Editor’s Note: Software Standard

By Bill Carey | June 1, 2008
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Aerospace, like medicine, is an inexact science. The best-laid plans and remedies may not work as hoped or expected. Witness Boeing’s latest postponement of the 787 Dreamliner debut, calling into question its new business model of outsourcing the design and production of major structures and systems.

Airbus CEO Tom Enders probably said it best. Asked about the woes of the 787 program during the Singapore Airshow in February, Enders was reminded of the similarly painful birth of the A380, delivered to its first customer 18 months late. "It just tells you it’s not a piece of cake developing, industrializing, these aircraft, these high-technology machines," he said.

Technological challenge is rooted in standards development. In my previous dispatch, I reported on the unrequited expectations of the Unmanned Aircraft Systems community to gain speedy access of its flying machines into the National Airspace System. RTCA Special Committee 203 had hoped to produce Minimum Aviation System Performance Standards for unmanned aircraft in the next four or five years, including "sense-and-avoid" requirements. It’s looking now like a decade would be more accurate, although that’s a worst-case scenario.

RTCA special committees, staffed by government and industry volunteers, develop consensus-based recommendations that are used by FAA for policy and program guidance and by industry for development and investment decisions. This month’s column concerns SC-205 (jointly with EUROCAE Working Group 71), which has been slowed by a year in producing an update to DO-178B, the accepted standard for certifying avionics software. That update, when it comes, will be called DO-178C.

"Our goal was to make modifications to DO-178B and address technology-specific issues with supplements to DO-178C," explained Jim Krodel, SC-205 co-chairman. "So our deliverables are DO-178C and associated supplements, and our original schedule was to be completed by the end of ’08. That is not going to happen now. We expect to be done by the end of ’09 now. The update has taken longer [than anticipated] and we need a bit more time."

In addition to updating DO-178B, the committee is updating its ground-based complement, DO-278 — "Guidelines for Communication, Navigation, Surveillance and Air Traffic Management Systems Software Integrity Assurance" — part of the reason for the schedule stretch, Krodel said. DO-278 was not part of the committee’s original Terms of Reference.

"Originally, we had only considered DO-178 changes," Krodel said. "As we got into it, the ground-based community had attended a committee meeting and said, ‘hey, look, DO-278 is attached at the hip with -178. If we’re going to change -178, we should also be changing -278.’ We went back to RTCA and EUROCAE and requested that we add -278."

The development of supplements to DO-178B also has consumed more time than originally planned. There will be four supplements, addressing tools, formal methods, model-based design and object-oriented technology. These are addressed in the existing standard, "but only in a very general sense," Krodel said.

That a standard developed (or updated) by committee is delayed comes as no surprise to Tony Baghai, co-founder and president of HighRely Inc., of Phoenix, and coauthor of "Avionics Certification: A Complete Guide to DO-178 and DO-254." Baghai, who has followed the document releases, noted that SC-205 "kind of reversed back 180 degrees" from potentially combining DO-178 and DO-278 to retaining both documents. But he judged the impact of the overall delay on industry to be minimal, as relevant guidance already exists in different formats such as FAA Certification Authorities Software Team (CAST) position papers.

"I believe that even though the delay is occurring, it is not halting the industry in any way," Baghai said. "Luckily, there is not going to be a complete rewrite of DO-178B. DO-178B will still be applied, it’s just that it won’t have those new appendices; it won’t have those new areas of clarification that are currently in writing in different formats. Whether it’s issue papers, or whether it’s in CAST papers — they’re available."

Krodel said SC-205/WG-71 was scheduled to meet this month in Toulouse. The expectation was that it would complete major edits to DO-178C, leaving the balance of its work on the supplements.

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