Northrop Grumman Brings Real-time Virtualization to Embedded Avionics Under New Partnership

A new partnership between Northrop Grumman and Curtiss Wright targets the virtualization of obsolete military avionics systems by extracting software from legacy communications, navigation and surveillance hardware and transitioning it to modern embedded processing architectures.

This concept of using virtualization to separate legacy application software from outdated hardware has been expanding in scope, practice and demonstration for the embedded segment of the avionics market in recent years. In October 2019, the FAA published a 206-page report for avionics certification engineers entitled "USE OF VIRTUAL MACHINES IN AVIONICS SYSTEMS AND ASSURANCE CONCERNS" that provided the following definition of virtualization as: "a broad term for software used to create, from one resource, software entities so that each software entity behaves like the resource. Different types of resources can be virtualized, such as processors, memory spaces, network interface cards, communications links, or entire networks."

Effectively for avionics systems, this means that the legacy software or code that a pilot might see on an airplane as a flight path indicator on a primary flight display, can be extracted from the display and the display's embedded computing platform once the hardware becomes obsolete, and transferred to run on a newer, leaner, smarter display and faster newer processor that will allow the avionics application developer to make the flight path indicator appear or function in ways that it was unable to on the legacy computer or processor.

Interviews with engineers from the two companies provide insight into how their “ Real-time Virtualization And Modernized Protection (ReVAMP)” collaboration announced in February provides a 2020s face lift for an approach to avionics upgrading demonstrated by Northrop Grumman 17 years ago on a fleet of Group II E-2C airborne early warning aircraft operated by the U.S. Navy. A brief look back at the program’s success gives a deeper understanding of what the two companies are trying to achieve with their new ReVAMP partnership.

According to a 2005 press release provided to Avionics International by Northrop Grumman, the program was called the “Reconfigurable Processor for Legacy Avionics Code Execution” (RePLACE) avionics upgrade for the E-2C’s mission computer system that had reached its maximum processing potential and memory capacity, inhibiting its ability to integrate modern, more advanced weapons systems. Without changing any of the structural or wiring configuration featured on the mission computer, the RePLACE program replaced the Litton L-304 tactical mission computer with a commercial off the shelf (COTS) hardware.

The effort allowed the Navy to consolidate nearly 188 cards featured in the E-2C’s computers down to 4, without changing a single line of the legacy code. That change immediately improved the mean time before failure (MTBF) of the system to a predicted rate of more than 8,000 hours, reduced hardware weight from 700 to 105 pounds and decreased central-processing unit load time from more than 2.5 minutes to less than 30 seconds.

Overall, the underlying premise behind that approach was to isolate the legacy application code in the existing computers from the hardware or computing infrastructure that it was attached to and let it run unchanged on newer more modern processors.

Seventeen years later, in February, Northrop Grumman and Curtiss Wright Corp. announced a new partnership with the goal of bringing a similar approach to more embedded avionics systems currently featured on some in-service U.S. military aircraft. The partnership is anchored by single board computers supplied by Curtiss Wright and Northrop Grumman’s Real-time Virtualization And Modernized Protection (ReVAMP) virtualization software.

"ReVAMP provides a Hardware Abstraction Layer (HAL) which isolates software from physical hardware. Hardware technology refresh does not necessarily require changes to traditional mission or fight software. Instead, the HAL layer is updated for the new hardware while preserving the interfaces expected by the application software," Mike Hushion, ReVAMP/RePLACE Product manager for Northrop Grumman told Avionics.

While Northrop Grumman and Curtiss Wright were unable to provide specific in-service U.S. military aircraft programs or avionics systems and software applications that have been recently identified for the program, Hushion gave an explanation of how certain aircraft systems can become obsolete and ideal for ReVAMP's virtualization process.

Obsolescence in hardware can feature processing limitations, such as processors that simply are not fast enough to handle modern or next generation applications. Other systems can feature input/output (I/O) interfaces that are not compatible with new sensors or architectures being developed for aircraft today. As an example, in the February/March 2020 edition of Avionics International, Curtiss Wright had identified some 23,286 military aircraft worldwide were wired for the 1 megabit/per second MIL-STD-1553B data bus, a 1980s-era technology that will not permit avionics refresh programs without rewiring that can cost $750,000 per aircraft for labor and supplies alone.

At the time, the aircraft identified included 4,573 Lockheed Martin F-16 fighters, 4,000 Lockheed Martin UH-60 Blackhawk helicopters, 2,500 Lockheed Martin C-130 transports, 2,000 Boeing AH-64 Apache attack helicopters, 1,200 Boeing CH-47 Chinook helicopters, and 1,198 Boeing F-15E Strike Eagle planes.

That's why the teaming of Northrop Grumman and Curtiss Wright on the ReVAMP program could become timely if it picks up adoption across some of those aircraft that have not been integrated into an avionics refresh program since the publishing of that article.

Two engineers from both companies, Northrop Grumman’s Russ Obert, and Denis Smetana from Curtiss-Wright Defense Solutions, recently wrote an article summarizing some of the key goals of the program as well. Below, we feature an excerpt from their article to provide further detail on how the ReVAMP program works:

"The ground-breaking virtualization software is used to emulate the original system at the hardware level. New capabilities can then be added by writing new software in the legacy environment or in the modern environment. Once the system is emulated, ReVAMP interfaces provide the means for new software written in a modern language to interact with the legacy software. If, for example, an updated Identification, Friend or Foe (IFF) transponder is required, the new code used to deal with that separate transponder capability can be added to the original application code through a process called “thunking.” This process involves the software designer essentially “jumping” out of the current execution of the legacy application and OS to execute the newly written IFF code, and then jumping back into the application code where they left off, while still maintaining critical timing requirements. “Thunk” code can be used to either enhance (add to) or completely replace a section of legacy code.

A virtualized ReVAMP system is also capable of handling any I/O interfaces used by the legacy software. An I/O layer built into ReVAMP’s architecture, called Emulated I/O Services, or EIOS (see figure below), enables I/O to be remapped. If a legacy serial port interface was used on the obsolete hardware, and the new infrastructure requires data to be communicated over Ethernet, the ReVAMP I/O layer provides the necessary mapping between legacy serial and Ethernet. The I/O layer extracts data at the interface layer, so the legacy code continues to operate with no required changes."

According to a data sheet for the ReVAMP program provided to Avionics by Curtiss-Wright, several different embedded processing and computing form factors have already been identified, including VME, 3U/6U VPX and XMC boards, and a range of processor types including NXP Power Architecture, Intel, and ARM architectures.

During an interview with Avionics, Smetana also explained how the absence of the virtualization process introduced by Northrop would require avionics developers to go through a much more complicated process if they wanted to keep to transfer their application software from a legacy processing board to a new one.

“You would have to basically get a new set of hardware,” he said. “Then you would look at the board support package, and basically start re-writing all of your applications to adjust them to the APIs [application programmable interface] of the underlying hardware. Then, if there’s new I/O, you have to deal with the changes in the interfaces to those I/Os, it’s a much more complicated process if you’re unable to keep the abstraction layer unchanged the way ReVAMP does.”