CHARON-VAX helps the Canadian Department of National Defence keep its aircraft in the air

The Challenge

When the Canadian Forces acquired the CP-140 Aurora maritime patrol aircraft in 1980, they knew that the plane’s computer programs would require considerable maintenance. The Software Engineering Squadron (SES) was formed on August 7, 1980, to provide software support for the CP-140 Aurora. This included maintaining and designing computer programs for the Aurora’s on-board computer, for the Data Interpretation and Analysis Centre (DIAC), and for the computer-assisted training devices used by 404 Squadron.

Over the past few years, in addition to maintaining complex existing software, the SES engineers had started to develop new software, as aging components of the Aurora’s weapons systems hardware were replaced with new ones. Eventually, they decided it was time to replace the VAX 6510 and 6520 hardware, for which support had become increasingly expensive and hard to find. The machines had been running at full capacity day after day, year after year, but it was clear that they would not last forever.

Because the Aurora conducted regular surveillance missions and maintained search and rescue capabilities year-round, hardware failure could not be tolerated. Also, because Canada’s national security was involved, it was important to maintain the level of security provided by the OpenVMS operating system. The SES knew that replacing the VAXes would be a challenge; with more than 500,000 lines of code, some of which could not be accessed, migrating to another platform would be a daunting task. To complicate matters, the VAXes were also connected to a matchless Rockwell card that communicated with a Unisys system, whose programs would therefore have to be rewritten for another device…

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