The Importance of Preserving Legacy Systems in Avionics

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20 Jun, 2024

The Importance of Preserving Legacy Systems in Avionics

Futureproofing Aerospace Series. Article #1: The aviation industry is continually evolving, but preserving legacy systems remains crucial.

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The aerospace industry is continuously evolving, driven by the need to modernize, improve efficiency, and drive down costs. However, as avionics – the electronic systems that power aircraft – continue to advance, the preservation of legacy systems becomes increasingly vital. This whitepaper offers critical insights into the importance of maintaining these systems, the challenges posed by component obsolescence, and the solutions available to navigate these complexities.

Whitepaper highlights:

  1. Understand the Importance of Legacy Systems: Discover why preserving legacy avionics systems is crucial for reliability, compliance, and cost-effectiveness.
  2. Navigate Component Obsolescence: Learn about the challenges aerospace designers face due to outdated or discontinued components and how to address them.
  3. Explore Solutions from Rochester Electronics: Gain insights into how Rochester Electronics specializes in preserving and replicating obsolete components to ensure the continued operation of legacy systems.

Download the full paper below:

Like most other transportation fields, the aviation industry is subject to rapid changes and technological advancements. However, unlike other transportation fields, aviation risks are particularly high. Rather than adopting new technologies, avionics designers aim to maintain their existing systems, which have proven themselves safe and reliable after thousands of proven flight hours in real-world conditions.

But, component obsolescence threatens the continuity of legacy systems. When market forces force a component into obsolescence, short of acceptable 1:1 replacements, engineers are forced to create new designs from scratch. This process incurs significant time, cost, and risk for the avionics designer.   

At Rochester Electronics, we help designers in all industries, including avionics, skirt the challenges of component obsolescence in order to preserve their legacy systems. Read on to learn about the importance of preserving legacy systems in avionics. 

Regulatory Compliance

Before any piece of avionics equipment can find itself in production use cases, it must first pass through a stringent series of certifications. Compliance with regulatory standards, such as those set up by the Federal Aviation Administration (FAA) and the European Union Aviation Safety Agency (EASA), are used to scrutinize the equipment's performance, safety, and reliability under various operational conditions. These standards ensure that every component meets the necessary criteria to function correctly and safely within the complex environment of modern aircraft[2]. Naturally, the testing process to achieve certification is complex, time-consuming, and costly[3]

In the context of component obsolescence and preserving legacy systems, the challenge lies in the fact that even small changes to system designs can render previous certifications obsolete. When design changes are made, compliance bodies view the updated design as effectively an entirely new system, necessitating a recertification. Avionics designers then have to once again engage in the certification process from scratch, entailing huge time and monetary commitments.

By preserving legacy systems, avionics designers can avoid such changes. Instead of redesigning systems when components become obsolete, replacing those components with acceptable 1:1 alternatives can be achieved, including DO-254 minor change classification, meaning that previous certifications remain intact. 

Proven Reliability

Even outside of regulatory compliance, avionic systems must undergo extensive performance, lifetime, and reliability testing before they can be deployed in the skies.

The process of system design validation is an incredibly meticulous one. It commences in the laboratory, where designs are meticulously scrutinized, compared to internal organizational standards, and subjected to the meticulous scrutiny of governing bodies and third-party auditors. This multi-layered approach to validation ensures that when all approvals are met, designers can have high confidence in the quality and reliability of their systems[4]. Given the critical nature of aviation systems, this level of testing is non-negotiable, even for seemingly inconsequential systems.

Following laboratory testing, these systems finally make it to the skies, where they accumulate thousands of real-world flight hours over time. The thousands of flight hours translate directly into a comprehensive understanding of their behavior under diverse conditions and increased confidence in the systems.

Legacy systems have the benefit of all of this proven reliability behind them. Having experienced intense laboratory testing and then proving themselves in real-world flights, legacy systems offer aviation companies, governing bodies, and passengers the highest guarantee of reliability and safety imaginable. Should component obsolescence necessitate system redesigns, designers can no longer bank on past reliability and must instead send new systems through the same testing and validation processes[5]. Replacing obsolete components with new ones disrupts this continuity and undermines confidence in the system. 

Cost Efficiency

Significant direct and indirect financial costs are associated with replacing legacy systems in favor of new ones[6].

Directly, the physical process of redesigning systems entails investments in research and development, testing, and certification processes. The engineering hours necessary to succeed in these phases are significant. Once fully designed and through certification, the costs associated with ramping up production of a new design, including supply chain, component sourcing, and physical manufacturing, are also much higher than continuing the production of an existing system. 

Indirectly,  new systems often require extensive retraining for maintenance personnel and pilots, further adding to the overall expense. Additionally, integrating new systems into existing aircraft infrastructure often necessitates modifications to other related systems, incurring additional costs.

By maintaining legacy systems, aerospace companies can avoid these hidden costs and attain a more predictable financial landscape. With well-documented performance and maintenance histories, companies can accurately forecast maintenance costs and plan for parts replacement or system upgrades. In an industry where margins are often thin, and competition is fierce, the ability to efficiently manage resources and maintain proven, reliable systems is a significant advantage. 


One major challenge when replacing legacy components with modern technology is compatibility. 

Legacy avionics systems, including communication, navigation, and flight control instruments, are often deeply integrated with other aircraft systems and ground infrastructure. New components may not be directly compatible with existing systems in this context, leading to electrical, mechanical, and software integration issues [7]. For instance, new components might operate at different voltages or have different power requirements, necessitating redesigning power supply circuits to provide appropriate voltages and currents. These changes can affect signal integrity and electromagnetic interference (EMI), requiring circuit redesigns to accommodate accordingly. 

Software compatibility is also a critical factor in the integration process. New components often come with different firmware or drivers that might not be compatible with the existing system's software. Updating the system’s software to support new components can be complex and time-consuming, requiring engineers to rewrite or modify existing code to confirm that the system can control and monitor the new components correctly. This process involves thorough testing and validation to ensure the updated software does not introduce bugs or vulnerabilities that could compromise the system's safety and reliability.

Maintaining legacy avionics systems helps to avoid these compatibility issues and the associated costs and risks. By preserving the established integration between avionics and other aircraft systems, operators can ensure that all components continue to function as intended, maintaining safety, reliability, and efficiency.  

Technical Expertise

Finally, there is significant value to the cumulative years of experience that maintenance personnel and pilots have garnered with legacy systems. Over many hundreds of hours of direct, hands-on experience with a specific legacy solution, these individuals develop a deep and expert understanding of the systems at play, giving them more confidence in their abilities and allowing for more effective troubleshooting and repairs in the event of an issue.

The transition to new avionics systems is not a straightforward process when components become obsolete and new systems are introduced[7]. It necessitates extensive retraining for maintenance personnel and pilots, a process that is both time-consuming and costly. Maintenance crews must learn the intricacies of the new systems, including diagnostics, repair procedures, and potential integration issues with existing aircraft infrastructure. Pilots need to become familiar with new interfaces, operational procedures, and any changes in system behavior. Importantly, the retraining period can lead to a temporary reduction in operational efficiency as personnel adjust to the new systems, potentially impacting day-to-day operations.

By maintaining the continuity of legacy systems, avionics designers can maintain the expertise of maintenance crew and pilots. This means smoother aircraft operation, higher degree of safety, decreased downtime in the event of repairs, and overall more efficient operations.  


Preserving legacy avionics systems has many benefits, yet component obsolescence consistently threatens their continuity. Rochester Electronics has decades of experience addressing these threats head-on, helping customers preserve their systems and harness all of the benefits that follow. In the next article in this series, we will explore the causes of component obsolescence in greater detail.

For even more technical detail and detailed case studies, download our recently released whitepaper. 

Whitepaper highlights:

  1. Understand the Importance of Legacy Systems: Discover why preserving legacy avionics systems is crucial for reliability, compliance, and cost-effectiveness.
  2. Navigate Component Obsolescence: Learn about the challenges aerospace designers face due to outdated or discontinued components and how to address them.
  3. Explore Solutions from Rochester Electronics: Gain insights into how Rochester Electronics specializes in preserving and replicating obsolete components to ensure the continued operation of legacy systems.

Read more in the series:

Article 1: The Importance of Preserving Legacy Systems in Avionics

Article 2: The Causes of Component Obsolescence

Article 3: Customer Challenges with Obsolete Components