AVIONICS.qxp_Finance 18/07/2022 13:53 Page 1
AVIONICS
Worldwide Aviation Digital Communications: An Overview Ken Elliott reviews worldwide digital communications in aviation. How is the efficiency of our shared airspace being improved? Find out here…
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he transition to current and future aviation digital communications involves aircraft equipage that is ‘required’, based on operational need. While newbuild platforms are ready for datalink, however, pre-owned aircraft owners are forever in catch-up mode. Aircraft have range and altitude limitations, based on their size and performance. Some are frequent users of oceanic airspace while others aren’t. Nevertheless, digital communication is not just for remote operations anymore. Significant reductions in dispatch and flight time, and fuel savings, represent a cost and time advantage to operators in domestic airspace. As preferred tracks fill up across the oceans and remote regions, popular overland routes stretch the capacity of continental air traffic. ‘Best equipped and best served’ is the way forward, and operators who invest in the equipment, training, and approvals will continue to reap the cost and time savings. Aircraft Communications, Addressing & Reporting System (ACARS) was introduced to commercial air traffic in the 1970s to satisfy a need to improve crew time-reporting. ACARS messages are short bursts of VHF data sent over the same VHF band as the radio voice on dedicated frequencies assigned to ACARS. Messages were originally available as Telex printout, digital generated voice, and then – later – routed to Flight Management System (FMS) displays for visual display. Modern ACARS messages include Out-Off-On-In (OOOI) events, flight plans, weather data, and
90 ❘ Vol 26 Issue 8 2022 ❘ AVBUYER MAGAZINE
performance status of flights. For Business Aviation, datacom has also been around for some time with its emergence in the VHF Data Link (VDL) capability engineered into aircraft VHF radios. While ACARS is character-based data, Aeronautical Telecommunications Network (ATN) is bit-based. Early versions of ATN were Mode 0 and A. The current version is Mode 2, and the future version will be Mode 3. The Modes reflect the characteristics of the data transferred – for example, you may be familiar with the terms VDL Mode 2 and ATN-B1. Note that among other characteristics (such as 4D trajectory data), the preferred ATN-B2 includes both ATN-B1 and the Oceanic/Remote Future Air Navigation System (FANS) as FANS 1/A+. Currently, ATN-B2 is the means of US FAA operating datalink services with the exception that Satcom datalink protocols are not currently in use domestically. Digital communications are not restricted to the Very High Frequency communication radio bands. Understandably, because VHF is limited to a line-of-sight range, it is ineffective over oceans and in remote regions. Both High Frequency (HF) with Selcal and Satellite (Satcom) solve that problem, and while both are traditionally voice systems, today they are datalink capable. Worldwide digital communications cannot be assessed in isolation. Indeed, the avionics suite of Communication, Navigation and Surveillance (CNS) are all integrated with respect to Air Traffic Management (ATM). For example, when www.AVBUYER.com
