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4 min read

Plug and Play: The Challenge of Interoperable Airborne Software

Plug and Play: The Challenge of Interoperable Airborne Software

The process of military aircraft acquisition is a challenging one, as airborne software needs to not only be seamlessly interoperable, but also capable of supporting future needs while those needs are still evolving. So, I’ll start with two simple scenarios: when it comes to military aircraft acquisition, where are we, and where is the industry headed? 

Where are we?

Today, a service branch requests a program with specific operational domain and mission criteria. Multiple aircraft integrators compete based on the selected requirements. They in turn compete across various subcontractors for platforms, subsystems, and applications within the program. The program, if selected, begins production in tranches depending on the demand. Eventually, evolving mission requirements lead to a modernization initiative or new aircraft program and the whole process restarts. As they say in Hollywood, “let’s go back and take it from the top!”

Where is the industry headed?

Now, allow me to offer an alternative vision. A service branch requests a program with specific operational domain and mission criteria. Multiple aircraft integrators compete based on the selected requirements. Sounds familiar, but here’s where it starts to get interesting. 

Using Model-based acquisition, these integrators could look back across previous programs for platforms, subsystems, and applications that succeeded. Since they only acquire software following the Modular Open Systems Approach (MOSA), it would then be possible to select a flight control system from Program A, a cockpit display system from Program B, and pair it with a recently-developed inertial navigation system (INS) to meet the new mission requirements.

In this scenario, all this software would be readily available in a digital twin, so integrators would be able to quickly populate a model. They could, for example, import components from the existing digital twins alongside the new INS subsystem model, allowing them to evaluate performance, fit, and function for the proposed design. Essentially, they could use that model to create a prototype and verify successful software integration.

In terms of project time and cost, this could be a huge advantage. Through Model-based acquisition and digital threads, this process takes place over the course of months, not years or decades. Production could begin quickly without intensive development or retooling since the program uses proven hardware with portable, interoperable, commercial-off-the-shelf (COTS) software. 

How do we get there?

Although that vision appears on the horizon, it’s still on the other side of multiple technological evolutions. To name a few: Model Based Systems Engineering (MBSE) must reduce model complexity and maintenance, Digital Twins must enhance integration testing and simulation, and airborne software must widely adopt Open Standards that facilitate rapid software integration and reuse.

RTI Connext TSS: Interoperability with open standards

RTI contributes to all of the above initiatives, but today I’ll focus on the open standards that enable software portability and interoperability

First and foremost is The Open Group's Future Airborne Capability Environment (FACE®) Technical Standard. The FACE Technical and Business Approach addresses these topics through a set of standardized interfaces, operating environments, and business practices that call for software portability and reuse across airborne platforms. Specifically, FACE defines the Transport Services Segment (TSS) which integrates the flow of data from sensors, I/O devices, or other nodes and provides a rich, unambiguous and consistent representation of this data to applications.

RTI Connext TSS is our commercial FACE Transport Services Segment (TSS) implementation, which provides a software connectivity framework with two key methods to enable interoperability:

  1. Using open standards for data centric communication and on-the-wire data transmission
  2. Supporting cross-vendor TSS integration through the FACE Transport Protocol Module (TPM) interface.

Using open standards for data centric communication and on-the-wire data transmission

RTI Connext TSS is based on RTI Connext, making it easy for component developers and systems integrators to take advantage of both the FACE Technical Standard and the Data Distribution Service (DDS) standard. DDS defines an interface for publish-subscribe, request reply, and RPC communication, which offers loosely coupled, decentralized architecture with peer-to-peer communication for low latency while having no single point of failure. No brokers or servers are required. On the wire, DDS uses the Real-Time Publish-Subscribe (RTPS) network protocol which enables an ecosystem of implementations that seamlessly communicate by virtue of open, widely accessible standards. 

Supporting cross-vendor TSS integration through the FACE TPM interface

This blog post from August 2023 laid forth a specific challenge associated with the FACE TSS: FACE leaves the choice of a network protocol up to the software vendor, meaning that competitive TSS solutions can not interoperate purely by design. Ultimately FACE created another software module, the Transport Protocol Module (TPM), which is needed to perform the TSS-to-TSS interworking. At the time of writing, no two vendors had demonstrated successful integration between their TSS and TPMs. In fact RTI, was leading the Modular Open Systems Approach (MOSA) Risk Reduction Sub Task 1 (Task 3) by Advanced Technology International, which sought to evaluate the maturity of the TPM standard for this very purpose.

Realizing the FACE TPM Vision

In April of this year, I’m pleased to share that we achieved a major milestone in the FACE community. We successfully demonstrated a cross-vendor, cross-protocol integration solution, alongside On-Line Applications Research (OAR). My colleague John Patchin acted as System Integrator, navigating the design differences across TSS and TPM implementations. This demonstration dramatically reduces risk for complex FACE programs that need to future-proof their design for platform upgrades, or modernization based on different network protocols.


In summary, the use of open standards can help future-proof next-generation military programs. RTI Connext TSS harnesses the power of open standards from top to bottom, now with the added advantage of a demonstrated cross-vendor integration solution using the FACE TPM. Available with certified FACE 3.1 Conformance and COTS DO-178C DAL A certification evidence, Connext TSS helps reduce cost and risk for modular, open and safety-critical avionics systems. 


Please visit RTI in booth #207 at the MOSA Industry & Government Summit & Expo on June 17 -18 to learn more about our April demonstration.


For more information about Connext TSS, please visit this webpage.


About the author:

Daniel Ryan PreferredDaniel Ryan is a Product Manager for Aviation Products at Real-Time Innovations (RTI). He manages RTI Connext TSS, the leading connectivity framework for mission and safety critical Avionics systems. Daniel earned a Bachelor’s of Engineering in Computer Engineering from Vanderbilt University and is based in Louisville, KY.