In the last article on The Modern Battlespace, we looked at some of the reasons for increasing open systems adoption across the U.S. Department of Defense (DoD), why open systems are required to address today’s rapidly evolving military threat environment, and one potential solution that could enable an open system approach across allied fleets – the digital backbone.
The digital backbone environment is here to standardize how equipment is connected and modified so that it is faster and more cost-effective to install new components or functional capabilities on the aircraft. Right now, a lot of mission equipment is built to meet a specific aircraft’s needs and corresponding operational requirements. This method is a good way to develop an optimized single aircraft type but doesn’t facilitate reuse and competition for future capability. More importantly, it puts our allied forces at risk of degrading their long-held Air Dominance against emerging and rapidly evolving threats.
If we think about trying to optimize the aircraft and our fleets for quick evolution and cost-effective capability integration, we need to move to a set of common interface points between the basic aircraft systems that tend to be customized for the aircraft type, and the common functionality that we’re looking for between aircraft. In this sense, the digital backbone hopes to introduce these distinct separation points between air vehicle systems, which focus on the aircraft’s safety of flight, and the mission systems installed and embedded on the aircraft to support operations.
Using enabling technology like the digital backbone is what enables the DoD to spend f their budget dollars more efficiently on the overmatch capabilities and less on aircraft upgrades of disparate systems and fleets.
The DoD needs to optimize how they procure both the aircraft and mission systems to focus on the rapid evolution of systems through minimized impacts and changes to the aircraft given the separation of major platform sub-systems, and reuse of modular and severable building blocks within multiple aircraft types in a fleet. Using enabling technology like the digital backbone is what enables the DoD to spend f their budget dollars more efficiently on the overmatch capabilities and less on aircraft upgrades of disparate systems and fleets.
Standardization without sacrificing innovation
Achieving fast integration and fleetwide reuse requires oversight and a procurement methodology to harmonize investment and standardization of implementation approaches that extend beyond a single aircraft or a system component. This oversight (and procurement model) should scrutinize, evolve, and reinforce areas important to standardize between multiple aircraft or system components so that reuse and integration objectives are realized.
It has been said that standardization can inhibit innovation. However, there are also real costs when components are integrated that don’t follow similar standards. For example, the price can be the additional weight on the aircraft, the power conversion between 115 VAC and 28 VDC, or interface conversion computing to translate between the ARINC 429 and MIL-STD-1553 interface standards. Other impacts can include the cost and schedule of refactoring hardware and software to fit a specific vehicle context or computing infrastructure.
Finding the right balance between standardization and flexibility can be challenging or near impossible.
Finding the right balance between standardization and flexibility can be challenging or near impossible. But, by focusing on and measuring the outcome DoD is looking for, the speed of integration and reuse of components in the fleet can be significantly improved.
Organizations within the DoD, such as the Army, are working on this standardization level by establishing organizations such as the MOSA transformation office under PEO Aviation. This organization is coordinating efforts between the various aircraft program offices in the Army to apply MOSA and standardize development efforts and interfaces within their development programs.
Enabling fast integration and fleetwide reuse
The digital backbone environment is a key element in achieving fast integration since it is the common connection point between the aircraft and integrated mission systems. In a digital backbone environment, the aircraft is divided up into sections, and each major section is provided with a point of presence.
These points of presence serve up aircraft infrastructure resources, such as power, thermal management, and data communication to the sub-system components Standardizing these interfaces and creating the right underlying infrastructure will be key to the effectiveness of the digital backbone and implementing a Modular, Open System Approach across the aircraft.
The digital backbone environment is a key element in achieving fast integration since it is the common connection point between the aircraft and integrated mission systems.
For example, in the power management component of the digital backbone, we see a trend of aircraft generating a variety of power voltages at the source, depending on the aircraft generation system, which will be standardized to 28VDC at the point of presence. The point of presence will also manage and report the energy consumption for connected units so that the aircraft can control and manage its performance during different phases of flight or dynamically rebalance during component failures or damage. The benefit of this system is that it enables smaller sizing and weight of electrical systems instead of planning for the worst-case power consumption situation without rebalancing and load-shedding.
Meanwhile, the data communication component of the digital backbone is the most complex element due to variability in how systems are integrated and the variety of data communication standards available to choose from. Key criteria include:
- Amount of data that needs to be distributed
- Compatibility with existing systems
- Data formats that need to be transmitted
- Cybersecurity protection
- Data corruption prevention & delivery guarantees
Out of the key criteria listed, one of the main causes of integration cost and schedule from the data communication segment in an aircraft is the compatibility with existing systems. Frequently, data must be converted, rerouted, or reconfigured to enable new functions – or changing functions – in an aircraft. Picking a solution that uses a standard, widely proliferated interface is essential to reduce this area of frequent and often time-consuming change.
Collins is one of the key manufacturers of data distribution systems on aircraft, including ARINC664 used on large aircraft today, so developing the right next-generation solution is important. One of the most promising technologies in this space is an aerospace profile (802.1DP), based on the well-established open IEEE standard called Time Sensitive Networking (TSN). This standard began as Ethernet was being used for applications where guaranteed delivery of data and bounded latency were desirable, particularly in industrial and automotive automation.
“The big benefit [of TSN] is that it works with any system that communicates via Ethernet, which is 99 percent of the computing world” — Demildt
“The big benefit [of TSN] is that it works with any system that communicates via Ethernet, which is 99 percent of the computing world,” Demildt said. “You’ve got computing boxes at your desk that use Ethernet. You’ve got computing boxes in the air already that use Ethernet. Lots of different computing resources already talk about that standard. And, as a result, a lot of manufacturers produce it.” This wide availability and established standard for manufacturers is important for ensuring supply chain stability and product availability.
In addition, since TSN is a component of the 802.1 standards, Ethernet, cyber security hardening technologies, and techniques designed for Ethernet can be employed in an aerospace context.
With the ability to work with such a common standard, TSN allows a host of capabilities already utilized in commercial aviation to be incorporated into military aircraft more efficiently. And, since the chipset is produced broadly, it’s possible to develop new capabilities for military aircraft more quickly and less expensively – both major reasons why the DoD has increasingly shifted its focus to open systems and open architectures in the first place.
Aircraft design constraints: safety and certification
For systems that contribute to an aircraft’s ability to fly, the air vehicle system, for instance, they must operate in all conditions and provide correct data to the pilots. To guarantee this, safety processes such as SAE ARP-4761 and MIL-STD-882 govern how to analyze a system and assign a Design Assurance Level (DAL) to a system or function based on the impact it has on the safe operation of the aircraft. The higher the DAL (A-E), the greater the impact on the aircraft’s safe flight, and with each higher DAL there are additional costs to always ensure the system functions properly.
These safety processes significantly affect how an aircraft is designed and can affect how a digital backbone will enable fast future integrations if not considered at the beginning. Many past aircraft designs use separate and slower data paths for safety-critical data, while more rapid and interconnected data paths are used for mission data. Some examples of commonly sourced data include aircraft position, current time, the aircraft flight plan, or even some displays and controls used by the pilot. These types of data need to be sourced and distributed to both mission and flight critical systems.
This segregated design presents an upgrade bottleneck and constant integration headache when you need to transition data between the two types of data paths.
Collins is taking advantage of the evolution of Ethernet, with their Mosarc™ Assured Networking Solution (ANS), where the enhanced TSN features bring guaranteed data delivery within a defined latency.
Collins is taking advantage of the evolution of Ethernet, with their Mosarc™ Assured Networking Solution (ANS), where the enhanced TSN features bring guaranteed data delivery within a defined latency. These are the features on which we used to rely on the slower data paths. Moving to this standard, we can take advantage of the significant boost in bandwidth and distribute both safety-critical and mission data on the same lines.
This makes it significantly easier to publish and distribute data to all systems on the aircraft, resulting in lower SWaP and reduced integration times desired for a digital backbone. The key feature to look for is the design assurance paperwork for the digital backbone data distribution system, to ensure it has the design process and maturity to distribute data up to DAL A.
A final consideration in the implementation of an effective digital backbone system is the management of the perimeter of change on the aircraft.
Due to the safety processes described above, every time a change is made to an aircraft, it becomes necessary to verify the change does not impact critical functions. Design standards such as ARINC 653 and ARINC 661 are methods that have been used to isolate changes, but new design patterns are also being used at the system architecture level.
As stated previously, a common way this is described is a concept called Air Vehicle and Mission System split or separation. This concept separates functions that fall into one segment or another and provides isolation techniques between them to reduce the impact of changes, thus reducing cost. This concept can work in many ways but can result in issues where common system functions are shared by systems on both sides of the split, which may not be as effective.
At Collins, we are focused on the outcome of the concept and are developing system architectures with change management zones, based on the areas of frequent change. This enables us to wall off areas of the system that don’t need to change, whether air vehicle or mission systems, leading to lower overall costs and faster integrations for the future.
The digital backbone, which utilizes open standards like TSN, shows that Collins Aerospace is creating an open architecture that can be rolled out across future and enduring aircraft and other weapons systems to ensure overmatch of emerging and rapidly evolving threats. In fact, this digital backbone has been an instrumental component of a number of iterative demonstrations that have been conducted over the past few years by Collins Aerospace and a growing list that now includes nine other industry partners – enabling them all to seamlessly integrate their aviation solutions and capabilities into simulated aircraft.