Test Systems and the New Question of Aging Avionics

By Juliet Van Wagenen | May 19, 2016
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Arne Brehmer
Arne Brehmer, aerospace manager, Vector. Photo: Vector

[Avionics Today 05-19-2016] The issues that come along with aging avionics, such as wear and tear on wire and cable, are well known across the aviation value chain. But with the Airbus A380, A350 and Boeing 787 introducing new complex avionics architectures and components, predictions about aging effects on wiring alone are no longer sufficient. Now, test system manufacturers are looking to investigate the impact of aging electronic components, such as capacitors, switches and devices in order to understand new threats and how test equipment can detect issues with new aging components going forward.

Avionics Magazine caught up with Arne Brehmer, aerospace manager at Vector, to discuss the implication of aging avionics to databus networks, such as Controller Area Networks (CAN), and how the company is looking to build new and use current test systems to address new issues.

Avionics Magazine: Can you speak to why aging avionics are becoming a concern for test system manufacturers?
Brehmer: This has been a concern for test system suppliers for some time. With more electric architecture and the usage of multiple databus systems, it is not enough just to look only on the aging or degradation of the physical layer: the wires. Aging effects the communication on the databus and leads to protocol errors that can lead to network breakdown. Moreover the higher packing of electronic components leads to higher sensitivity to aging effects.

A good example is an incident that occurred with a Virgin Atlantic Airbus A330 in which the fire detection sensors indicated a fire in the cargo area during flight that wasn’t really present In fact, the fire detection sensors had reacted to a high-humidity cargo load which finally leads to a shut down of one CAN Bus network. Therefore, the system lost its redundancy during the flight. As a result, they had to make an emergency landing and evacuation only to discover that the issue was with the sensor. The CAN Bus shut down because the robustness of the CAN network was at its limitation. If some aging effects are applied to these networks, which are at their limitations, a shutdown can occur.

Avionics Magazine: How you are designing test systems to address aging avionics?
Brehmer: Our main goal is not to design test systems that particularly address aging avionics, but with our test system or tools we can monitor at the CAN Bus system or protocols, analyze it and determine if an anomaly is being caused by a deterioration in the contact or a broken cable. Our intention is to design test systems that can alert us to indications of aging avionics. There are a lot of reasons for failure on the signal or protocol but it can give you an indication of a possible failure.

The automatic CAN Bus tester that we created alongside Airbus is one solution that can monitor these issues. With the automatic CAN Bus tester you are able to track your signal quality on a regular basis. During your normal scheduled maintenance a technician can automatically do the CAN Bus testing, which will provide a comparison over time so you can see if there have been any changes in signal quality for the CAN network and compare it to a given specification, such as the ARINC 825. The avionic engineer can then see if the signal is still within the given boundaries. This can provide an operator or technician with an indication of possible aging effects on the aircraft’s CAN Bus network.
Avionics Magazine: What are the implications of aging avionics to databus networks, such as Controller Are Network (CAN) databus communications?
Brehmer: Depending on which electronic component is affected by aging, it can lead to leakage current, increased resistance, threshold voltage drifts and self-heating. These effects have an implication on the signal quality of the CAN Bus signal. This can lead to frame errors and, it if it gets even worse, a shutdown of the CAN network occurs as with the Airbus A330 incident.
Avionics Magazine: As concerns with aging avionics focused mainly around the effects on wiring for older aircraft, how are concerns changing with newer aircraft? What new issues are you looking to address these new issues and how are you designing test systems to tackle new concerns?
Brehmer: The CAN Bus tester developed together with Airbus gives the operator or the Original Equipment Manufacturer (OEM) the opportunity to identify beginning effects of aging avionics early and to initiate corrective measures. Today, it is not used for predictive maintenance, but as soon as enough statistical data are recorded and available it will be possible to define predictive parameters.

Nevertheless, virtually everyone understands that wear and aging occurs in purely mechanical systems like bearings, engines and tires. But this phenomenon is less understood when it comes to avionics or electrical systems. From an electronic viewpoint, we tend to see component parts, especially solid-state devices and passive parts, as essentially having unlimited life. We assume they will never fail except through over-stress or physical damage.

This model can break down quickly when systems go into actual service, because of the multimode environmental forces that work in concert to bring about part failures. The specific mechanisms that occur with aging are often quite unintuitive, and this can sometimes lead to bizarre and unexpected system operation and Single Event Effects (SEE).
Avionics Magazine: What other challenges do you forsee in the test equipment landscape in the near future?
Brehmer: The major challenge ahead will be creating test equipment that can address the increasing complexity of avionic architecture, such as the evolution from federated system to Integrated Modular Avionics (IMA) to distributed IMA. Test systems will have to learn to address that higher packaging of electronic components as avionics become smaller and smaller, among others — we will have to think about appropriate cooling systems. We will have to learn to address that higher packaging of electronic components alongside the higher sensitivity to aging effects.

Avionics Magazine: How are you looking to address these upcoming challenges?
Brehmer: We have conducted some research work in which we investigated different effects of aging avionics, such as leakage current, faulty termination, increased resistance etc., on the CAN Bus communication. This will provide us with the knowledge we need about the network capabilities and robustness and how to test and identify different effects.

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