Global integration of data communications
Enhanced electronic protocols and applications will allow for our integration into the coming digitally connected global airspace.
By David Bjellos
ATP/Helo. Gulfstream G650
Senior contributor
and Dejan Damjanović
Contributing writer
Aeronautical Radio, Inc. (ARINC) was a privately held corporation started in 1929, ultimately acquired by Collins Aerospace in 2013. ARINC was founded by and comprised of various airlines and manufacturers (components and equipment) with the goal of producing sets of specifications (standards) for avionics hardware for global aircraft use.
ARINC 429 (A429)
This is the data flow within the avionics standard communications bus (ASCB) on nearly all Part 25 transport aircraft. The A429 protocol provides the digital “highway” to transfer & allocate all this data.
Communications, guidance, altitude, air data, flight management, and more are all needed to work together to accomplish a successful flight – this specific protocol was designed in the 1970’s to accomplish that goal and it remains incredibly robust.
What is unique about A429 data transfer is its simple one directional flow of bus communications data. A typical non-aviation data bus offers multidirectional data transfer between various bus points on a single set of wires – not so with A429. Pilots have long complained that the “speed” of A429 data transfer was slow; they believed that faster processors will improve performance.
In fact, the bus transmits at a fixed rate of 100 kilobytes/second (Kbps). This is by design – the limitation was agreed upon for airline use (first introduced in the 757/767 in the 1980s) for minimized weight, simplicity of design and critically ease of certification with aviation authorities. Boeing (as well as most new Airbus commercial airframes) uses a newer (and faster) version called A629 for their 777/787 airframes. For now, the vast majority of all Part 25 aircraft still incorporate A429, even if they have also installed A629.
ARINC 429 data bus inputs/outputs. The sheer volume of data derived from digital displays can overload an already task-saturated airman during normal flight. ICAO, regulators, and academia have long researched the “man–machine interface” (MMI) to identify and prioritize displayed information.
ARINC 424 (A424)
The heart of our airborne navigation database is based upon A424. It is a standard file format that specifies content and coding. It is maintained by the Airlines Electronic Engineering Committee (AEEC) and digitally published by ARINC. While not a database, it is the standard for creating and transmitting flight-critical data for end-user databases.
The A424 data for Standard Instrument Departure (SIDs), Standard Arrival Route (STARs), and approach procedures aggregate navaids and waypoints that define all segments of the procedure and how to transition from one to another. This is made possible by the concept of a “path terminator” that further expresses how a segment begins, how the aircraft is intended to navigate within/along the segment and how to prepare for the next (smart turn, flyover) or indicate if it’s the last.
There are more than 20 types of path terminators (depending upon which version of A424 you are using – and each OEM has their own defined interpretation of A424 inputs into the flight management system [FMS]). This is why aircraft with different avionics (eg, Collins, Garmin, Honeywell, Thales) will “fly” the depicted example SID slightly differently – hence the commonly heard phrase, “Why did it do that?”
Figure 1. HAILO, LAS, or BEALE are everyday examples of multiple A424 path terminators.
ARINC 840 (A840) – EFB apps
While there are more than 200 Civil Aviation Authority (CAA) member states within ICAO, there are only 3 active publishers of the A424 navigational database – Boeing’s Jeppesen, Lufthansa’s Lido, and Airbus’ NavBlue. Each of these publishers also provide proprietary electronic flight bag (EFB) apps that are designed to integrate closely with their respective commercial airliner operations (flight planning/following, crew scheduling, and maintenance operations).
These companies subscribe to the published Aeronautical Information Publication (AIPs) from those 200-plus CAAs, and transcribe them into their exclusive geospatial data warehouses, and then extract A424 databases for each flight management system (FMS) manufacturer on an Aeronautical Information Regulation and Control (AIRAC) publication interval every 28 days.
For airlines, Jeppesen, Lido, and NavBlue provide completely integrated EFB solutions that are approved through their air operator certificates (AOC), and provide real-time integrated communication with airports, global air traffic management (ATM), and airline dispatch centers to facilitate optimal (tactical) decision-making for the flight crews and their airlines.
For business and general aviation, there are general purpose EFB apps, such as ARINCDirect by Collins Aerospace and ForeFlight by Boeing, which provide flight crew-centric assistance in flight planning, navigation databases, and record-keeping.
A424 provides more than 100 types of aeronautical information for 3 distinct user groups – airports/heliports, enroute and air traffic management for end-to-end flight management. These are the most common examples for each group.
With wider availability of airborne connectivity, having integration of remote weather (such as satellite, turbulence, or Next Generation Weather Radar [NEXRAD]) ahead of planned flight routes is a significant boost to safety and efficiency. Innovative new solutions, such as SkyPath, which use crowdsourcing for turbulence data, will expand greatly non-airline metadata consumption for business aviation users.
Some of the most common A840 applications relevant to pilots are:
1. Flight Management Systems (FMS). FMS use A840 to receive and process flight plan data, aircraft performance metrics and navigation information.
2. Centralized Maintenance Systems (CMS). A840 facilitates communication between various sensors and maintenance systems, enabling real-time monitoring of aircraft health and performance.
3. Cockpit Displays. Data from avionics and aircraft sub-systems, such as engine parameters and navigation data is transmitted via A840 to cockpit displays providing pilots with a comprehensive view of the aircraft’s status. Some airframes utilize A840 to transmit real-time aircraft parameters with ACARS to OEMs or airline home maintenance base (eg, health usage monitoring systems [HUMS]).
4. Flight Control Systems. A840 is integral by transmitting information about control surface positions and aircraft dynamics, allowing for precise handling and automation (optimized with A629 for fly-by-wire [FBW] aircraft).
Beginning at the middle with SFDPS publication of AIXM, you can follow the path of digital data all the way to end-user integration. The external data is obtained through a system called AIM (aeronautical information management). Besides AIXM, other XML-based formats such as FIXM (flight information exchange model) and BXML (Briefing XML) can also be used to represent A424 data in a SWIM-compatible manner. ICAO has developed the concept of an aeronautical collaborative ring (ACR) to facilitate the exchange of information between different aviation stakeholders. SWIM is a key component of ACR.
Applications for airmen
Bravo to you if you made it this far in the article. The subject matter is dry and not easily relatable to our everyday tasks. But both airspace and avionics architecture have changed dramatically in the past several decades, with increasingly complex automation and inevitable integration of new ARINC protocols. The following will briefly describe how A424 integrates into the global (digital) airspace communications framework called system wide information management (SWIM).
The interface between A424 and SWIM involves adapting the legacy A424 navigation enterprise database format to the modern, network-based SWIM architecture using extensible markup language, or XML (.xml), the majority through the use of AIXM (aeronautical information exchange model).
XML differs from HTML in that is was designed to actively exchange data whereas HTML simply developed a particular application’s user interface (eg, text, images, symbols, bullets). XML provides rules to define any type of data (rule-based architecture vs enterprise algorithms). It is the heart of SWIM; the FAA domestic NAS version of SWIM is called enroute automation modernization (ERAM) and was fully implemented in 2015.
Data is sent over the A429 bus in a 32-bit word format, with each word representing an engineering unit such as altitude or barometric pressure. The 8-bit data label is an important aspect used to interpret the other fields of a message. Regardless of the manufacturer, each type of equipment will have a set of standard parameters identified by the label number. The other bits are reserved for Source Destination Identifiers (SDIs), data, Sign Status Matrix (SSM), and parity. SDI is used by a transmitter connected to multiple receivers to identify which one should process the message. Data is the information that is being communicated from least to most significant. SSM is used to indicate sign or direction, and data validity. Parity is error detection.
SWIM is a global concept for a harmonized, network-based architecture that enables real-time data exchange between various aviation stakeholders (air traffic control, airlines and airports).
Perhaps the most vulnerable and non-standard inputs into this SWIM matrix are country-specific AIPs and NOTAMs. ICAO, FAA, EASA, and ANSPs are working to standardize/synchronize the processing framework globally for both. It remains a challenge as each country has its own conventions for collecting and distributing the data. Incredibly, some countries still do not digitize their AIPs and NOTAMs.
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If you have more than a decade left in your flying career, you will almost certainly see the integration of supersonic commercial and business aviation aircraft, possibly flying above existing Class A airspace on direct routings. Commerce and trade will travel faster than ever globally, and full implementation of accurate and validated AIM, AIPs, and NOTAMs may be completed.
Global airspace digital communications and navigation will be available via Automatic Dependent Surveillance – Contract (ADS-C) and Controller–Pilot Data Link Communication(CPDLC), and we expect an alternative to NavStar (GPS) constellation reliability within the next 5–7 years, which is currently called alternative position, navigation, and timing (Alt-PNT).
Starlink may be the answer with their phased-array antenna. The proliferation of low-Earth orbit (LEO) satellites is growing exponentially, with 7000-plus as of this writing, overwhelmingly Starlink’s. And an LEO-based global “radar” function will become as conventional as todays terrestrial-based radar, with programs such as Aireon Air Traffic Services ADS-B surveillance.
Newer aircraft will almost certainly be predominantly FBW – and possibly single-pilot for some applications. Data communications, redundancy, and cyber security are critical to all the goals mentioned in this article. Adding to our understanding of ARINC data-comm protocols and, importantly, increasing our knowledge of the associated SWIM/ERAM conventions will better prepare today’s airmen for how this will integrate and function into our flight decks. How far we have come in such a short time is nothing short of remarkable.
Senior contributor David Bjellos has been writing for PP since 2004. He is an active airman flying a G650 based in south Florida.
Dejan Damjanović is the founder & CEO of www.thefansgroup.aero, an AIM consulting firm. He is a senior enterprise architect who has worked for Jeppesen and several firms in the remote sensing industry, specializing in the origination of ICAO AIM. Mr Damjanovic has previously held Canadian & US commercial, multi-IFR, and Instructor licenses.