The U.S. Defense Department (DoD) and world militaries are facing growing parts obsolescence problems in their air fleets. Airplanes are flying decades longer than originally expected and aging avionics systems require attention. In recent years DoD has adopted an open systems strategy for designing and upgrading avionics to combat obsolescence and reduce lifecycle costs.
What's in a name?
Everyone wants openness, but perceptions of it vary. As the National Research Council (NRC) has pointed out, definitions range from using open-standard interfaces at almost every hardware and software level to using them only at the higher levels. NRC also noted a distinction between "open" and "modular," even though the DoD's version of openness, the Modular Open Systems Approach (MOSA), combines the terms and closely resembles integrated modular avionics (IMA). At the end of the day, however, an IMA cabinet hosting more than one application on shared resources is itself another box which may be integrated into an older, federated architecture.
"Open systems" is an amorphous term, says Robert Dewar, chief executive officer and president of AdaCore in New York. The company provides the GNAT Pro Ada 95 compiler and development environment used with the mission processor on the C-130 Avionics Modernization Program (AMP). Although openness is sometimes associated with open source, open architecture is typically used to talk about open interfaces, he says. Openness is also a relative term: architectures can be more or less open, depending on the number and importance of the standards they adopt. Based on an upgrade program's fleet configuration and budget, designers may aggregate many functions in an IMA approach or insert some new avionics boxes into an existing distributed architecture with communications over standard interfaces. Both routes can be open.
Milwaukee-based Astronautics Corporation of America, which follows MOSA requirements and supplies IMA-based network server systems to the Airbus A400M, takes a broad view of openness. If the aircraft is the top level and you buy boxes from Rockwell Collins, Honeywell, and Astronautics which work together, communicate over standard interfaces and can be updated by the user with other companies' products, that's open, says Dan Wade, Astronautics vice president of business development.
"Open doesn't necessarily mean that you have to have everything in a single host," says Frank Wilcox, director of technical sales for Honeywell's Integrated Systems unit in Pheonix. "It implies more [the use of] communications standards that allow communications between LRUs [line replaceable units] in a language that everybody understands." IMA was influenced by the desire to reduce the number of LRUs on an aircraft, Wilcox explains, thereby reducing the failure rate as well as the weight of the avionics. He traces the company's concern with time and space partitioning at least as far back as the B777's AIMS cabinet. Among its current military programs, Honeywell provides the P-8's versatile integrated architecture (VIA) cabinet, which hosts functions such as graphics generation.
Wind River, an ARINC 653 operating system supplier to the C-130 AMP and other programs, defines open more narrowly. "Federated architectures are simply proprietary solutions in proprietary boxes linked together in a loosely coupled string of connection technologies," asserts Chip Downing, senior director of aerospace and defense business development for Wind River in Alameda, Calif. "IMA and ARINC 653 are truly more open."
Is there a point of diminishing returns? While small unmanned aerial vehicles (UAVs) may not be able to meet consensus-based electrical and mechanical standards, they may be able to employ open standards for key interfaces in the software design, says Tony Johnson, director of the Government Systems Architecture Organization at Rockwell Collins in Cedar Rapids, Iowa. Furthermore, although military data in an avionics module must be protected, military avionics can utilize open standards at the key interfaces, he says. He describes key interfaces as those connecting to components which are included in a program's lifecycle support plan. It would not be cost-effective to pursue openness below this level, he says.
The fundamental rationale for openness is higher deployed capability, which reduces the demand for system upgrades and therefore lowers lifecycle costs, Downing says. He asserts that "open-architecture systems have saved the governments of the world billions of dollars and have enabled a wider supplier ecosystem that... competes for platforms based on price, functionality and performance vs. historical contract awards."
Rockwell Collins' open architecture upgrades have saved the government money, Johnson says. The U.S. Naval Air Systems Command has data showing cost savings on the company's CNS/ATM upgrades across platforms such as the P-3, C-2A, E-2C, and CH/MH53E. The cost decreased on successive aircraft because Rockwell Collins employed a common approach, he says. "Whether you install software functions on one LRU or distribute the software functions across multiple boxes doesn't matter." The key to Rockwell Collins' openness approach is modularity on the software side combined with a partitioned operating system. That means breaking the software up into different software functions which are partitioned based on safety criticality, security criticality, technology refresh rates, variability isolation, and organizational constraints. The software modules are designed to be as self-contained as possible and meet open standards at key interfaces.
C-130 and openness
The world's enormous C-130 fleet has seen standards-based upgrades at both the integrated and federated architectural poles. The U.S. Air Force's C-130 AMP program opted for a highly integrated approach, while other upgrades have taken more distributed approaches. Major avionics houses support both.
Boeing uses an "open-systems architecture and modular design" in the C-130 AMP program, explains Jeff McDaniel, the program's senior manager for weapon systems modernization, strategy, and growth. The goal is to be able to incorporate new equipment as long as the technology insertions use one of the standard digital bus or video interfaces. Boeing actually plugged the C-17's commercial-off-the-shelf (COTS) weather radar into the C-130 AMP systems integration lab and was able to display and manage the sensor with minimal modifications to the core software.
AMP today covers 221 C-130 combat delivery aircraft. The common avionics subkit includes the main instrument panel color liquid crystal displays (LCDs), mission processors, and radios. At the heart of the program are two VME-64x-based core mission processors provided by GE Aviation. This resource hosts independently partitioned software applications such as the flight management system (FMS), navigation, radio communication, crew and external interfaces, display formats, terrain awareness, and CNS/ATM data link communication management functions. Boeing also developed the crucial operational flight program, "glue" software that pulls all the applications together.
Astronautics is also active in C-130 upgrades. It offers a range of approaches, starting with "minimal CNS/ATM upgrades" which interface new equipment directly to legacy radios and instrument panels, Wade says.
At the next level up Astronautics offers C-130 upgrades at the LRU level. This type of upgrade can involve replacing anything from the FMS computers to the "nav or com radios," using standard digital interfaces to talk between boxes. Wade calls this level an “open, distributed” architecture. While the box-level approach may involve more weight and space than a tightly integrated approach -- because each LRU has its own memory, processor, and power supplies -- it may be easier, faster and less expensive to upgrade both in the near term and the future, he says. Astronautics, for example, went from design to certification of the first aircraft in its Brazilian C-130 upgrade -- involving CNS/ATM, communications and defensive systems modernization of the country's 21 aircraft -- n 57 weeks. The company also supplies IMA systems within its mission computer product line.