A CARS over IP (AoIP) and broadband connectivity represent an opportunity for aircraft and engine data to shift from traditional ACARS VHF, HF, and safety SATCOM connectivity to more efficient networks, to help preserve the limited bandwidth of traditional networks so they can continue to provide highly reliable communications services for operational- and safety-critical airline information.
AoIP also leverages the advantages of ACARS by exploiting the growing availability and decreasing cost of broadband cellular connectivity on the ground, and IP-capable SATCOM connectivity when airborne. The specific mechanisms vary by aircraft and the type of system used, but in general, standard ACARS 618 messages are encapsulated in IP messages between the aircraft and ground-based message handlers for processing.
Because AoIP uses broadband IP communications, which have a much higher effective throughput than VHF and HF, it is a highly scalable long-term solution. And that’s important, because one particular benefit of AoIP is the ability to offload the growing volume of aircraft operations ACARS information from VHF, HF, and narrow-band safety services SATCOM, which do not have the network performance requirements that dispatch-critical or ATS ACARS applications demand.
This means that airlines that have seen costs spiraling as a result of growing aircraft operations data volume could see cost savings by moving aircraft operations ACARS messages to AoIP, which is often delivered at a flat rate.
Its champions say that segregating the use of AoIP for large aircraft operations ACARS applications and using VHF, safety services SATCOM, and HFDL for airline operational critical ACARS information offers airlines proven VHF and SATCOM safety services connectivity for operational and safety critical ACARS information. In addition, AoIP data can be integrated directly into an airline’s existing ACARS infrastructure with no ground side automation changes.
Airlines have grown to depend on ACARS information to reliably operate and dispatch aircraft. In fact, it can be argued that ACARS has become “dispatch-critical” for airline operations. Airlines will rely on VHF or HF ACARS communications for safe and reliable operations for the foreseeable future, although the need to improve the performance and capacity of traditional ACARS networks will continue as the volume of aircraft operations traffic from next generation aircraft increases.
In a September 2021 white paper on the impact of aircraft information data, Collins Aerospace pointed out that if forecasts become reality, demand will soon outpace VHF and HF capacity, and that in some regions, capacity limitations are already impacting operations. Its analysis of traffic on its ACARS network, GLOBALink, to compare aircraft operations data — in this case the OEM/Engine Digital Flight Data (DFD) application — among aircraft types demonstrates the difference in DFD ACARS volume among older and newer generations of aircraft, with newer generation aircraft generating significantly more DFD data.
Collins Aerospace’s projection of new-generation aircraft growth shows a significant increase in the percentage of new-generation aircraft compared with “legacy” aircraft over the next 15 years, when the new-generation aircraft fleet is projected to grow from 9% to 57% of all operational airline aircraft, as older aircraft are retired. With these aircraft generating significantly more AI ACARS data, there will be continued stress on VHF ACARS capacity without any change.
Indeed, to examine the stress that the growth of new generation aircraft might put on VHF capacity, Collins conducted an assessment of VHF traffic growth over the next 15 years using the new-generation aircraft growth estimate, considering ACARS growth with and without AoIP for aircraft operations ACARS information.
The assessment shows a potential growth factor of up to 2.4 times that of 2019, pre-COVID levels of VHF-based AI traffic without considering a migration of AI traffic to AoIP. It also shows that AoIP has the capability to preserve VHF capacity for critical airline operations and air traffic services by migrating aircraft operations ACARS applications away from VHF.
“The forecast shows that strong market adoption of AoIP would result in nearly half the VHF ACARS traffic over the next 15 years,” according to Collins. “While we expect VHF traffic will grow slightly as new aircraft are introduced, it could be much less dramatic with the use of AoIP. This would equate to improvements of performance to the datalink network.”
Ian Galloway is head of connected aircraft enablement services at Collins Aerospace, which has offered services since the late ‘70s to enable ACARS messaging to be processed. In the last five years, it has offered the technology to enable ACARS messaging to be sent in IP format.
As Galloway pointed out, ACARS is simply a message protocol, and IP is the communications protocol through which it is transmitted, meaning that ACARS messaging can be transmitted over IP-based channels such as cellular and broadband SATCOM, in addition to existing ACARS networks such as VHF. This essentially allows more value by expanding the networks available for ACARS messaging.
“Indeed, both Boeing and Airbus have been pushing hard for this, and what we’ve seen is significant technology capability leaps in recent technical insertion points. We are seeing a lot of interest because of the new aircraft variant types, and the challenge of managing the volume of generated data from those aircraft is huge, while at the same time protecting the VHF network, which must continue to be able to provide safety critical service. Takeup of ACARS over IP is therefore being driven by the airline industry’s investment strategy in modern aircraft,” Galloway said. “As a communications technology provider, we have seen ACARS over IP grow, and we see it as simply extending an airline and its flight operations department’s capability as it leverages an airline’s investment in connectivity in other areas.”
Discussing the merits of equipping an aircraft with AoIP, Galloway conceded that the case for equipage is a detailed and complex process for any airline: “It’s a highly complicated argument — anyone can appreciate that putting new avionics on an aircraft needs a business case. The devil is in the details, and depending on what existing avionics you operate, what will ACARS over IP enable, and what will it not enable, will need examining.”
The upside is that AoIP can be a gamechanger in terms of how the technology allows an airline to increase its operational efficiency. Collins sees itself as an avionics supplier and communication services provider whose focus is essentially consultative and highly niche to enable that value to be delivered.
“One thing is for certain — an airline’s flight operations and IT department need to be fully engaged. And while a large airline has the capability to easily understand what the transition will mean and what eventual capability the technology will offer, a smaller airline will almost certainly need many more questions answered and a high level of handholding delivered through a more consultative approach by the supplier,” Galloway said.
From a services perspective, advanced aircraft such as the A320neo and A330neo are equipped with line-fit avionics, which makes the addition of ACARS over IP much less complicated. “Obviously we see a much slower uptake in terms of the aftermarket,” Galloway said. “What we want is for a flight operations department to integrate its traditional ways of working with ACARS over IP. After all, they have built procedures about how data is collected, and all of that has been built around a particular performance profile. So our focus in 2022 will be tweaking and finessing systems as needed so an airline can get the performance it needs. We’ll also be talking to our OEM partners and listening to what they plan to focus on and how we can drive similar standards and protocols. What we would like to make sure of is that ACARS over IP does not fragment and that there continues to be some level of standardization in the use of this technology.”
Murray Skelton is senior director of international sales at Teledyne Controls. For Skelton, the chief value of ACARS over IP is that although ACARS messaging has been around for many years, the use of the IP protocol for ACARS means an airline can start to use networks it could never previously use.
For example, legacy ACARS networks require significant ground infrastructure to provide coverage around the world. As a result, for some operators ACARS coverage can be limited depending on geographical operation. However, with AoIP, ACARS data can be sent over IP networks such as cellular. Skelton said it comes as no surprise that the global cellular radio networks have far greater ground network coverage than the current ACARS services. What’s more, he said, is that the ground cellular networks are scaled to provide voice and data services to millions of devices, and the IP data bandwidths they provide are thousands of times greater than ACARS message bandwidths.
“The scalability and capability of IP networks over classic ACARS is such that networks like cellular also remove some of the ACARS usage limitations in terms of cost and message volumes,” he added. “Cellular data tariffs, roaming costs have been reducing for many years as technology refreshes, while IP bandwidth and availability has been growing exponentially. So not only does ACARS over IP increase the availability of the ACARS service, it also greatly reduces the data usage costs and allows more airlines to use it for many more operational tasks.”
Teledyne has long experience with ACARS, having been one of the original manufacturers of the first ACARS management units. Its cellular WQAR (wireless quick access recorder) equipment, the GroundLink Comm+, is installed on about 70% of the current global passenger aircraft fleet, and this technology can also deliver an ACARS over IP service for GroundLink customers. Teledyne has around 1,000 commercial air transport aircraft today either actively using or installing Ground Datalink, its AoIP over solution on its GroundLink Comm+ system. It also provides an option to use other IP networks for AoIP and AID+ connectivity through the GroundLink, such as Ka and Ku broadband IFE SATCOM, which in combination with cellular provides AoIP in all flight phases, using low-cost high-bandwidth IP networks.
Skelton pointed out that IP technology for ACARS also provides additional advantages over the current ACARS legacy systems. In today’s world, data cybersecurity is rightly a serious concern for all airlines. AoIP takes advantage of IP security technology such as PKI VPN tunneling to ensure that, unlike classic ACARS, all the AoIP messages are encrypted end to end, providing a much more secure messaging solution for aircraft operations.
In 2022, Skelton foresees a huge resurgence in airline interest in AoIP and aircraft IP connectivity in general. Airlines are looking to 2022 to get their operations back to pre-COVID levels, and operational cost reduction will be key as their recovery begins in earnest. In addition to recovery, the airline industry is facing new challenges such as new operational carbon reduction targets. To achieve these targets, airlines will need to focus on operational efficiency, and much of that will require more and better operational data monitoring driven by new connectivity solutions such as AoIP and real-time IP connectivity solutions.
Skelton predicts a very different uptake profile in 2022 for AoIP and aircraft IP connectivity solutions in general: “The 2021 recovery did not come back as expected in terms of traffic growth, although new airline business for Teledyne in the later part of 2021 demonstrated the growing confidence of our customers for a 2022 recovery, indicating that solutions like ACARS over IP are very likely to be a growth market.”
Euan Mitchell is senior product manager at SITA’s AIRCOM Cockpit Services. He sees huge benefits of encapsulating ACARS messages sent over IP networks, and quite a few of SITA’s customers have already gone in this direction or are seriously considering it through trials or through targeted deployments on sub-fleets.
He points out that ACARS as a messaging protocol is deeply embedded into an airline’s operation, touching almost every department of the airline and integrated into many back-office systems and processes that airlines use to run their operations. “This means that while the onboard changes required to implement ACARS over IP need to be carefully considered, from a ground perspective, keeping ACARS as the language an airline is used to speaking means there is little to no ground integration to consider,” Mitchell said. “As a communications service provider, we are able to deliver AoIP messages in exactly the same way to our customers as we do ACARS over VHF or satellite, through the same infrastructure, connectivity and to the same host application on the airline side. The simplicity of this is a big win for the airline.”
He said there are several flavors of AoIP solutions now coming out of the major airframers, and that the early adopters of such solutions did so (and are still doing so) on a retrofit basis. “This means they have had to craft a business case, which makes sense to the purse-string owners within the airline, to perform modification to the aircraft. Depending on the solution, this can in some cases be relatively simple and affordable.”
The successful cases SITA has seen with its customers, according to Mitchell, have been based around several benefits:
In terms of expansion of ground coverage, today most airlines base a lot of the aircraft turnaround processes on ACARS messaging. If an airline is flying to an airport that does not have VHF radio coverage, or is parked at a gate that is blocked from coverage, it has to resort to manual processes, which is painful, Mitchell said, and also inefficient in both time and cost. So connecting the aircraft to terrestrial cellular (3G/4G/5G) generally provides great coverage and enables a consistent ACARS-based turnaround process across the airline’s network.
Mitchell said this expansion of coverage also has benefits to the communications service provider, in that a VHF/VDL radio does not have to necessarily be deployed in airports where it’s not economically viable. “We have a great example of this with our customer Cebu Pacific in the Philippines. They fly to loads of airports where it is just not feasible to deploy a radio station. They deployed ACARS over IP (terrestrial cellular) where there is good coverage in the Philippines; and their aircraft can now connect at all their airports. That’s a big win.”
In terms of higher bandwidth, Mitchell said, “It’s quite amazing what the airline industry and communication service provider community have achieved over the decades, with 2.4 kbps of Very High Frequency radio throughput, and the value this has generated for the industry; but IP networks change the game, they basically put us into a place of almost unlimited capacity.”
This is good for two main reasons, according to Mitchell: First, the airline can now turn on everything. There is almost no limit now to what an airline can decide to offload from the aircraft on the ground, which previously was limited by the physics of the networks being used. The other advantage is cost, with the physics of the networks also dictating the cost of using the networks. “We effectively have to price consumption in a way that does not encourage levels of usage that the network can’t support. Enter IP, and we can move to pretty much unlimited levels of consumption for a fixed price, which supports the airline’s business case,” he said.
Also, AoIP solutions generally are created with security in mind from the beginning, during the design phase, which means they are highly secured, using things like VPN and Public Key Infrastructure (PKI), while adding an IP network into an overall communication ecosystem, or “network of networks,” provides greater resilience in that if one network fails, there exists another chance for the aircraft to connect.
For Mitchell, there is one final benefit: IP networks will help the industry manage growth. “The topic of growth is not something that has really been labored over the past 24 months, but the challenge of managing growth never really left us,” he said. “Modern aircraft consume more than their predecessors, the use of operational connected applications is rocketing (e.g. graphical weather applications and fuel optimization applications), and there are new air traffic control features coming too, like trajectory-based operations. All of this means we need more capacity — and performance — in our networks. And using IP, particularly to move “non-safety” or non-ATC messages off the existing and approved communications networks, is going to benefit the whole community.”