relay and receive real time operationally critical information, be it weather updates, revised flight plans, NOTAMs or constant engine monitoring by Company Operations Centre.

Information is sent by the aircraft as a data packet, the transmission of which incurs a cost, levied by the datalink service provider (or DSP).
Two companies dominate the ACARS market; ARINC, and the European consortium of SITA.

Despite its obvious utility, Jetstar’s low cost rivals such as Virgin and Tiger have opted not to employ ACARS on their respective fleets.

Jetstar did however, but soon the company’s management examined this recurring expenditure and decided, for a modest capital outlay, it could develop and deploy its own JetstarACARS, or JACARS, system and no longer pay for the messages sent back and forth between its fleet and the ground.

In 2006, it contracted Melbourne based Aviation Data Systems to design for Jetstar its very own Private ACARS Ground Network (PAGN), consisting, as of its October 2007 launch, eight VHF ground stations located primarily up and down the Eastern Seaboard in locations as diverse as a panel beater’s roof and a roadhouse in Roma, Queensland.

Overseeing its introduction was Jetstar CIO Stephen Tame, who outlined the benefits-and challenges-of creating an in house ACARS system from scratch. He described one of the biggest hurdles was overcoming ingrained resistance from Airbus.

Different manufacturers have different approaches. Boeing have left their systems pretty much open, so you can register locations and frequencies inside the Boeing. Airbus tried to be smart, thinking “we’ll create a single map of what the world is”. So what they’ve done is coded, for all of the countries in the world, the SITA and ARINC frequencies, which they’ve locked off as a world map.

Every airline gets a copy of the world map for the A320, which seems to make sense. Until someone like Jetstar comes along ands says “Hang on, we want to become a data service provider as well and want to get ourselves on the world map” and Airbus says “We didn’t think there’d be anyone else doing this apart from SITA or ARINC.”

With JACARS in place, Jetstar was able to collect, analyse and store data at zero cost. This information was used by the airline
Bernard Spector, Jetstar’s business process optimisation manager, deals with JACARS end product: data.

In tailoring the system to the airline’s needs, the airline is able to harness greater amounts of useful, operationally specific information. “The types of data coming from the aircraft can vary enormously but it will always be things like what time it left the gate, what time it touched down, aircraft position reports and airline admin data. We get enormous amounts of data about how the engines are performing, which is used for troubleshooting.

We’re also able to send that information directly to the company who manages our power-by-the-hour. We get an enormous amount about fuel which is used for optimization, and we do a lot of work in terms of comparing what the aircraft is doing compared to what it should be doing. In short, it’s around engines, fuel and times.”

With the transmissions costs eliminated, the airline is able to expand the number of messages types it is able to send, from JACARS equipped Airbuses, from just four via ACARS, to over 14 under its successor.

Another benefit of this expanded data stream is pointed out by Stephen Tame. “We also have another system called Airman, a product offered by Airbus, it takes feeds off the aircraft and does predictive, analytics for aircraft maintenance so the whole idea is you can predict something before the problem occurs and pre position engineering. One of the problems in turning on Airman is the significant cost in data transmission because it chews up a lot of data, whereas in our case, it doesn’t’ represent a problem because I don’t pay anything for data.”

At present, JACARS covers Jetstar aircraft operating only in Australia. The high volume of Jetstar’s domestic services easily justifyied the capital outlay for the PAGN, but for the international fleet, the business case was somewhat more marginal.

However, there are proposals to introduce similar systems to Jetstar subsidiaries in Asia. As for now, whenever a Jetstar A330 travels beyond Australia, and the reach of the JACARS network, its data transmissions are handled by a hybrid system which switches from JACARS to ACAIR’s ACARS, with its associated message costs picked up by the airline.

JACARS- THE FUTURE

As worldwide air traffic increases, ACARS’ inherent bandwidth constraints will see it unable to transmit steadily rising amounts of datalink communications.

Airlines in the North America and Europe are looking to a replacement communications and reporting system for their aircraft, in parallel with larger changes being wrought by adoption of a new air traffic management regimes in the Eurozone and US.

“We don’t mind investing in technical innovation if it’s going to give us a better return.” – Jetstar’s CIO Tame

As Tame explains, “We may move the network from being an older style ACARS network to VHF Data Link (VDL) Mode 2. Basically, it’s about four times faster based on the increase in bandwidth you can get and it communicates on one frequency worldwide, so rather than like ARINC having a frequency and Jetstar having a frequency, with VDL mode 2 is, there’s only one frequency. And all of the data packets are encoded with a VDL mode 2 ‘key’, which means everybody’s using the same frequency and what separates one from the other is the key embedded in the data stream.”

To date, the Jetstar remains unique as a data service provider and the airline will happily continue to derive maximum benefit from JACARS, whose outlay was amortised in just two short years.

A concluding remark from Jetstar’s CIO Tame perhaps best sums up this low cost airline’s attitude to capital intensive outlays such as RNP-ARand JACARS:

“We don’t mind investing in technical innovation if it’s going to give us a better return.”