Compute-intensive, high-speed, and high-bandwidth avionics and electronics are driving the demand for advanced test solutions.
Aerospace electronics and avionics continue to advance at a rapid pace, with few signs of slowing. As aerospace systems grow in complexity, engineers face myriad challenges in the test, validation, and verification of these modern devices. This trend is changing the face of test, and accelerating the need for flexible, scalable test solutions.
Aerospace organizations and workflows are putting greater emphasis on test. In fact, the demand for effective, accurate testing touches virtually every part of the end-to-end aerospace supply chain today. It is a trend with no end, fueled by the rapid pace of technology, increasing system complexity, and changing regulations and requirements.
As aerospace technologies evolve and workflows change, so too do test equipment needs. Managers are investing in purchasing new test equipment and, where possible, upgrading existing test hardware and software. Aerospace engineers have historically selected test equipment based on a system’s accuracy, speed, and acquisition cost; evolving test needs have brought about a paradigm shift, however. Today, the top considerations for selecting the optimal test solution also include: scalability, flexibility, upgradability, total cost of ownership, and support.
Legacy and modern
Aerospace and defense platforms, as well as all the critical onboard systems upon which they rely, are flying and orbiting longer than ever. The operational life of aerospace systems are being extended in response to growing industry needs and shrinking budgets. Obsolescence – not only of key parts and components, but also of test tools – is a real challenge. Engineers are facing the challenge of developing test plans for new technologies while also supporting legacy systems, such as avionics and electronics on the Boeing B-52 Stratofortress military aircraft produced in the 1950s and 1960s and still in service more than 50 years later.
Aerospace and defense engineers increasingly seek test systems capable of scaling and supporting technology updates, to avoid obsolescence events. “This approach ensures test systems that last for decades,” according to officials at National Instruments (NI), maker of test and measurement solutions in Austin, Texas. “Obsolescence management, evolving radio-frequency (RF) requirements, and design for test (DFT) challenges every test organization in the aerospace and defense industry. Organizations are transitioning from rack-and-stack box instruments and closed-architecture automated test equipment (ATE) systems to smarter test systems built on a modular platform that scales to meet current and future needs.”
Flexibility and upgradeability, as well as longevity and sustainability, are key test equipment considerations, explains Darren McCarthy, aerospace & defense technical marketing manager at Rohde & Schwarz America in Beaverton, Oregon. “Rather than locking into a dedicated test platform that may go obsolete, look to adopt a platform with an eye toward new technology insertion and one that can be maintained throughout the lifetime of the asset.” After all, he adds, “radios and avionics gear may need to be supported 15 years or longer.”
of aerospace systems, including avionics and myriad electronics.
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Evolving test needs
“The increasing use of high-speed components – including digital-to-analog converters (DACs), analog-to-digital converters (ADCs), and digital signal processors (DSPs) – has enabled modern radio and satellite communication systems as well as avionics to improve capacity, add advanced functionality, extend battery-life, and, where necessary, avoid detection,” explains David Njuguna, technical marketing manager at Tektronix in Beaverton, Oregon.
Wider bandwidth and complex modulations can increase capacity, while features like dynamic software controls and advanced DSPs can improve utility and battery life. Baseband hopping also is being used to improve radio cloaking, Njuguna says. “Because of these trends, radio development teams have often seen the need to develop custom test benches to fully characterize and validate their designs due to the lack of commercial off-the-shelf solutions for design and development. This is now changing as vendors, including Tektronix, introduce advanced test solutions – both hardware and software – to meet the evolving needs of military and aerospace design engineers.”
The development and debugging of modern communications systems, for example, often requires equipment that can support time synchronous multi-domain analysis across functional components, Njuguna says, advising designers to look for solutions that can handle this type of analysis.
“As the complexity of avionics of other systems used in aerospace and defense electronics increases, designers are looking for test equipment that allows them to see transient signals that are often hidden from view,” Njuguna continues. “Modern systems are often pushing the limits, creating a need for RF analysis products that can analyze spectrum in real-time, catching signals that might otherwise be missed. Radar engineers developing very wideband radar and electronic warfare systems need to quickly measure spectrum and characterize pulsed RF signals with minimal impairments.”
Modern spectrum monitoring and signal intelligence systems can capture, process, and record wide signal bandwidths at a broad range of frequencies, a National Instruments official explains. “Engineers need flexible software to adapt these systems to new signal types and threats.”
Accommodating changes
Changes are common and all too frequent in aerospace and defense, in which applications are increasingly influenced by rapidly evolving commercial technologies, as well as changing standards, regulations, and requirements.
“Any time changes are made to an aircraft structure, additional testing is required to verify aerodynamic performance. Low-frequency accelerometers are needed for this type of test,” says a Meggitt Sensing Systems official in Irvine, Calif. “When choosing test tools, the frequency range of interest is key and disruption to aerodynamic flow has to be considered.”
New technologies and requirements influence test, requiring adjustments by engineers, such as: “developing test plans for new technologies as they are inserted into new designs while supporting legacy systems that have been around for over 50 years,” says Rohde & Schwarz America’s McCarthy. For example, he says, Automatic Dependent Surveillance – Broadcast (ADS–B), Satellite-Based Augmentation System (SBAS), Global Navigation Satellite Systems (GNSS), and other technologies and requirements are influencing avionics test.
Military radios, McCarthy explains, are increasingly being tested to the new requirements of civil airborne software and hardware standards, such as RTCA/DO-178B, Software Considerations in Airborne Systems and Equipment Certification, and RTCA/DO-254 Level C, Design Assurance Guidance for Airborne Electronic Hardware.
Engineers are challenged with testing new multi-format radios and supporting legacy waveforms. “Civil aviation is seeing a convergence of technologies – including VHF Omni Directional Radio Range (VOR), instrument landing system (ILS), communications, weather, radar, and global position system (GPS) – into a single radio, such as the Garmin GTN series.
“To date, most avionics radios and transponders have been tested using dedicated radio test sets or test plans recommended by the manufacturer of the radio. There is a push for multi-format radios, where possible, and inclusion for new technologies that take advantage of signals of opportunity for back-up or redundancy,” McCarthy says. “One example is the military VHF/UHF airborne radios for military and state-owned applications that now must comply with sovereign civil avionics requirements, such as EU 1079/2012 (Article 9). This will require hardware and software changes to any existing military radios.”
Modularity, standards, and cost
Modern avionics include a variety of advanced technologies; high-speed serial interfaces, higher heat-producing digital instruments, electro-optics, and advanced communication standards and interfaces all play a role that influences test equipment acquisition, explains Stephen T. Sargeant, CEO at Marvin Test Solutions in Irvine, California.
“Whether it’s for the laboratory or for production test, test engineers and managers are looking for more test system and test instrument flexibility and value – i.e., test equipment acquired today can be upgraded and modified over time as my test needs evolve,” Sargeant says. “We see card modular solutions, particularly for manufacturing test, as a way to address evolving and changing test needs. To address product-specific or custom test needs, the evolution and acceptance of user-defined or user-programmable test equipment – for example, user-programmable field-programmable gate array (FPGA) solutions – offers an additional level of flexibility to address evolving/changing test requirements.”
Considerations for avionics, EW, radio, and other critical electronics testing
The rapid pace of avionics, electronic warfare, radio, and electronics advancement is prompting a shift in engineers’ top test system priorities. David Njuguna, technical marketing manager at Tektronix in Beaverton, Ore., offers the following assessment of current aerospace test challenges and considerations.
Environment/Threat Simulation: The ability to create, generate, or replicate ideal, distorted, or “real-life” signals is essential in the design, testing, and operation of electronic warfare and avionics systems. Building a threat environment involves making or recreating a lifelike radio signal as precisely as possible. This can be especially challenging, because most solutions compromise speed, bandwidth, signal fidelity, and memory. However, next-generation arbitrary waveform generators are now coming on the market that enable much easier generation of complex signals than in the past.
Spectrum Monitoring, Operational/Environmental Testing: Spectrum managers perform spectrum clearing and interference mitigation by first monitoring and verifying wide radio channels. Field testers measure a wide spectrum and generate data to determine DUT behavior in real or simulated environments. Equipment to meet these requirements can be very expensive, often requiring piecemeal solutions from multiple vendors or limited use, purpose-built equipment. Equipment now exists, from vendors such as Tektronix, to address these requirements.
Time-correlated, multi-domain measurements: Conventional analysis solutions often are limited to either frequency or time domain measurements. For more complex designs, multi-domain measurements are necessary to debug and troubleshoot design or operational problems. Engineering managers should look for instruments that offer frequency vs. time displays along with robust analysis software.
Configurable and re-configurable test equipment is a key factor, Sargeant says. “It could be done via reprogrammable FPGA-based instruments, card modular solutions where the system can be upgraded by adding/changing instrumentation, or even via software-defined test solutions by simply loading new software.”
Standards are key. “Look for solutions and tools that are standards,” Sargeant advises. “Open-architecture hardware and software solutions are a requirement if one is looking to extend test system and instrument life cycles and extract maximum value from your test investment.” At the same time, he says, “it is worthwhile to pick suppliers with long-term product support policies. It’s a well-known fact that test equipment and systems have much longer life cycles than many products that they test.”
The total cost of test includes capital costs, as well as test program development for manufacturing, which can vastly exceed the initial cost of the test equipment, Sargeant says. “As the complexity of products increases, the cost of test program development can increase; this runs counter to the demands placed on test managers to lower the cost of test.
“Advanced technologies are out-pacing test capabilities or, at a minimum, driving the cost of test higher,” Sargeant adds. Further, “shorter product development cycles coupled with more product complexity is a major challenge for aerospace engineers and managers – from both the design and the test side.”
Staying on schedule
One of the biggest challenges facing aerospace engineers seems to be schedule, recognizes Troy Troshynski, marketing and product development, Avionics Interface Technologies, a division of Teradyne in Omaha, Nebraska.
Test engineers and test organizations are increasingly under pressure to provide test systems within very compressed schedules, Troshynski explains. “They are often in situations where they must do a significant portion of the test system design even while the actual product under test (DUT) [also known as unit under test or UUT] is in its early design phase. As a result, it is often the case that some of the detailed requirements for the test system – like which avionics networks/buses are to be supported and how many interfaces to these buses are required – are not solidified even as the test system is being designed. To meet this challenge, the test engineering managers must turn to modular and flexible approaches which utilize standard platforms, like PXI and PXI Express, as well as highly programmable test instruments that are FPGA-based and can be re-configured to support multiple avionics network and bus protocols.”
Legacy avionics systems seem to be focused more on a single communications bus systems, such as ARINC 429 for commercial aircraft systems and MIL-STD-1553 for military systems, whereas newer systems are much more complex, consist of larger numbers of network nodes, and require an ever-increasing amount of data bandwidth, Troshynski says. “As a result, the latest avionics systems are based on an aggregate of several different communications networks.
Real-world test
Cost, availability, and safety make testing aerospace and defense systems in real-world settings impractical. Hardware-in-the-loop (HIL) simulation can virtually test embedded technologies like single-board computers and electronic chassis, National Instruments officials say.
It takes time and money to test and repair avionics, flight control, and intelligence, surveillance, and reconnaissance (ISR) systems in aircraft and commercial space transportation. To reduce costs and ensure system reliability, engineers use HIL simulation to test embedded systems virtually before running higher risk, more expensive, and time-consuming real-world tests. It helps ensure reliability and meet time-to-market requirements even as systems grow more complex, officials say.
Flexible software and modular, commercial off-the-shelf (COTS) hardware platforms that support a range of tests from single systems to iron birds and systems integration labs. With the flexibility and breadth of the platform, you can use the same hardware and software for not only advanced RF applications, signal intelligence, and software defined radio but also avionics systems and flight controllers.
The Embraer Legacy 450/500 Iron Bird integrated test facility features a fully equipped
executive jet cockpit with the actual hardware of an airplane installation. In a very
automated environment, not only flight controls and systems integration are tested,
but the platform can also be connected to the Full Authority Digital Engine Control
(FADEC) and aircraft electrical system, which have their own dedicated test facilities.
“Ethernet and Fibre Channel networks seem to be establishing themselves at the core of avionics networks while MIL-STD-1553 and ARINC 429 remain popular at the periphery of a lot of networks, along with CAN, Flexray, Firewire, and others,” Troshynski adds. “Because of this, when acquiring test equipment, it is important for the purchaser to consider common and industry-accepted platforms, like PXI and PXI Express, which ease integration of test equipment which much be purchased from several different suppliers.”
Given this more aggregated environment, when choosing test tools, it’s very important to look at how suppliers look at their product lines, Troshynski recommends. “Are they focused on a single avionics bus or communication technology or protocol, or are they more focused on providing an array of avionics test equipment supporting multiple protocols? Do they take advantage of a common architecture which can more easily be scaled to support new and emerging technologies as they arrive?”
In the end, aerospace and defense technology must be streamlined for speed while meeting strict quality and accuracy demands for projects that stand the test of time, says a National Instruments (NI) official in Austin, Texas.
PXI rugged PC-based platform for test, measurement, and control
National Instruments is the creator and leading provider of PXI, the modular instrumentation standard with more than 1,500 products from more than 70 vendors. The open industry standard is governed by the PXI Systems Alliance (PXISA), a group of companies chartered to promote the PXI standard, ensure interoperability, and maintain the PXI specification. PXI combines PCI electrical-bus features with the modular, Eurocard packaging of CompactPCI and adds specialized synchronization buses and key software features. It’s a high-performance, low-cost deployment platform for applications such as aerospace and defense, manufacturing test, and industrial test.
